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Harvey DH, Roberts CJ, Mahmoud AM, Nuñez FM, Ma Y, Fleming GP. Biomechanical and Vascular Metrics Between Eyes of Patients With Asymmetric Glaucoma and Symmetric Glaucoma. J Glaucoma 2024; 33:334-339. [PMID: 38194297 PMCID: PMC11052687 DOI: 10.1097/ijg.0000000000002363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 11/25/2023] [Indexed: 01/10/2024]
Abstract
PRCIS Corneal hysteresis (CH) and pulsatile ocular blood volume (POBV) were significantly lower in the eye with greater damage in asymmetric glaucoma, without a difference in intraocular pressure (IOP) or central corneal thickness (CCT), and no difference in elastic parameters. OBJECTIVE To compare biomechanical and vascular metrics between the eyes of patients with asymmetric glaucoma (ASYMM) and those with symmetric glaucoma (SYMM). PATIENTS AND METHODS Forty-five patients were prospectively recruited and divided into ASYMM, defined as cup-to-disc (C/D) ratio difference >0.1 between eyes and SYMM, with C/D difference ≤0.1. For ASYMM, the smaller C/D was defined as the best eye ("best") and the fellow eye was defined as the worst eye ("worse"). All metrics were subtracted as "worse" minus "best," including the viscoelastic parameter CH, and elastic parameters from the Corvis ST, including stiffness parameter at first applanation, stiffness parameter at highest concavity, integrated inverse radius, deformation amplitude ratio, IOP, CCT, mean deviation (MD), ganglion cell complex (GCC), and POBV were included. Paired t tests were performed between eyes in both groups. Statistical analyses were performed with SAS using a significance threshold of P <0.05. RESULTS For ASYMM (16 patients), "worse" showed significantly lower CH (-0.76 ± 1.22), POBV (-0.38 ± 0.305), MD (-3.66 ± 6.55), and GCC (-7.9 ± 12.2) compared with "best." No other parameters were significantly different. For SYMM (29 patients), there were no significantly different metrics between eyes. CONCLUSIONS Lower CH, POBV, GCC, and worse MD were associated with greater glaucomatous damage in asymmetric glaucoma without a difference in IOP or CCT. Lower CH and GCC are consistent with previous studies. POBV, a new clinical parameter that may indicate reduced blood flow, is also associated with greater damage.
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Affiliation(s)
| | - Cynthia J Roberts
- Ophthalmology and Visual Sciences, The Ohio State University
- Biomedical Engineering, The Ohio State University
| | - Ashraf M Mahmoud
- Ophthalmology and Visual Sciences, The Ohio State University
- Biomedical Engineering, The Ohio State University
| | | | - Yanhui Ma
- Ophthalmology and Visual Sciences, The Ohio State University
| | - Gloria P Fleming
- Ophthalmology and Visual Sciences, The Ohio State University
- Biomedical Engineering, The Ohio State University
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Chen W, Bao F, Roberts CJ, Zhang J, Wang C, Li X, Wang J, Abu Said AZM, Mayopa KN, Chen Y, Zheng X, Eliasy A, Elsheikh A, Chen S. Effect of corneal cross-linking on biomechanical changes following transepithelial photorefractive keratectomy and femtosecond laser-assisted LASIK. Front Bioeng Biotechnol 2024; 12:1323612. [PMID: 38558790 PMCID: PMC10978754 DOI: 10.3389/fbioe.2024.1323612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 01/30/2024] [Indexed: 04/04/2024] Open
Abstract
Purpose: To evaluate the change in corneal biomechanics in patients with postoperative ectasia risk when combining two common laser vision correction procedures (tPRK and FS-LASIK) with cross-linking (in tPRK Xtra and FS-LASIK Xtra). Methods: The study included 143 eyes of 143 myopic, astigmatic patients that were divided into non-cross-linked refractive surgery groups (non-Xtra groups, tPRK and FS-LASIK) and cross-linked groups (Xtra groups, tPRK Xtra and FS-LASIK Xtra) according to an ectasia risk scoring system. The eyes were subjected to measurements including the stress-strain index (SSI), the stiffness parameter at first applanation (SP-A1), the integrated inverse radius (IIR), the deformation amplitude at apex (DA), and the ratio of deformation amplitude between apex and 2 mm from apex (DARatio2mm). The measurements were taken preoperatively and at 1, 3, and 6 months postoperatively (pos1m, pos3m, and pos6m). Posterior demarcation line depth from the endothelium (PDLD) and from the ablation surface (DLA) were recorded at pos1m. Results: SP-A1 significantly decreased, while IIR, deformation amplitude, and DARatio2mm increased significantly postoperatively in all four groups (p < 0.01)-all denoting stiffness decreases. In the FS-LASIK group, the changes in IIR, DA, and DARatio2mm were 32.7 ± 15.1%, 12.9 ± 7.1%, and 27.2 ± 12.0% respectively, which were significantly higher (p < 0.05) compared to 20.1 ± 12.8%, 6.4 ± 8.2%, and 19.7 ± 10.4% in the FS-LASIK Xtra group. In the tPRK group, the change in IIR was 27.3 ± 15.5%, significantly larger than 16.9 ± 13.4% in the tPRK Xtra group. The changes of SSI were minimal in the tPRK (-1.5 ± 21.7%, p = 1.000), tPRK Xtra (8.4 ± 17.9%, p = 0.053), and FS-LASIK Xtra (5.6 ± 12.7%, p = 0.634) groups, but was significant in the FS-LASIK group (-12.1 ± 7.9%, p < 0.01). After correcting for baseline biomechanical metrics, preoperative bIOP and the change in central corneal thickness (△CCT) from pre to pos6m, the changes in the IIR in both FS-LASIK and tPRK groups, as well as DA, DARatio2mm and SSI in the FS-LASIK group remained statistically greater than their corresponding Xtra groups (all p < 0.05). Most importantly, after correcting for these covariates, the changes in DARatio2mm in the FS-LASIK Xtra became statistically smaller than in the tPRK Xtra (p = 0.017). Conclusion: The statistical analysis results indicate that tPRK Xtra and FS-LASIK Xtra effectively reduced the biomechanical losses caused by refractive surgery (tPRK and FS-LASIK). The decrease in corneal overall stiffness was greater in FS-LASIK than in tPRK, and the biomechanical enhancement of CXL was also higher following LASIK than after tPRK.
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Affiliation(s)
- Wen Chen
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - FangJun Bao
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- State Key Laboratory of Ophthalmology, Optometry and Vision Sicence, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- The Institute of Ocular Biomechanics, WenZhou Medical University, Wenzhou, China
| | - Cynthia J. Roberts
- Ophthalmology and Visual Sciences and Biomedical Engineering, The Ohio State University, Columbus, OH, United States
| | - Jia Zhang
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- State Key Laboratory of Ophthalmology, Optometry and Vision Sicence, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - Chong Wang
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - XueFei Li
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - JunJie Wang
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- State Key Laboratory of Ophthalmology, Optometry and Vision Sicence, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- The Institute of Ocular Biomechanics, WenZhou Medical University, Wenzhou, China
| | - Anas Ziad Masoud Abu Said
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - Kevin Nguelemo Mayopa
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - YaNi Chen
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - XiaoBo Zheng
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- State Key Laboratory of Ophthalmology, Optometry and Vision Sicence, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- The Institute of Ocular Biomechanics, WenZhou Medical University, Wenzhou, China
| | - Ashkan Eliasy
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
- National Institute for Health Research (NIHR) Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
- Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China
| | - ShiHao Chen
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- State Key Laboratory of Ophthalmology, Optometry and Vision Sicence, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- The Institute of Ocular Biomechanics, WenZhou Medical University, Wenzhou, China
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Roberts CJ, Knoll KM, Mahmoud AM, Hendershot AJ, Yuhas PT. Corneal Stress Distribution Evolves from Thickness-Driven in Normal Corneas to Curvature-Driven with Progression in Keratoconus. Ophthalmol Sci 2024; 4:100373. [PMID: 37868791 PMCID: PMC10587627 DOI: 10.1016/j.xops.2023.100373] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 07/13/2023] [Accepted: 07/14/2023] [Indexed: 10/24/2023]
Abstract
Purpose To introduce the novel parameter of Corneal Contribution to Stress (CCS) and compare stress distribution patterns between keratoconus (KCN) and normal corneas. Design Prospective, observational, cross-sectional study. Participants The study included 66 eyes of 40 subjects diagnosed with KCN and 155 left eyes from 155 normal control (NRL) subjects. Methods Tomography was obtained to calculate the newly proposed CCS, defined according to the hoop stress formula without intraocular pressure, R/2t, where R is the radius of curvature and t is the thickness. CCS maps were calculated from pachymetry and tangential curvature maps. Custom software identified the 2-mm-diameter zones of greatest curvature (Cspot-max), thinnest pachymetry (Pach-min), greatest stress (CCSmax), and lowest stress (CCSmin). Stress difference (CCSdiff) was calculated as CCSmax - CCSmin. Distances between Cspot-max vs. Pach-min, vs. CCSmax, and vs. CCSmin, as well as between Pach-min vs. CCSmax and vs. CCSmin, were calculated. t tests were performed between cohorts, and paired t tests were performed within cohorts. Univariate linear regression analyses were performed between parameters and distances. The significance threshold was P < 0.05. Main Outcome Measures Corneal stress parameters, corneal features of maximum curvature, minimum thickness, and distances between corneal stress parameters and corneal features. Results CCSmax was significantly closer to Pach-min (0.79 ± 0.92) and Cspot-max (2.04 ± 0.85) than CCSmin (3.17 ± 0.38, 2.73 ± 1.53, respectively) in NRL, P < 0.0001, whereas CCSmin was significantly closer to Cspot-max (1.35 ± 1.43) than CCSmax (2.52 ± 0.72) in KCN, P < 0.0001. Cspot-max (severity) was significantly related to CCSdiff in KCN (P < 0.0001; R2 = 0.5882) with a weak relationship in NRL (P < 0.0080, R2 = 0.0451). Cspot-max was significantly related to the distance from Pach-min to CCSmax (P < 0.0001; R2 = 0.3737) without significance in NRL (P = 0.8011). Conclusions Corneal stress is driven by thickness in NRL, with greatest stress at thinnest pachymetry and greatest curvature. However, maximum stress moves away from thinnest pachymetry with progression in KCN, and minimum stress is associated with maximum curvature. Severity in KCN is significantly related to greater difference between maximum and minimum stress, consistent with the biomechanical cycle of decompensation. Financial Disclosures Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.
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Affiliation(s)
- Cynthia J. Roberts
- Department of Ophthalmology & Visual Sciences, College of Medicine, The Ohio State University, Columbus, Ohio
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio
| | - Kayla M. Knoll
- Department of Ophthalmology & Visual Sciences, College of Medicine, The Ohio State University, Columbus, Ohio
- College of Optometry, The Ohio State University, Columbus, Ohio
| | - Ashraf M. Mahmoud
- Department of Ophthalmology & Visual Sciences, College of Medicine, The Ohio State University, Columbus, Ohio
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio
| | - Andrew J. Hendershot
- Department of Ophthalmology & Visual Sciences, College of Medicine, The Ohio State University, Columbus, Ohio
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Sedaghat MR, Ostadi-Moghaddam H, Momeni-Moghaddam H, Motaei S, Roberts CJ, Belin MW, Oladi Abbas Abadi S. Comparison of corneal biomechanical parameters in healthy corneas with symmetric and asymmetric bow-tie topographic pattern with inferior and superior steepening. Int Ophthalmol 2024; 44:22. [PMID: 38324098 DOI: 10.1007/s10792-024-02921-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 12/18/2023] [Indexed: 02/08/2024]
Abstract
PURPOSE To compare the corneal biomechanical parameters in healthy corneas with symmetric and asymmetric bow-tie topographic patterns. METHODS In this cross-sectional study, 144 eyes were divided based on inferior-superior asymmetry value (I-S) into symmetric (zero I-S: - 0.50 to + 0.50 D) and asymmetric bow-tie topographic patterns with inferior (positive I-S: + 0.51 to + 1.4 D) or superior (negative I-S: - 2.5 to - 0.51 D) steepening. The biomechanical assessment was performed using Corvis ST and ocular response analyzer (ORA). A general linear model univariate analysis was used to compare the parameters, while the central corneal thickness, intraocular pressure, and age were considered covariates. RESULTS Only the peak distance (PD) at the highest concavity phase (P = 0.007) and tomographic biomechanical index (TBI, P = 0.001) showed statistically significant differences between the three groups. For TBI, this difference was statistically significant between the positive I-S group separately with the zero I-S group (P < 0.001), and with the negative I-S group (P = 0.022). For PD, the significant difference was between the negative I-S group separately with zero I-S (P = 0.019), and positive I-S groups (P = 0.018). There was a statistically significant correlation between the I-S value with PD (r = 0.281, P = 0.001) and TBI (r = 0.170, P = 0.044). CONCLUSIONS Most corneal biomechanical parameters are not statistically significant compared to the zero I-S group. However, superior steepening is associated with a stiffer response based solely on the shorter PD values seen in this group, and the group with the inferior steepening shows the highest or more suspicious values based on TBI.
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Affiliation(s)
| | - Hadi Ostadi-Moghaddam
- Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Hamed Momeni-Moghaddam
- Rehabilitation Sciences Research Center, Zahedan University of Medical Sciences, Kafami Str., Zahedan, Iran.
| | - Soulmaz Motaei
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Cynthia J Roberts
- Ophthalmology & Visual Sciences and Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Michael W Belin
- Department of Ophthalmology & Vision Science, University of Arizona, Tucson, AZ, USA
| | - Samin Oladi Abbas Abadi
- Student Research Committee, Rehabilitation Sciences Research Center, Zahedan University of Medical Sciences, Zahedan, Iran
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Yuhas PT, Fortman MM, Mahmoud AM, Roberts CJ. Keratoconus cone location influences ocular biomechanical parameters measured by the Ocular Response Analyzer. Eye Vis (Lond) 2024; 11:2. [PMID: 38167119 PMCID: PMC10763366 DOI: 10.1186/s40662-023-00371-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 12/09/2023] [Indexed: 01/05/2024]
Abstract
BACKGROUND Keratoconus is characterized by asymmetry in the biomechanical properties of the cornea, with focal weakness in the area of cone formation. We tested the hypothesis that centrally-measured biomechanical parameters differ between corneas with peripheral cones and corneas with central cones. METHODS Fifty participants with keratoconus were prospectively recruited. The mean ± standard deviation age was 38 ± 13 years. Axial and tangential corneal topography were analyzed in both eyes, if eligible. Cones in the central 3 mm of the cornea were considered central, and cones outside the central 3 mm were considered peripheral. Each eye was then measured with the Ocular Response Analyzer (ORA) tonometer. T-tests compared differences in ORA-generated waveform parameters between cohorts. RESULTS Seventy-eight eyes were analyzed. According to the axial topography maps, 37 eyes had central cones and 41 eyes had peripheral cones. According to the tangential topography maps, 53 eyes had central cones, and 25 eyes had peripheral cones. For the axial-topography algorithm, wave score (WS) was significantly higher in peripheral cones than central cones (inter-cohort difference = 1.27 ± 1.87). Peripheral cones had a significantly higher area of first peak, p1area (1047 ± 1346), area of second peak, p2area (1130 ± 1478), height of first peak, h1 (102 ± 147), and height of second peak, h2 (102 ± 127), than central cones. Corneal hysteresis (CH), width of the first peak, w1, and width of the second peak, w2, did not significantly differ between cohorts. There were similar results for the tangential-topography algorithm, with a significant difference between the cohorts for p1area (855 ± 1389), p2area (860 ± 1531), h1 (81.7 ± 151), and h2 (92.1 ± 131). CONCLUSIONS Cone location affects the biomechanical response parameters measured under central loading of the cornea. The ORA delivers its air puff to the central cornea, so the fact that h1 and h2 and that p1area and p2area were smaller in the central cone cohort than in the peripheral cone cohort suggests that corneas with central cones are softer or more compliant centrally than corneas with peripheral cones, which is consistent with the location of the pathology. This result is evidence that corneal weakening in keratoconus is focal in nature and is consistent with localized disruption of lamellar orientation.
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Affiliation(s)
- Phillip T Yuhas
- College of Optometry, The Ohio State University, Columbus, OH, USA
| | | | - Ashraf M Mahmoud
- Department of Ophthalmology and Visual Sciences, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Sciences, College of Medicine, The Ohio State University, Columbus, OH, USA.
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH, USA.
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Gingras AA, Jansen PA, Smith C, Zhang X, Niu Y, Zhao Y, Roberts CJ, Herderick ED, Swindle-Reilly KE. 3D Bioprinting of Acellular Corneal Stromal Scaffolds with a Low Cost Modified 3D Printer: A Feasibility Study. Curr Eye Res 2023; 48:1112-1121. [PMID: 37669915 DOI: 10.1080/02713683.2023.2251172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 07/21/2023] [Accepted: 08/20/2023] [Indexed: 09/07/2023]
Abstract
PURPOSE Loss of corneal transparency is one of the major causes of visual loss, generating a considerable health and economic burden globally. Corneal transplantation is the leading treatment procedure, where the diseased cornea is replaced by donated corneal tissue. Despite the rise of cornea donations in the past decade, there is still a huge gap between cornea supply and demand worldwide. 3D bioprinting is an emerging technology that can be used to fabricate tissue equivalents that resemble the native tissue, which holds great potential for corneal tissue engineering application. This study evaluates the manufacturability of 3D bioprinted acellular corneal grafts using low-cost equipment and software, not necessarily designed for bioprinting applications. This approach allows access to 3D printed structures where commercial 3D bioprinters are cost prohibitive and not readily accessible to researchers and clinicians. METHODS Two extrusion-based methods were used to 3D print acellular corneal stromal scaffolds with collagen, alginate, and alginate-gelatin composite bioinks from a digital corneal model. Compression testing was used to determine moduli. RESULTS The printed model was visually transparent with tunable mechanical properties. The model had central radius of curvature of 7.4 mm, diameter of 13.2 mm, and central thickness of 0.4 mm. The compressive secant modulus of the material was 23.7 ± 1.7 kPa at 20% strain. 3D printing into a concave mold had reliability advantages over printing into a convex mold. CONCLUSIONS The printed corneal models exhibited visible transparency and a dome shape, demonstrating the potential of this process for the preparation of acellular partial thickness corneal replacements. The modified printing process presented a low-cost option for corneal bioprinting.
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Affiliation(s)
- Amelia A Gingras
- Center for Design and Manufacturing Excellence, The Ohio State University, Columbus, OH, USA
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Peter A Jansen
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Caroline Smith
- Center for Design and Manufacturing Excellence, The Ohio State University, Columbus, OH, USA
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Xu Zhang
- Center for Design and Manufacturing Excellence, The Ohio State University, Columbus, OH, USA
| | - Ye Niu
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
- Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH, USA
| | - Yi Zhao
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
- Department of Ophthalmology and Visual Sciences, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Cynthia J Roberts
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
- Department of Ophthalmology and Visual Sciences, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Edward D Herderick
- Center for Design and Manufacturing Excellence, The Ohio State University, Columbus, OH, USA
| | - Katelyn E Swindle-Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
- Department of Ophthalmology and Visual Sciences, The Ohio State University Wexner Medical Center, Columbus, OH, USA
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, USA
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Vinciguerra R, Fernández-Vega-Cueto L, Roberts CJ, Poo-Lopez A, Eliasy A, Merayo-Lloves J, Elsheikh A, Madrid-Costa D, Lisa C, Alfonso JF. Effect of intrastromal corneal ring segments on in vivo corneal biomechanics in keratoconus: 1-year results. J Cataract Refract Surg 2023; 49:1258-1263. [PMID: 37982775 DOI: 10.1097/j.jcrs.0000000000001298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 08/24/2023] [Indexed: 11/21/2023]
Abstract
PURPOSE To evaluate the 1-year effects of the implantation of intrastromal corneal ring segments (ICRS) in keratoconus (KC) on the dynamic corneal response (DCR) parameters obtained with the Corvis. SETTING Fernández-Vega Ophthalmological Institute, Oviedo, Spain. DESIGN Prospective, single-center, clinical study. METHODS Included were patients who underwent ICRS implantation for KC over a period of 1 year. On the day of the surgery and at least 6 months after ICRS implantation, the following measurements were made: corrected distance and uncorrected distance visual acuity, corneal tomography indices with the Pentacam, biomechanically corrected intraocular pressure and the Corvis DCRs (integrated inverse concave radius, deformation amplitude ratio, stiffness parameter at first applanation, stress-strain index [SSI] and the highest concavity radius). RESULTS 30 eyes were included with a mean follow-up time of 15 months. Statistical analysis showed that ICRS implantation induced significant improvements in corneal biomechanics measurements between preoperative and long-term follow-up as demonstrated by a significant increase in SSI (P = .003). To confirm that this difference was actually induced due to a stiffening between early postoperative (previously published) and long-term an additional t-test was done between month 1 and late follow-up which confirmed a significant stiffening in the value of SSI (P = .01). CONCLUSIONS Patients implanted with ICRS alone for KC showed a significantly stiffer response due to increased structural support compared with preoperative values and 1 month postoperative.
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Affiliation(s)
- Riccardo Vinciguerra
- From the Humanitas San Pio X Hospital, Milan, Italy (Vinciguerra); Surgery Department, School of Medicine, University of Oviedo, Asturias, Spain (Vinciguerra, Fernández-Vega-Cueto, Poo-Lopez, Merayo-Lloves, Lisa, Alfonso); Fernández-Vega Ophthalmological Institute, Oviedo, Spain (Fernández-Vega-Cueto, Poo-Lopez, Merayo-Lloves, Madrid-Costa, Lisa, Alfonso); Department of Ophthalmology & Visual Science, Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio (Roberts); School of Engineering, University of Liverpool, Liverpool, United Kingdom (Eliasy, Elsheikh); Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, China (Elsheikh); National Institute for Health Research (NIHR) Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom (Elsheikh)
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Hashemi H, Asgari S, Mahmoud AM, Mehravaran S, Roberts CJ. Variability of CLMI-X parameters, zonal Kmax, and single-point Kmax in keratoconus progression. Eye (Lond) 2023; 37:3197-3202. [PMID: 36918626 PMCID: PMC10564939 DOI: 10.1038/s41433-023-02476-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 01/31/2023] [Accepted: 02/27/2023] [Indexed: 03/16/2023] Open
Abstract
OBJECTIVES To compare the repeatability of Cone Location and Magnitude Index expanded (CLMI.X) parameters of 2 mm diameter zone of greatest corneal curvature (Cspot-Axi) and 1 mm diameter zone of thinnest pachmymetry (Spot-Pach) with the maximum single point keratometry (Kmax), 3 mm Zonal Kmax (Z-Kmax3), and thinnest single point pachymetry (TP) in keratoconus (KC). METHODS In this Comparative repeatability study, data from 36 eyes of 36 normal individuals and 72 eyes of 72 KC patients (28 eyes with ≤50.0D and 44 eyes with >50.0D Z-Kmax3) were analyzed. For each enrolled eye, imaging was done 6 times (3 consecutive acquisitions with a half hour break). For each parameter, the within-subject standard deviation (Sw) was calculated from the data of the six exams. RESULTS In the normal group, Cspot-Axi-Sw was different from Kmax-Sw (p = 0.0004). Also, Z-Kmax3-Sw was different from Kmax-Sw (p = 0.0297). The difference between Cspot-Axi-Sw and Z-Kmax3-Sw was statistically significant (p = 0.0482). In the KC group, Sw were significantly different between Cspot-Axi and Kmax (p < 0.0001), and between Z-Kmax3 and Kmax (p < 0.0001). In the Z-Kmax3 ≤ 50.0D subgroup, Sw were different between Cspot-Axi and Kmax (p = 0.0002). In the Z-Kmax3 > 50.0D subgroup, Sw were different between Cspot-Axi and Kmax (p < 0.0001), and between Z-Kmax3 and Kmax (p < 0.0001). Sw differences between Spot-Pach and TP were not significant in any of the study groups (all P > 0.05). CONCLUSIONS In the diagnosis and follow up of KC, the zonal averages of Cspot-Axi and Z-Kmax3 are more reliable than the single point Kmax. The repeatability of Spot-Pach is similar to TP and both variables should suit the purpose equally.
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Affiliation(s)
- Hassan Hashemi
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
| | - Soheila Asgari
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
| | - Ashraf M Mahmoud
- Department of Ophthalmology & Visual Sciences, The Ohio State University, Wexner Medical Center, Columbus, OH, USA
| | - Shiva Mehravaran
- School of Computer, Mathematical, and Natural Sciences, Morgan State University, Baltimore, MD, USA
| | - Cynthia J Roberts
- Department of Ophthalmology & Visual Sciences, Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
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Yuhas PT, McHugh-Morrison C, Canavan J, Jeyandran J, Mahmoud AM, Roberts CJ. Intereye Differences in the Clinical Assessment of Intraocular Pressure and Ocular Biomechanics. Optom Vis Sci 2023; 100:688-696. [PMID: 37639554 PMCID: PMC10662582 DOI: 10.1097/opx.0000000000002066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 07/23/2023] [Indexed: 08/31/2023] Open
Abstract
SIGNIFICANCE Clinicians and researchers will have evidence whether intereye differences confound clinical measurements of intraocular pressure or of ocular biomechanical parameters. PURPOSE The purpose of this study was to determine whether intraocular pressure and biomechanical parameters, as measured by the Ocular Response Analyzer (ORA) and by Cornea Visualization with Scheimpflug Technology (CorVis ST), are different between the first and second eye measured. METHODS Intraocular pressure and biomechanical parameters were collected from both eyes of healthy participants (N = 139). The ORA measured corneal-compensated intraocular pressure, Goldmann-correlated intraocular pressure, and corneal hysteresis. The CorVis ST measured biomechanically corrected intraocular pressure, stiffness parameter at first applanation, and stiffness parameter at highest concavity. For each measurement, a paired t test compared the value of the first eye measured against that of the second eye measured. RESULTS For the ORA, Goldmann-correlated intraocular pressure was significantly higher ( P = .001) in the first eye (14.8 [3.45] mmHg) than in the second eye (14.3 [3.63] mmHg). For the CorVis ST, biomechanically corrected intraocular pressure was significantly higher ( P < .001) in the second eye (14.7 [2.14] mmHg) than in the first eye (14.3 [2.11] mmHg). Stiffness parameter at first applanation (intereye difference, 6.85 [9.54] mmHg/mm) was significantly ( P < .001) higher in the first eye than in the second eye. Stiffness parameter at highest concavity was significantly higher ( P = .01) in the second eye (14.3 [3.18] mmHg/mm) than in the first eye (14.0 [3.13] mmHg/mm). CONCLUSIONS Although there were statistically significant intereye differences in intraocular pressure and in biomechanical parameters for both devices, the variations were small and thus unlikely to affect clinical outcomes.
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Affiliation(s)
| | | | - Joshua Canavan
- College of Optometry, The Ohio State University, Columbus, Ohio
| | | | - Ashraf M. Mahmoud
- Department of Ophthalmology and Visual Sciences, College of Medicine, The Ohio State University, Columbus, Ohio
| | - Cynthia J. Roberts
- Department of Ophthalmology and Visual Sciences, College of Medicine, The Ohio State University, Columbus, Ohio
- Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, Ohio
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Somogye RH, Roberts CJ, Spoerl E, Pillunat KR, Pillunat LE, Small RH. Estimating pulsatile ocular blood volume from intraocular pressure, ocular pulse amplitude, and axial length. PLoS One 2023; 18:e0283387. [PMID: 36952489 PMCID: PMC10035833 DOI: 10.1371/journal.pone.0283387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 03/07/2023] [Indexed: 03/25/2023] Open
Abstract
The purpose of this study was to develop a method of estimating pulsatile ocular blood volume (POBV) from measurements taken during an ophthalmic exam, including axial length and using a tonometer capable of measuring intraocular pressure (IOP) and ocular pulse amplitude (OPA). Unpublished OPA data from a previous invasive study was used in the derivation, along with central corneal thickness (CCT) and axial length (AL), as well as IOP from the PASCAL dynamic contour tonometer (DCT) and intracameral (ICM) measurements of IOP for 60 cataract patients. Intracameral mean pressure was set to 15, 20, and 35 mmHg (randomized sequence) in the supine position, using a fluid-filled manometer. IOP and OPA measurements were acquired at each manometric setpoint (DCT and ICM simultaneously). In the current study, ocular rigidity (OR) was estimated using a published significant relationship of OR to the natural log of AL in which OR was invasively measured through fluid injection. Friedenwald’s original pressure volume relationship was then used to derive the estimated POBV, delivered to the choroid with each heartbeat as a function of OR, systolic IOP (IOPsys), diastolic IOP (IOPdia), and OPA, according to the derived equation POBV = log (IOPsys/IOPdia) / OR. Linear regression analyses were performed comparing OPA to OR and calculated POBV at each of the three manometric setpoints. POBV was also compared to OPA/IOPdia with all data points combined. Significance threshold was p < 0.05. OR estimated from AL showed a significant positive relationship to OPA for both DCT (p < 0.011) and ICM (p < 0.006) at all three manometric pressure setpoints, with a greater slope for lower IOP. Calculated POBV also showed a significant positive relationship to OPA (p < 0.001) at all three setpoints with greater slope at lower IOP, and a significant negative relationship with IOPdia. In the combined analysis, POBV showed a significant positive relationship to OPA/ IOPdia (p < 0.001) in both ICM and DCT measurements with R2 = 0.9685, and R2 = 0.9589, respectively. POBV provides a straight-forward, clinically applicable method to estimate ocular blood supply noninvasively. Higher IOP in combination with lower OPA results in the lowest values of POBV. The simplified ratio, OPA/ IOPdia, may also provide a useful clinical tool for evaluating changes in ocular blood supply in diseases with a vascular component, such as diabetic retinopathy and normal tension glaucoma. Future studies are warranted.
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Affiliation(s)
- Ryan H. Somogye
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States of America
| | - Cynthia J. Roberts
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States of America
- Department of Ophthalmology & Visual Sciences, The Ohio State University Wexner Medical Center, Columbus, OH, United States of America
- * E-mail:
| | - Eberhard Spoerl
- Department of Ophthalmology, Universitatsklinikum Carl Gustav Carus, Dresden, Germany
| | - Karin R. Pillunat
- Department of Ophthalmology, Universitatsklinikum Carl Gustav Carus, Dresden, Germany
| | - Lutz E. Pillunat
- Department of Ophthalmology, Universitatsklinikum Carl Gustav Carus, Dresden, Germany
| | - Robert H. Small
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States of America
- Department of Anesthesiology, The Ohio State University Wexner Medical Center, Columbus, OH, United States of America
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Hashemi H, Roberts CJ, Elsheikh A, Mehravaran S, Panahi P, Asgari S. Corneal Biomechanics After SMILE, Femtosecond-Assisted LASIK, and Photorefractive Keratectomy: A Matched Comparison Study. Transl Vis Sci Technol 2023; 12:12. [PMID: 36928130 PMCID: PMC10029763 DOI: 10.1167/tvst.12.3.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023] Open
Abstract
Purpose To evaluate the change in corneal stiffness after small incision lenticule extraction (SMILE), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), and photorefractive keratectomy (PRK). Methods Age, gender, spherical equivalent, and central corneal thickness (CCT)-matched cases undergoing SMILE with a 120-µ cap, FS-LASIK with a 110-µ flap, and PRK were enrolled. One-year change in the stress-strain index, stiffness parameter at first applanation, integrated inverse radius, deformation amplitude ratio at 2 mm, and deformation amplitude ratio at 1 mm were compared between the surgical groups by linear mixed-effect models. Results Within each surgical group, 120 eyes completed 1 year of follow-up. The residual stromal bed (RSB) thickness and (RSB/CCTpostop) were 348.1 ± 35.0 (0.74), 375.4 ± 31.0 (0.77) and 426.7 ± 2 µm (0.88) after SMILE, FS-LASIK, and PRK, respectively. The 1-year change in all biomechanical indices was significant, except the stress-strain index with PRK (P = 0.884). The change in all indices with SMILE were significantly greater than with FS-LASIK and with PRK (all P < 0.01), except the deformation amplitude ratio at 1 mm change between SMILE and FS-LASIK (P = 0.075). The changes in all indices with FS-LASIK were significantly greater than with PRK (all P < 0.05). Conclusions Although SMILE preserves the greatest amount of anterior cornea with a cap thickness of 120 µ, this also produces the smallest RSB and the greatest decrease in stiffness. Thus, the RSB is shown to be the predominant determinant of stiffness decreases, rather than the preserved anterior cornea. We recommend using a thinner cap to achieve a thicker RSB and a lesser decrease in the corneal stiffness in the SMILE procedure. Translational Relevance After refractive surgery, RSB is predominant determinant of stiffness decreases, rather than the preserved anterior cornea.
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Affiliation(s)
- Hassan Hashemi
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
| | - Cynthia J Roberts
- Department of Ophthalmology & Visual Sciences, Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, UK
- National Institute for Health Research (NIHR) Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
- Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China
| | - Shiva Mehravaran
- School of Computer, Mathematical, and Natural Sciences, Morgan State University, Baltimore, MD, USA
| | - Parsa Panahi
- Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran
| | - Soheila Asgari
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
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12
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Reilly MA, Katz SE, Roberts CJ. Orbital fat swelling: A biomechanical theory and supporting model for spaceflight-associated neuro-ocular syndrome (SANS). Front Bioeng Biotechnol 2023; 11:1095948. [PMID: 36845176 PMCID: PMC9947460 DOI: 10.3389/fbioe.2023.1095948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 01/30/2023] [Indexed: 02/11/2023] Open
Abstract
Spaceflight-Associated Neuro-ocular Syndrome (SANS) is a descriptor of several ocular and visual signs and symptoms which commonly afflicts those exposed to microgravity. We propose a new theory for the driving force leading to the development of Spaceflight-Associated Neuro-ocular Syndrome which is described via a finite element model of the eye and orbit. Our simulations suggest that the anteriorly directed force produced by orbital fat swelling is a unifying explanatory mechanism for Spaceflight-Associated Neuro-ocular Syndrome, as well as producing a larger effect than that generated by elevation in intracranial pressure. Hallmarks of this new theory include broad flattening of the posterior globe, loss of tension in the peripapillary choroid, decreased axial length, consistent with findings in astronauts. A geometric sensitivity study suggests several anatomical dimensions may be protective against Spaceflight-Associated Neuro-ocular Syndrome.
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Affiliation(s)
- Matthew A. Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States,Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, United States,*Correspondence: Matthew A. Reilly,
| | - Steven E. Katz
- Ohio Neuro-Ophthalmology, Orbital Disease & Oculoplastics, Columbus, OH, United States
| | - Cynthia J. Roberts
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States,Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, United States
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13
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Shen SR, Fleming GP, Jain SG, Roberts CJ. A Review of Corneal Biomechanics and Scleral Stiffness in Topical Prostaglandin Analog Therapy for Glaucoma. Curr Eye Res 2023; 48:172-181. [PMID: 35929977 DOI: 10.1080/02713683.2022.2099903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
PURPOSE The mechanism of action underlying prostaglandin analog (PGA) therapy involves changes in the expression of different metalloproteases to increase permeability of the sclera and allow increased aqueous humor outflow through this alternative drainage pathway. This alteration of structure impacts cornea/scleral biomechanics and may introduce artifact into the measurement of intraocular pressure (IOP) in the clinical setting. METHODS A literature search reviewing the impact of PGA therapy on corneal and scleral biomechanics was conducted including basic studies, clinical studies with treatment naïve patients, and a clinical study examining the cessation of PGA therapy. Additional literature including engineering texts was added for greater clarity of the concepts underlying ocular biomechanics. RESULTS One study with an animal model reported significant corneal stiffening with PGA treatment. Most longitudinal clinical studies examining the effects of initiation of PGA therapy in PGA naïve subjects failed to report biomechanical parameters associated with stiffness using the Corvis ST and only included those parameters strongly influenced by IOP. One study reported a significant reduction in scleral stiffness with IOP as a co-variate, highlighting the need to account for the effects of IOP lowering when assessing clinical biomechanics. The report of cessation of PGA therapy on corneal biomechanics showed no change in corneal compensated IOP after 6 weeks, raising the question of reversibility of the PGA-induced structural alteration. CONCLUSIONS Given that the findings in several clinical studies may merely reflect a reduction in IOP, further studies are warranted using Corvis ST parameters associated with corneal and scleral stiffness. The gold standard for IOP measurement in the clinical setting is Goldmann applanation tonometry, a technique previously shown to be affected by corneal stiffness. Since PGA therapy has been reported to alter not only scleral biomechanics, but also corneal biomechanics, it is essential to consider alternative tonometry technologies in the clinic.
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Affiliation(s)
- Steven R Shen
- College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Gloria P Fleming
- Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA
| | - Shelly Gupta Jain
- Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA.,Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
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Yuhas PT, Roberts CJ. Clinical Ocular Biomechanics: Where Are We after 20 Years of Progress? Curr Eye Res 2023; 48:89-104. [PMID: 36239188 DOI: 10.1080/02713683.2022.2125530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Purpose: Ocular biomechanics is an assessment of the response of the structures of the eye to forces that may lead to disease development and progression, or influence the response to surgical intervention. The goals of this review are (1) to introduce basic biomechanical principles and terminology, (2) to provide perspective on the progress made in the clinical study and assessment of ocular biomechanics, and (3) to highlight critical studies conducted in keratoconus, laser refractive surgery, and glaucoma in order to aid interpretation of biomechanical parameters in the laboratory and in the clinic.Methods: A literature review was first conducted of basic biomechanical studies related to ocular tissue. The subsequent review of ocular biomechanical studies was limited to those focusing on keratoconus, laser refractive surgery, or glaucoma using the only two commercially available devices that allow rapid assessment of biomechanical response in the clinic.Results: Foundational studies on ocular biomechanics used a combination of computer modeling and destructive forces on ex-vivo tissues. The knowledge gained from these studies could not be directly translated to clinical research and practice until the introduction of non-contact tonometers that quantified the deformation response of the cornea to an air puff, which represents a non-destructive, clinically appropriate load. The corneal response includes a contribution from the sclera which may limit corneal deformation. Two commercial devices are available, the Ocular Response Analyzer which produces viscoelastic parameters with a customized load for each eye, and the Corvis ST which produces elastic parameters with a consistent load for every eye. Neither device produces the classic biomechanical properties reported in basic studies, but rather biomechanical deformation response parameters which require careful interpretation.Conclusions: Research using clinical tools has enriched our understanding of how ocular disease alters ocular biomechanics, as well as how ocular biomechanics may influence the pathophysiology of ocular disease and response to surgical intervention.
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Affiliation(s)
- Phillip T Yuhas
- College of Optometry, The Ohio State University, Columbus, OH, USA
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Sciences, College of Medicine, The Ohio State University, Columbus, OH, USA.,Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH, USA
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Hashemi H, Roberts CJ, Ambrósio R, Mehravaran S, Hafezi F, Vinciguerra R, Vinciguerra P, Panahi P, Asgari S. Comparative Contralateral Randomized Clinical Trial of Standard (3 mW/cm 2) Versus Accelerated (9 mW/cm 2) CXL in Patients With Down Syndrome: 3-Year Results. J Refract Surg 2022; 38:381-388. [PMID: 35686709 DOI: 10.3928/1081597x-20220329-01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To compare the long-term results of accelerated corneal cross-linking (CXL) (9 mW/cm2, 10 min) with standard CXL (3 mW/cm2, 30 min) in patients with Down syndrome who had keratoconus. METHODS In this contralateral randomized clinical trial, 27 patients with Down syndrome aged 15.78 ± 2.46 years (range: 10 to 19 years) were enrolled. CXL was performed using the KXL System (Avedro, Inc) under general anesthesia, and patients were followed up for 3 years. The main outcome measure was a change in average keratometry in the 3-mm zone around the steepest point (zonal Kmax-3mm). Secondary outcomes were changes in Corvis ST (Oculus Optikgeräte GmbH) biomechanical parameters and vision, refraction, and corneal tomography measurements. RESULTS Mean 3-year changes in zonal Kmax-3mm were not significantly different between the accelerated and standard groups (-0.06 ± 0.75 and -0.35 ± 0.94 diopters [D], respectively, P = .727). Despite the contralateral design of the study, based on most baseline biomechanical indices, corneas in the standard group were weaker before treatment. The standard group also showed significantly fewer 3-year changes in the stress-strain index (-0.11 ± 0.21 vs -0.30 ± 0.32), integrated radius (+0.99 ± 3.48 vs +3.14 ± 2.84), and deformation amplitude ratio-2mm (-1.38 ± 1.33 vs +0.30 ± 1.75) (all P < .0167). Corneal stiffness in the accelerated group was stable for 2 years, and the decline mainly occurred during the third year. CONCLUSIONS In young patients with Down syndrome who had keratoconus, accelerated and standard CXL showed a similar flattening effect. Standard CXL is better able to maintain corneal stiffness in weaker corneas. With accelerated CXL, despite stable results for 2 years, there was decreased corneal stiffness in the third year. Longer follow-up periods are warranted to study the decreased efficacy on keratoconus progression. [J Refract Surg. 2022;38(6):381-388.].
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Asroui L, Dagher SA, Elsheikh A, Lopes BT, Roberts CJ, Assouad M, Awwad ST. Biomechanical Evaluation of Topographically and Tomographically Normal Fellow Eyes of Patients With Keratoconus. J Refract Surg 2022; 38:318-325. [PMID: 35536713 DOI: 10.3928/1081597x-20220225-01] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To determine the effectiveness of parameters and indices based on biomechanical measures at discriminating fellow eyes with topographically and tomographically normal corneas in patients with keratoconus from normal control corneas. METHODS The study included 47 keratoconus suspect eyes, defined as the topographically and tomographically normal fellow eyes of patients with frank keratoconus in the other eye. Eyes were imaged using the Pentacam HR and Corvis ST (both Oculus Optikgeräte GmbH). Fellow eyes were then categorized as topographically/tomographically normal fellow eyes (TNF) and topographically/tomographically borderline fellow eyes (TBF). The ability of each of the Corvis Biomechanical Index (CBI), Tomographic and Biomechanical Index (TBI), stiffness parameter at applanation 1 (SP-A1), and stress-strain index (SSI) at discriminating between normal controls and keratoconus suspects was assessed. RESULTS The TBI had the best discriminative ability with the greatest area under the receiver operating characteristic (AUROC) curve value of 0.946 for normal controls versus TBF eyes, and 0.824 for normal controls versus TNF eyes. Compared to the TBI AUROC curves, SP-A1 and CBI had AUROC curve values of 0.833 (P = .09) and 0.822 (P = .01) for normal controls versus TBF eyes, respectively, and AUROC curve values of 0.822 (P = .96) and 0.550 (P = .0002) for normal controls versus TNF eyes, respectively. The TBI had the best positive predictive value for TNF and TBF eyes, followed by CBI and SP-A1. CONCLUSIONS The TBI and the purely biomechanical parameter SP-A1 were of moderate utility in distinguishing between normal and keratoconus suspect eyes. In the absence of topographic/tomographic evidence of keratectasia, an independently abnormal biomechanical parameter may suggest an increased risk of ectasia. [J Refract Surg. 2022;38(5):318-325.].
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Yousefi A, Roberts CJ, Reilly MA. The Shape of Corneal Deformation Alters Air Puff–Induced Loading. Front Bioeng Biotechnol 2022; 10:848060. [PMID: 35433651 PMCID: PMC9006101 DOI: 10.3389/fbioe.2022.848060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 03/03/2022] [Indexed: 12/03/2022] Open
Abstract
Purpose: To determine the dynamic modification of the load exerted on the eye during air-puff testing by accounting for the deformation of the cornea. Methods: The effect of corneal load alteration with surface shape (CLASS) was characterized as an additional component of the load produced during the concave phase where the fluid outflow tangential to the corneal surface creates backward pressure. Concave phase duration (tCD), maximum CLASS value (CLASSmax), and the area under CLASS-time curve (CLASSint) are calculated for 26 keratoconic (KCN), 102 normal (NRL), and 29 ocular hypertensive (OHT) subjects. Tukey’s HSD tests were performed to compare the three subject groups. A p-value less than 0.05 was considered statistically significant. Results: Accounting for CLASS increased the load by 34.6% ± 7.7% at maximum concavity; these differences were greater in KCN subjects (p < 0.0001) and lower in OHT subjects (p = 0.0028) than in NRL subjects. tCD and CLASSint were significantly longer and larger, respectively, for KCN subjects than those in the NRL and OHT groups (p < 0.0001). Conclusion: Load characterization is an essential step in assessing the cornea’s biomechanical response to air-puff–induced deformation. The dynamic changes in the corneal surface shape significantly alter the load experienced by the corneal apex. This implies a subject-specific loading dynamic even if the air puff itself is identical. This is important when comparing the same eye after a surgical procedure or topical medication that alters corneal properties. Stiffer corneas are least sensitive to a change in load, while more compliant corneas show higher sensitivity.
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Affiliation(s)
- Atieh Yousefi
- Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, United States
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
| | - Cynthia J. Roberts
- Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, United States
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
- *Correspondence: Cynthia J. Roberts,
| | - Matthew A. Reilly
- Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, United States
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
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Abstract
Purpose The purpose of this study was to investigate the mechanism of potential droplet formation in response to air puff deformation with two noncontact tonometers (NCTs). Methods Twenty healthy volunteers were examined using two NCTs, Ocular Response Analyzer and Corvis ST, and two contact tonometers, iCare and Tono-Pen. High-speed videos of the tear film response were captured with at spatial resolution of 20 microns/pixel at 2400 fps. Droplet size, droplet velocity, distance between air puff impact location, and the tear meniscus-lid margin were characterized. Results One subject was excluded due to technical issues. Droplets were detected only in tests with instilled eye drop. Videos showed the tear film rolls away from the apex while remaining adherent to the ocular surface due to the tendency of the fluid to remain attached to a solid surface explained by the Coanda effect. Twelve out of 38 videos with an eye drop administration showed droplet formation. Only one resulted in droplets with predominantly forward motion, which had the shortest distance between air puff impact location and lower meniscus. This distance on average was 5.9 ± 1.1 mm. The average droplet size was 500 ± 200 µm. Conclusions Results indicate no droplet formation under typical clinical setting. Hence, standard clinical use of NCT tests is not expected to cause droplets. NCT testing with eye drop administration showed droplet formation at the inferior eyelid boundary, which acts as a barrier and interrupts tear flow. Translational Relevance Study of tear film interaction with NCT air puff shows that these tonometers are not expected to cause droplet formation in standard use and that if external drops are required, both eyelids should be held if patients need assistance to maintain open eyes to avoid droplets with predominantly forward motion.
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Affiliation(s)
- Atieh Yousefi
- Department of Ophthalmology & Visual Sciences, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Yanhui Ma
- Department of Ophthalmology & Visual Sciences, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Cynthia J Roberts
- Department of Ophthalmology & Visual Sciences, The Ohio State University College of Medicine, Columbus, OH, USA.,Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Sayoko E Moroi
- Department of Ophthalmology & Visual Sciences, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Matthew A Reilly
- Department of Ophthalmology & Visual Sciences, The Ohio State University College of Medicine, Columbus, OH, USA.,Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
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Ma Y, Ohr MP, Pan X, Roberts CJ. Quantifying the pattern of retinal vascular orientation in diabetic retinopathy using optical coherence tomography angiography. Sci Rep 2021; 11:15826. [PMID: 34349166 PMCID: PMC8338926 DOI: 10.1038/s41598-021-95219-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Accepted: 07/22/2021] [Indexed: 12/24/2022] Open
Abstract
Quantitative imaging using optical coherence tomography angiography (OCTA) could provide objective tools for the detection and characterization of diabetic retinopathy (DR). In this study, an operator combining the second derivative and Gaussian multiscale convolution is applied to identify the retinal orientation at each pixel in the OCTA image. We quantified the pattern of retinal vascular orientation and developed three novel quantitative metrics including vessel preferred orientation, vessel anisotropy, and vessel area. Each of eight 45º sectors of the circular disk centered at the macular region was defined as the region of interest. Significant sectoral differences were observed in the preferred orientation (p < 0.0001) and vessel area (p < 0.0001) in the 34 healthy subjects, whereas vessel anisotropy did not demonstrate a significant difference among the eight sectors (p = 0.054). Differential retinal microvascular orientation patterns were observed between healthy controls (n = 34) and the DR subjects (n = 7). The vessel area characterized from the vascular orientation pattern was shown to be strongly correlated with the traditionally reported vessel density (Pearson R > 0.97, p < 0.0001). With three metrics calculated from the vascular orientation pattern simultaneously and sectorally, our quantitative assessment for retinal microvasculature provides more information than vessel density alone and thereby may enhance the detection of DR. These preliminary results suggest the feasibility and advantage of our vessel orientation-based quantitative approach using OCTA to characterize DR-associated changes in retinal microvasculature.
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Affiliation(s)
- Yanhui Ma
- Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA.
| | - Matthew P Ohr
- Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA
| | - Xueliang Pan
- Department of Biomedical Informatics, The Ohio State University, Columbus, OH, USA
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA.,Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
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20
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Jun I, Kang DSY, Roberts CJ, Lee H, Jean SK, Kim EK, Seo KY, Kim TI. Comparison of Clinical and Biomechanical Outcomes of Small Incision Lenticule Extraction With 120- and 140-µm Cap Thickness. Transl Vis Sci Technol 2021; 10:15. [PMID: 34259803 PMCID: PMC8288062 DOI: 10.1167/tvst.10.8.15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The purpose of this study was to compare the clinical outcomes and corneal biomechanical changes between 120-µm and 140-µm cap thickness after small incision lenticule extraction (SMILE). Methods This prospective study included 150 eyes (150 patients: 91 eyes in the 120-µm group, and 59 eyes in the 140-µm group) who underwent SMILE. Enhanced correction nomograms were applied for patients according to cap thickness. Clinical outcomes, including visual acuity, refraction, and corneal wavefront aberrations, were compared between the two groups. Corneal biomechanics were evaluated using the Corvis ST (Oculus, Wetzlar, Germany). Results The mean uncorrected-distance visual acuity, safety and efficacy indices, and refractive predictability were comparable in the 120-µm and 140-µm groups after SMILE. The postoperative total corneal root mean square higher-order aberrations (HOAs) and spherical aberrations was 0.48 ± 0.31 and 0.26 ± 0.10 in the 120-µm group, and 0.53 ± 0.16 and 0.34 ± 0.13 in the 140-µm group, which showed significant differences between the two groups (P = 0.027, and <0.001, respectively). Although corneal stiffness decreased after SMILE in both groups, the changes in the deformation amplitude ratio were significantly higher in the 140-µm group than in the 120-µm group (P = 0.022). Conclusions SMILE with 120-µm and 140-µm cap thickness provided excellent predictable outcomes according to our enhanced correction nomogram. The amount of tissue removal required to achieve the same amount of refractive correction was greater in the thicker cap group. The induction of corneal HOAs and weakening of corneal biomechanics were less pronounced in the thin-cap group, which may be associated with the thinner cap, lesser lenticule thickness, or thicker residual stromal bed. Translational Relevance Although SMILE with different cap thickness was effective, thicker lenticule thickness in the thick-cap group may be associated with induction of HOAs, and corneal stiffness changes.
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Affiliation(s)
- Ikhyun Jun
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Republic of Korea.,Corneal Dystrophy Research Institute, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Republic of Korea
| | | | - Cynthia J Roberts
- Department of Ophthalmology & Visual Sciences and Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Hun Lee
- Department of Ophthalmology, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | | | - Eung Kweon Kim
- Corneal Dystrophy Research Institute, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Republic of Korea.,Saevit Eye Hospital, Goyang-Si, Gyeonggi-Do, Republic of Korea
| | - Kyoung Yul Seo
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Tae-Im Kim
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Republic of Korea.,Corneal Dystrophy Research Institute, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Republic of Korea
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21
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Ma Y, Moroi SE, Roberts CJ. Non-invasive Clinical Measurement of Ocular Rigidity and Comparison to Biomechanical and Morphological Parameters in Glaucomatous and Healthy Subjects. Front Med (Lausanne) 2021; 8:701997. [PMID: 34291068 PMCID: PMC8287026 DOI: 10.3389/fmed.2021.701997] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/07/2021] [Indexed: 11/13/2022] Open
Abstract
Purpose: To assess ocular rigidity using dynamic optical coherence tomography (OCT) videos in glaucomatous and healthy subjects, and to evaluate how ocular rigidity correlates with biomechanical and morphological characteristics of the human eye. Methods: Ocular rigidity was calculated using Friedenwald's empirical equation which estimates the change in intraocular pressure (IOP) produced by volumetric changes of the eye due to choroidal pulsations with each heartbeat. High-speed OCT video was utilized to non-invasively measure changes in choroidal volume through time-series analysis. A control-case study design was based on 23 healthy controls and 6 glaucoma cases. Multiple diagnostic modalities were performed during the same visit including Spectralis OCT for nerve head video, Pascal Dynamic Contour Tonometry for IOP and ocular pulse amplitude (OPA) measurement, Corvis ST for measuring dynamic biomechanical response, and Pentacam for morphological characterization. Results: Combining glaucoma and healthy cohorts (n = 29), there were negative correlations between ocular rigidity and axial length (Pearson R = −0.53, p = 0.003), and between ocular rigidity and anterior chamber volume (R = −0.64, p = 0.0002). There was a stronger positive correlation of ocular rigidity and scleral stiffness (i.e., stiffness parameter at the highest concavity [SP-HC]) (R = 0.62, p = 0.0005) compared to ocular rigidity and corneal stiffness (i.e., stiffness parameter at the first applanation [SP-A1]) (R = 0.41, p = 0.033). In addition, there was a positive correlation between ocular rigidity and the static pressure-volume ratio (P/V ratio) (R = 0.72, p < 0.0001). Conclusions: Ocular rigidity was non-invasively assessed using OCT video and OPA in a clinic setting. The significant correlation of ocular rigidity with biomechanical parameters, SP-HC and P/V ratio, demonstrated the validity of the ocular rigidity measurement. Ocular rigidity is driven to a greater extent by scleral stiffness than corneal stiffness. These in vivo methods offer an important approach to investigate the role of ocular biomechanics in glaucoma.
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Affiliation(s)
- Yanhui Ma
- Department of Ophthalmology and Visual Sciences, The Ohio State University Wexner Medical Center, Columbus, OH, United States
| | - Sayoko E Moroi
- Department of Ophthalmology and Visual Sciences, The Ohio State University Wexner Medical Center, Columbus, OH, United States
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Sciences, The Ohio State University Wexner Medical Center, Columbus, OH, United States.,Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
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22
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Okon MD, Ma Y, Liu J, Roberts CJ. Changes in Central Corneal Thickness With Air-Puff-Induced Corneal Deformation Using a Method to Correct Scheimpflug and Refractive Distortion. J Refract Surg 2021; 37:422-428. [PMID: 34170774 DOI: 10.3928/1081597x-20210219-01] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To establish a method to determine central corneal thickness (CCT) and anterior chamber depth (ACD) of an air-puff-deformed cornea at the highest concavity (HC) state. METHODS The Fink method for refractive correction of Scheimpflug images of a convex pre-deformed (PRE) cornea was implemented for 155 eyes of 155 participants imaged with the Corvis ST (Oculus Optikgeräte GmbH). This method was subsequently modified for the HC state of deformation. The tracked edges of each participant's cornea were exported at the PRE and HC states. Ten participants who had a visible crystalline lens in the image were selected to determine ACD in both states. The center points on the corneal tracked edges and lens were used to determine uncorrected CCT and ACD, respectively. RESULTS Average undeformed CCTPRE was significantly lower than deformed CCTHC (584 ± 31 and 626 ± 34 µm, respectively) (P < .0001). No significant difference was found for the corrected ACD between the two states. Corrected CCT and ACD were significantly greater than the corresponding uncorrected values for both deformation states (P < .0001). Percent change in CCT was found to be correlated to change in arc length at HC (P < .0001). CONCLUSIONS Distortion in Corvis ST images at the HC state can be corrected using a modified Fink method. CCT was found to increase in the HC state, compared to the PRE state. The CCT change during deformation may be important in the study of the compressive response of the cornea. [J Refract Surg. 2021;37(6):422-428.].
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24
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Scott JA, Roberts CJ, Mahmoud AM, Jain SG. Evaluating the Relationship of Intraocular Pressure and Anterior Chamber Volume With Use of Prostaglandin Analogues. J Glaucoma 2021; 30:421-427. [PMID: 33149104 DOI: 10.1097/ijg.0000000000001736] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 10/24/2020] [Indexed: 11/26/2022]
Abstract
PRCIS In this prospective study, naive prostaglandin use in primary open-angle glaucoma was associated with scleral biomechanical alteration and intraocular pressure (IOP) measuring errors. PURPOSE The purpose of this study is to determine the effects of naïve use of prostaglandin analogues (PGA) on IOP and anterior chamber volume (ACV), as well as investigate how PGAs might affect corneal and scleral stiffness and their impact on ocular rigidity. MATERIALS AND METHODS This study was a prospective study of 21 recently diagnosed open-angle glaucoma patients (33 eyes) initiating medical therapy with a topical prostaglandin eye drop. Corneal morphologic and biomechanical parameters as well as IOP were measured at 3 visits over a 4-month period with the following equipment: Pentacam, Corvis ST, Ocular Response Analyzer, Goldmann applanation tonometry (GAT) and Pascal dynamic contour tonometry. RESULTS The study demonstrated a significant decrease in mean IOP with initiation of PGA in all 4 tonometers (P<0.0001). The greatest change in IOP occurred in the first 4 weeks of treatment (P<0.0001). The mean ACV showed a significant decrease at visit 2 (P<0.02) and visit 3 (P<0.04) compared with baseline visit 1. However, there was a paradoxical increase in ACV in 37% of eyes at visit 2, despite a significant mean reduction in IOP by GAT and dynamic contour tonometry.The IOP/ACV ratio at visit 1 significantly predicted the reduction in respective measures of IOP, as well as scleral stiffness measured by stiffness parameter-highest concavity. CONCLUSION In clinical practice, GAT may not be the most appropriate tonometer for measuring IOP in PGA treated eyes due the measurement errors from ocular biomechanical alteration. The IOP/ACV ratio could potentially serve as a new diagnostic parameter to determine the likelihood of PGA treatment success.
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Affiliation(s)
| | - Cynthia J Roberts
- Departments of Ophthalmology & Vision Sciences
- Biomedical Engineering, Havener Eye Institute, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Ashraf M Mahmoud
- Departments of Ophthalmology & Vision Sciences
- Biomedical Engineering, Havener Eye Institute, The Ohio State University Wexner Medical Center, Columbus, OH
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25
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Zhang H, Eliasy A, Lopes B, Abass A, Vinciguerra R, Vinciguerra P, Ambrósio R, Roberts CJ, Elsheikh A. Stress-Strain Index Map: A New Way to Represent Corneal Material Stiffness. Front Bioeng Biotechnol 2021; 9:640434. [PMID: 33777912 PMCID: PMC7991572 DOI: 10.3389/fbioe.2021.640434] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 02/11/2021] [Indexed: 11/23/2022] Open
Abstract
Purpose To introduce a new method to map the mechanical stiffness of healthy and keratoconic corneas. Methods Numerical modeling based on the finite element method was used to carry out inverse analysis of simulated healthy and keratoconic corneas to determine the regional variation of mechanical stiffness across the corneal surface based on established trends in collagen fibril distribution. The Stress–Strain Index (SSI), developed and validated in an earlier study and presented as a parameter that can estimate the overall stress–strain behavior of corneal tissue, was adopted in this research as a measure of corneal stiffness. The regional variation of SSI across the corneal surface was estimated using inverse analysis while referring to the common features of collagen fibrils’ distribution obtained from earlier x-ray scattering studies. Additionally, for keratoconic corneas, a method relating keratoconic cone features and cornea’s refractive power to the reduction in collagen fibril density inside the cone was implemented in the development of SSI maps. In addition to the simulated cases, the study also included two keratoconus cases, for which SSI maps were developed. Results SSI values varied slightly across corneal surface in the simulated healthy eyes. In contrast, both simulated and clinical keratoconic corneas demonstrated substantial reductions in SSI values inside the cone. These SSI reductions depended on the extent of the disease and increased with more considerable simulated losses in fibril density in the cone area. SSI values and their regional variation showed little change with changes in IOP, corneal thickness, and curvature. Conclusion SSI maps provide an estimation of the regional variation of biomechanical stiffness across the corneal surface. The maps could be particularly useful in keratoconic corneas, demonstrating the dependence of corneal biomechanical behavior on the tissue’s microstructure and offering a tool to fundamentally understand the mechanics of keratoconus progression in individual patients.
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Affiliation(s)
- Haixia Zhang
- School of Engineering, University of Liverpool, Liverpool, United Kingdom.,School of Biomedical Engineering, Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, China
| | - Ashkan Eliasy
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Bernardo Lopes
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Ahmed Abass
- Department of Mechanical, Materials and Aerospace Engineering, School of Engineering, University of Liverpool, Liverpool, United Kingdom.,Department of Production Engineering and Mechanical Design, Faculty of Engineering, Port Said University, Port Fouad, Egypt
| | - Riccardo Vinciguerra
- Department of Ophthalmology, Humanitas San Pio X Hospital, Milan, Italy.,The School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Paolo Vinciguerra
- Humanitas Clinical and Research Center, IRCCS, Rozzano, Italy.,Department of Biomedical Sciences, Humanitas University, Milan, Italy
| | - Renato Ambrósio
- Department of Ophthalmology, Federal University of São Paulo (UNIFESP), São Paulo, Brazil.,Department of Ophthalmology, Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, Brazil
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Sciences and Biomedical Engineering, The Ohio State University, Columbus, OH, United States
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, United Kingdom.,Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, China.,NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust, UCL Institute of Ophthalmology, London, United Kingdom
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Pappa CS, Nguyen BA, Mahmoud AM, Agarwal G, Roberts CJ. Effect of penetration enhancer with novel corneal cross-linking using recombinant human decoron in porcine eyes. Exp Eye Res 2021; 206:108542. [PMID: 33744258 DOI: 10.1016/j.exer.2021.108542] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 02/15/2021] [Accepted: 03/10/2021] [Indexed: 11/19/2022]
Abstract
The aim of the study was to investigate the effectiveness of exogenous recombinant human decoron and an accompanying penetration-enhancing solution in stiffening ex-vivo porcine corneas both transepithelially and after de-epithelialization. Eight porcine paired eyes were treated transepithelially: one eye with a pre-treatment solution (Pre-Tx), penetration enhancing solution (PE), and decoron while the fellow eye was treated by the same protocol but without decoron. A second group included 4 de-epithelialized pairs treated identically. The final group included 4 de-epithelialized pairs with one eye treated with Pre-Tx, PE, and decoron while the fellow eye was treated without PE. Uniaxial tensile testing was used to compare the corneal stiffness between the different treatment conditions. Residual tissue underwent immunohistochemistry analysis to evaluate the depth of penetration of decoron into the corneal stroma. There was no stiffening effect exhibited among corneas treated transepithelially with decoron compared to control (P > 0.05) and poor stromal penetration was exhibited on tissue analysis. Among de-epithelialized corneas, there was a significant stiffening effect seen in those treated with decoron at 3%, 4%, 5%, & 6% strain (P < 0.05) compared to control. Among de-epithelialized corneas there was also a significant stiffening effect seen in those treated with the PE and decoron at 4%, 5%, & 6% strain (P < 0.05) with improved stromal penetration confirmed by immunohistochemistry, versus without PE. De-epithelialization is necessary for effective stromal penetration of decoron. Depth of penetration and subsequent corneal stiffening may be improved with a penetration enhancing solution. Compared to riboflavin, decoron requires shorter treatment time and spares UV light exposure.
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Affiliation(s)
- Christopher S Pappa
- Department of Ophthalmology & Visual Sciences, William H. Havener Eye Institute, 915 Olentangy River Rd, Suite 5000, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - B Audrey Nguyen
- Department of Biomedical Engineering, 140 W. 19th Ave., Fontana Labs the Ohio State University, Columbus, OH, USA
| | - Ashraf M Mahmoud
- Department of Ophthalmology & Visual Sciences, William H. Havener Eye Institute, 915 Olentangy River Rd, Suite 5000, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Biomedical Engineering, 140 W. 19th Ave., Fontana Labs the Ohio State University, Columbus, OH, USA
| | - Gunjan Agarwal
- Department of Ophthalmology & Visual Sciences, William H. Havener Eye Institute, 915 Olentangy River Rd, Suite 5000, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Cynthia J Roberts
- Department of Ophthalmology & Visual Sciences, William H. Havener Eye Institute, 915 Olentangy River Rd, Suite 5000, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Biomedical Engineering, 140 W. 19th Ave., Fontana Labs the Ohio State University, Columbus, OH, USA.
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Sedaghat MR, Momeni-Moghaddam H, Azimi A, Fakhimi Z, Ziaei M, Danesh Z, Roberts CJ, Monfared N, Jamali A. Corneal Biomechanical Properties in Varying Severities of Myopia. Front Bioeng Biotechnol 2021; 8:595330. [PMID: 33553113 PMCID: PMC7859342 DOI: 10.3389/fbioe.2020.595330] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 12/21/2020] [Indexed: 11/20/2022] Open
Abstract
Purpose: To investigate corneal biomechanical response parameters in varying degrees of myopia and their correlation with corneal geometrical parameters and axial length. Methods: In this prospective cross-sectional study, 172 eyes of 172 subjects, the severity degree of myopia was categorized into mild, moderate, severe, and extreme myopia. Cycloplegic refraction, corneal tomography using Pentacam HR, corneal biomechanical assessment using Corvis ST and Ocular Response Analyser (ORA), and ocular biometry using IOLMaster 700 were performed for all subjects. A general linear model was used to compare biomechanical parameters in various degrees of myopia, while central corneal thickness (CCT) and biomechanically corrected intraocular pressure (bIOP) were considered as covariates. Multiple linear regression was used to investigate the relationship between corneal biomechanical parameters with spherical equivalent (SE), axial length (AXL), bIOP, mean keratometry (Mean KR), and CCT. Results: Corneal biomechanical parameters assessed by Corvis ST that showed significant differences among the groups were second applanation length (AL2, p = 0.035), highest concavity radius (HCR, p < 0.001), deformation amplitude (DA, p < 0.001), peak distance (PD, p = 0.022), integrated inverse radius (IR, p < 0.001) and DA ratio (DAR, p = 0.004), while there were no significant differences in the means of pressure-derived parameters of ORA between groups. Multiple regression analysis showed all parameters of Corvis ST have significant relationships with level of myopia (SE, AXL, Mean KR), except AL1 and AL2. Significant biomechanical parameters showed progressive reduction in corneal stiffness with increasing myopia (either with greater negative SE or greater AXL), independent of IOP and CCT. Also, corneal hysteresis (CH) or ability to dissipate energy from the ORA decreased with increasing level of myopia. Conclusions: Dynamic corneal response assessed by Corvis ST shows evidence of biomechanical changes consistent with decreasing stiffness with increasing levels of myopia in multiple parameters. The strongest correlations were with highest concavity parameters where the sclera influence is maximal.
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Affiliation(s)
| | | | - Abbas Azimi
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.,Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Zohreh Fakhimi
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mohammed Ziaei
- Department of Ophthalmology, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
| | - Zeynad Danesh
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Cynthia J Roberts
- Ophthalmology & Visual Science, Biomedical Engineering, The Ohio State University, Columbus, OH, United States
| | - Naeemeh Monfared
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Alireza Jamali
- Department of Optometry, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran
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Hashemi H, Amanzadeh K, Seyedian M, Zeraati H, Roberts CJ, Mehravaran S, Ambrósio R, Vinciguerra R, Vinciguerra P, Asgari S. Accelerated and Standard Corneal Cross-Linking Protocols in Patients with Down Syndrome: A Non-inferiority Contralateral Randomized Trial. Ophthalmol Ther 2020; 9:1011-1021. [PMID: 33006120 PMCID: PMC7708533 DOI: 10.1007/s40123-020-00303-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 09/10/2020] [Indexed: 11/28/2022] Open
Abstract
Introduction To compare the results of an accelerated corneal cross-linking (CXL) protocol (9 mW/cm2, 10 min) with the standard CXL protocol (3 mW/cm2, 30 min) in patients with Down syndrome (DS) who have keratoconus (KC). Methods Twenty-seven 10- to 20-year-old patients with DS who had bilateral progressive KC were enrolled in a contralateral randomized trial and completed 2 years of follow-up examinations. Fellow eyes were randomly allocated to the accelerated CXL group or the standard CXL group. The main outcome measure was change in maximum keratometry (Kmax) centered on the steepest point (zonal Kmax − 3 mm) with a non-inferiority margin of 1.0 diopter (D). Vision and refraction tests, ophthalmic examinations, and corneal tomography were performed at baseline and at 6, 12, and 24 months after CXL. Failure was defined as an increase of ≥ 1.0 D in zonal Kmax − 3 mm within a 12-month period. Results The mean age (± standard deviation) of the patients was 15.71 ± 2.40 years. The within-group change in zonal Kmax − 3 mm was not significant after 2 years in either group, and within-group zonal Kmax − 3 mm remained stable. At 2 years after CXL, the mean change in the zonal Kmax − 3 mm was – 0.02 ± 0.81 D and – 0.31 ± 0.86 D in the accelerated CXL and standard CXL groups, respectively (P = 0.088). At 1 year of follow-up, three patients in the accelerated CXL group showed treatment failure (mean change in zonal Kmax − 3 mm + 2.12 ± 0.11 D); no patients in the standard CXL group showed treatment failure. At 2 years of follow-up, these three patients showed a decrease of – 0.43 ± 0.18 D in zonal Kmax − 3 mm from a baseline value of 55.11 ± 0.32 D. The 2-year trends of the inferior–superior asymmetry and vertical coma were statistically significantly different between the two groups, with the accelerated CXL protocol showing superiority in patients with higher baseline values. Conclusion In young patients with Down syndrome, the accelerated CXL protocol was able to halt disease progression and may be an alternative for the standard CXL protocol. In advanced KC, the efficacy of the accelerated approach was delayed and appeared later in the follow-up. In asymmetric cornea, the accelerated CXL resulted in centralization of the corneal cone. Trial Registration Iranian Registry of Clinical Trials, IRCT20100706004333N3 Electronic supplementary material The online version of this article (10.1007/s40123-020-00303-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Hassan Hashemi
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
| | - Kazem Amanzadeh
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
| | - Mohammad Seyedian
- Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran
| | - Hojjat Zeraati
- Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Science, The Ohio State University, Columbus, OH, USA.,Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Shiva Mehravaran
- ASCEND Center for Biomedical Research, Morgan State University, Baltimore, MD, USA
| | - Renato Ambrósio
- Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, RJ, Brazil.,Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, Brazil
| | | | - Paolo Vinciguerra
- Department of Biomedical Sciences, Humanitas University, Pieve Emanuele, Milan, Italy.,Humanitas Clinical and Research, Rozzano, Italy
| | - Soheila Asgari
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
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Taroni L, Bernabei F, Pellegrini M, Roda M, Toschi PG, Mahmoud AM, Schiavi C, Giannaccare G, Roberts CJ. Corneal Biomechanical Response Alteration After Scleral Buckling Surgery for Rhegmatogenous Retinal Detachment. Am J Ophthalmol 2020; 217:49-54. [PMID: 32283097 DOI: 10.1016/j.ajo.2020.03.054] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/25/2020] [Accepted: 03/31/2020] [Indexed: 12/17/2022]
Abstract
PURPOSE To compare the corneal biomechanics of eyes that underwent scleral buckle (SB) for rhegmatogenous retinal detachment (RRD) with those of fellow eyes (fellow eyes) and to further investigate the effects of SB on intraocular pressure (IOP) values. DESIGN Retrospective, fellow-eye matched cohort study. METHODS A total of 18 consecutive patients (11 males and 7 females) treated with SB for RRD in 1 eye were enrolled. Goldmann applanation tonometry was used to measure IOP. Biomechanical properties of the cornea were investigated by using the Ocular Response Analyzer (ORA) (Reichert Instruments) for the calculation of corneal resistant factor (CRF), corneal hysteresis, Goldmann-correlated IOP, and corneal-compensated IOP. Customized software was used for analysis of the ORA infrared and pressure signals, and a significance threshold was set to a P value of .05. RESULTS Operated eyes (OEs) showed significantly lower values of corneal hysteresis and CRF than fellow eyes (9.0 ± 1.8 vs 10.1 ± 1.8 mm Hg, respectively; P < .001; 10.0 ± 2.2 vs 10.9 ± 2.2 mm Hg; P < .001). GAT was significantly lower than corneal-compensated IOP in OEs (18.1 ± 4.9 vs 19.8 ± 4.8 mm Hg, respectively; P = .022) but not in fellow eyes. The second applanation event (A2) took place earlier in time, and the cornea was moving faster during A2 in the OEs than in the fellow eyes. CONCLUSIONS SB for the treatment of RRD affects corneal biomechanical response, likely due to a less compliant sclera that limits corneal motion and reduces energy dissipation, reflected in a lower corneal hysteresis. This has potentially meaningful clinical implications as the accuracy of the measurement of IOP values may be affected in these eyes.
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Affiliation(s)
- Leonardo Taroni
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy.
| | - Federico Bernabei
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy
| | - Marco Pellegrini
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy
| | - Matilde Roda
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy
| | - Pier Giorgio Toschi
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy
| | - Ashraf M Mahmoud
- Department of Ophthalmology and Visual Science and Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA
| | - Costantino Schiavi
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy
| | - Giuseppe Giannaccare
- Department of Ophthalmology, S.Orsola-Malpighi University Hospital, University of Bologna, Bologna, Italy; Department of Ophthalmology, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Science and Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA
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Eliasy A, Abass A, Lopes BT, Vinciguerra R, Zhang H, Vinciguerra P, Ambrósio R, Roberts CJ, Elsheikh A. Characterization of cone size and centre in keratoconic corneas. J R Soc Interface 2020; 17:20200271. [PMID: 32752996 DOI: 10.1098/rsif.2020.0271] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
A novel method to locate the centre of keratoconus (KC) and the transition zone between the pathological area and the rest of the corneal tissue is proposed in this study. A spherical coordinate system was used to generate a spherical height map measured relative to the centre of the optimal sphere fit, and normal to the surface. The cone centre was defined as the point with the maximum height. Second derivatives of spherical height were then used to estimate the area of pathology in an iterative process. There was mirror symmetry between cone centre locations in both eyes. The mean distance between cone centre and corneal apex was 1.45 ± 0.25 mm (0.07-2.00), the mean cone height normal to the surface was 37 ± 23 µm (2-129) and 75 ± 45 µm (5-243) in the anterior and posterior surfaces, respectively. There was a significant negative correlation between the cone height and the radius of the sphere of optimal fit (p < 0.05 for both anterior and posterior surfaces). On average, posterior cone height was larger than the corresponding anterior cone height by 37 ± 24 µm (0-158). The novel method proposed can be used to estimate the cone centre and area, and explore the changes in anterior and posterior corneal surfaces that take place with KC progression. It can help improve understanding of keratoconic corneal morphology and assist in developing customized treatments.
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Affiliation(s)
- Ashkan Eliasy
- School of Engineering, University of Liverpool, Liverpool, UK
| | - Ahmed Abass
- School of Engineering, University of Liverpool, Liverpool, UK
| | - Bernardo T Lopes
- School of Engineering, University of Liverpool, Liverpool, UK.,Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, Brazil.,Department of Ophthalmology, Federal University of Sao Paulo (UNIFESP), Sao Paulo, Brazil
| | | | - Haixia Zhang
- School of Biomedical Engineering, Capital Medical University, Beijing, People's Republic of China
| | - Paolo Vinciguerra
- Department of Biomedical Science, Humanitas University, Via Manzoni 56, Rozzano, Milan, Italy.,Eye Center, Humanitas Clinical and Research Center, Via Manzoni 56, Rozzano, Milan, Italy
| | - Renato Ambrósio
- Department of Ophthalmology, Federal University of Sao Paulo (UNIFESP), Sao Paulo, Brazil.,Department of Ophthalmology, Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, Brazil
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Science and Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, UK.,Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, People's Republic of China.,NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
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Abass A, Roberts CJ, Lopes B, Eliasy A, Vinciguerra R, Ambrósio R, Vinciguerra P, Elsheikh A. Can the Corvis ST Estimate Corneal Viscoelasticity? J Refract Surg 2020; 36:346-347. [PMID: 32396647 DOI: 10.3928/1081597x-20200212-04] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Nguyen BA, Reilly MA, Roberts CJ. Biomechanical contribution of the sclera to dynamic corneal response in air-puff induced deformation in human donor eyes. Exp Eye Res 2019; 191:107904. [PMID: 31883460 DOI: 10.1016/j.exer.2019.107904] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 12/18/2019] [Accepted: 12/24/2019] [Indexed: 02/01/2023]
Abstract
This study was conducted to evaluate the impact of varying scleral material properties on the biomechanical response of the cornea under air-puff induced deformation. Twenty pairs of human donor eyes were obtained for this study. One eye from each pair had its sclera stiffened using 4% glutaraldehyde, while the fellow eye served as control for uniaxial strip testing. The whole globes were mounted in a rigid holder and intraocular pressure (IOP) was set using a saline column. Dynamic corneal response parameters were measured before and after scleral stiffening using the CorVis ST, a dynamic Scheimpflug analyzer. IOP was set to 10, 20, 30, and 40 mmHg, with at least 3 examinations performed at each pressure step. Uniaxial tensile testing data were fit to a neo-Hookean model to estimate the Young's modulus of treated and untreated sclera. Scleral Young's modulus was found to be significantly correlated with several response parameters, including Highest Concavity Deformation Amplitude, Peak Distance, Highest Concavity Radius, and Stiffness Parameter-Highest Concavity (SP-HC). There were significant increases in SP-HC after scleral stiffening at multiple levels of IOP, while no significant difference was observed in the corneal Stiffness Parameter - Applanation 1 (SP-A1) at any level of IOP. Scleral mechanical properties significantly influenced the corneal deformation response to an air-puff. The stiffer the sclera, the greater the constraining effect on corneal deformation resulting in lower displaced amplitude. This may have important clinical implications and suggests that both corneal and scleral material properties contribute to the observed corneal response in air-puff induced deformation.
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Affiliation(s)
- B Audrey Nguyen
- Department of Biomedical Engineering, 1080 Carmack Rd, 270 Bevis Hall, The Ohio State University, Columbus, OH, USA
| | - Matthew A Reilly
- Department of Biomedical Engineering, 1080 Carmack Rd, 270 Bevis Hall, The Ohio State University, Columbus, OH, USA; Department of Ophthalmology & Visual Science, William H. Havener Eye Institute, 915 Olentangy River Rd, Suite, 5000, The Ohio State University, Columbus, OH, USA
| | - Cynthia J Roberts
- Department of Biomedical Engineering, 1080 Carmack Rd, 270 Bevis Hall, The Ohio State University, Columbus, OH, USA; Department of Ophthalmology & Visual Science, William H. Havener Eye Institute, 915 Olentangy River Rd, Suite, 5000, The Ohio State University, Columbus, OH, USA.
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Lee H, Roberts CJ, Ambrósio R, Elsheikh A, Kang DSY, Kim TI. Effect of accelerated corneal crosslinking combined with transepithelial photorefractive keratectomy on dynamic corneal response parameters and biomechanically corrected intraocular pressure measured with a dynamic Scheimpflug analyzer in healthy myopic patients. J Cataract Refract Surg 2019; 43:937-945. [PMID: 28823441 DOI: 10.1016/j.jcrs.2017.04.036] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Revised: 04/12/2017] [Accepted: 04/12/2017] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate the effect of accelerated corneal crosslinking (CXL) combined with transepithelial photorefractive keratectomy (PRK) on changes in new dynamic corneal response parameters and the biomechanically corrected intraocular pressure (IOP) measured using a dynamic Scheimpflug analyzer (Corvis ST). SETTING Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, South Korea. DESIGN Retrospective case series. METHODS Medical records of eyes of healthy myopic patients having transepithelial PRK or transepithelial PRK with CXL were examined. Main outcome variables were the biomechanically corrected IOP and new dynamic corneal response parameters including the deformation amplitude ratio at 1.0 mm (DAR1) and at 2.0 mm (DAR2), stiffness at first applanation and at highest concavity, and the integrated inverse radius preoperatively and 6 months postoperatively. RESULTS The study comprised 69 eyes (69 patients); 35 had transepithelial PRK and 34, transepithelial PRK with CXL. The DAR1, DAR2, and integrated inverse radius significantly increased, while stiffness at first applanation and at highest concavity decreased postoperatively in both groups. Changes in the DAR2 and integrated inverse radius in the transepithelial PRK group were significantly larger than in the transepithelial PRK with CXL group without and with analysis of covariance with the spherical equivalent change or corneal thickness change as a covariate. No significant differences in the biomechanically corrected IOP occurred preoperatively or postoperatively in either group. CONCLUSIONS Results indicate that prophylactic CXL combined with transepithelial PRK has a role in reducing the change in corneal biomechanical properties. The dynamic Scheimpflug analyzer showed stable biomechanically corrected IOP measurements preoperatively and postoperatively.
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Affiliation(s)
- Hun Lee
- From the Department of Ophthalmology (Lee), International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, the Institute of Vision Research (Lee, Kim), Department of Ophthalmology, Yonsei University College of Medicine, and Eyereum Eye Clinic (Kang), Seoul, South Korea; the Department of Ophthalmology & Visual Science and Department of Biomedical Engineering (Roberts), Ohio State University, Columbus, Ohio, USA; the Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil; the School of Engineering (Elsheikh), University of Liverpool, Liverpool, United Kingdom
| | - Cynthia J Roberts
- From the Department of Ophthalmology (Lee), International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, the Institute of Vision Research (Lee, Kim), Department of Ophthalmology, Yonsei University College of Medicine, and Eyereum Eye Clinic (Kang), Seoul, South Korea; the Department of Ophthalmology & Visual Science and Department of Biomedical Engineering (Roberts), Ohio State University, Columbus, Ohio, USA; the Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil; the School of Engineering (Elsheikh), University of Liverpool, Liverpool, United Kingdom
| | - Renato Ambrósio
- From the Department of Ophthalmology (Lee), International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, the Institute of Vision Research (Lee, Kim), Department of Ophthalmology, Yonsei University College of Medicine, and Eyereum Eye Clinic (Kang), Seoul, South Korea; the Department of Ophthalmology & Visual Science and Department of Biomedical Engineering (Roberts), Ohio State University, Columbus, Ohio, USA; the Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil; the School of Engineering (Elsheikh), University of Liverpool, Liverpool, United Kingdom
| | - Ahmed Elsheikh
- From the Department of Ophthalmology (Lee), International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, the Institute of Vision Research (Lee, Kim), Department of Ophthalmology, Yonsei University College of Medicine, and Eyereum Eye Clinic (Kang), Seoul, South Korea; the Department of Ophthalmology & Visual Science and Department of Biomedical Engineering (Roberts), Ohio State University, Columbus, Ohio, USA; the Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil; the School of Engineering (Elsheikh), University of Liverpool, Liverpool, United Kingdom
| | - David Sung Yong Kang
- From the Department of Ophthalmology (Lee), International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, the Institute of Vision Research (Lee, Kim), Department of Ophthalmology, Yonsei University College of Medicine, and Eyereum Eye Clinic (Kang), Seoul, South Korea; the Department of Ophthalmology & Visual Science and Department of Biomedical Engineering (Roberts), Ohio State University, Columbus, Ohio, USA; the Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil; the School of Engineering (Elsheikh), University of Liverpool, Liverpool, United Kingdom
| | - Tae-Im Kim
- From the Department of Ophthalmology (Lee), International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, the Institute of Vision Research (Lee, Kim), Department of Ophthalmology, Yonsei University College of Medicine, and Eyereum Eye Clinic (Kang), Seoul, South Korea; the Department of Ophthalmology & Visual Science and Department of Biomedical Engineering (Roberts), Ohio State University, Columbus, Ohio, USA; the Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil; the School of Engineering (Elsheikh), University of Liverpool, Liverpool, United Kingdom.
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Lee H, Roberts CJ, Kim TI, Ambrósio R, Elsheikh A, Yong Kang DS. Changes in biomechanically corrected intraocular pressure and dynamic corneal response parameters before and after transepithelial photorefractive keratectomy and femtosecond laser-assisted laser in situ keratomileusis. J Cataract Refract Surg 2019; 43:1495-1503. [PMID: 29335093 DOI: 10.1016/j.jcrs.2017.08.019] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 08/25/2017] [Accepted: 08/28/2017] [Indexed: 11/16/2022]
Abstract
PURPOSE To evaluate the changes in biomechanically corrected intraocular pressure (IOP) and new dynamic corneal response parameters measured by a dynamic Scheimpflug analyzer before and after transepithelial photorefractive keratectomy (PRK) and femtosecond laser-assisted laser in situ keratomileusis (LASIK). SETTING Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, South Korea. DESIGN Retrospective case series. METHODS Medical records of patients having transepithelial PRK or femtosecond-assisted LASIK were examined. The primary outcome variables were biomechanically corrected IOP and dynamic corneal response parameters, including deformation amplitude ratio 2.0 mm, stiffness parameter at first applanation, Ambrósio relational thickness through the horizontal meridian, and integrated inverse radius before the procedure and 6 months postoperatively. RESULTS Of the 129 patients (129 eyes) in the study, 65 had transepithelial PRK and 64 had femtosecond-assisted LASIK. No significant differences in biomechanically corrected IOP were noted before and after surgery. The deformation amplitude ratio 2.0 mm and integrated inverse radius increased, whereas the stiffness parameter at first applanation and the Ambrósio relational thickness through the horizontal meridian decreased after surgery (P < .001). The changes in deformation amplitude ratio 2.0 mm and integrated inverse radius were smaller in transepithelial PRK than femtosecond-assisted LASIK (P < .001). Using analysis of covariance, with refractive error change or corneal thickness change as a covariate, the changes in deformation amplitude ratio 2.0 mm and integrated inverse radius were smaller in transepithelial PRK than femtosecond-assisted LASIK (P < .001). CONCLUSIONS The dynamic Scheimpflug analyzer showed stable biomechanically corrected IOP measurement before and after surgery. The changes in dynamic corneal response parameters were smaller with transepithelial PRK than with femtosecond-assisted LASIK, indicating less of a biomechanical effect with transepithelial PRK.
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Affiliation(s)
- Hun Lee
- From the Department of Ophthalmology (Lee), International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, the Eyereum Eye Clinic (Kang), Seoul, and the Institute of Vision Research (Lee, Kim), Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea; the Department of Ophthalmology & Visual Science and Department of Biomedical Engineering (Roberts), Ohio State University, Columbus, Ohio, USA; Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil; the School of Engineering (Elsheikh), University of Liverpool, Liverpool, United Kingdom
| | - Cynthia J Roberts
- From the Department of Ophthalmology (Lee), International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, the Eyereum Eye Clinic (Kang), Seoul, and the Institute of Vision Research (Lee, Kim), Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea; the Department of Ophthalmology & Visual Science and Department of Biomedical Engineering (Roberts), Ohio State University, Columbus, Ohio, USA; Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil; the School of Engineering (Elsheikh), University of Liverpool, Liverpool, United Kingdom
| | - Tae-Im Kim
- From the Department of Ophthalmology (Lee), International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, the Eyereum Eye Clinic (Kang), Seoul, and the Institute of Vision Research (Lee, Kim), Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea; the Department of Ophthalmology & Visual Science and Department of Biomedical Engineering (Roberts), Ohio State University, Columbus, Ohio, USA; Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil; the School of Engineering (Elsheikh), University of Liverpool, Liverpool, United Kingdom
| | - Renato Ambrósio
- From the Department of Ophthalmology (Lee), International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, the Eyereum Eye Clinic (Kang), Seoul, and the Institute of Vision Research (Lee, Kim), Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea; the Department of Ophthalmology & Visual Science and Department of Biomedical Engineering (Roberts), Ohio State University, Columbus, Ohio, USA; Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil; the School of Engineering (Elsheikh), University of Liverpool, Liverpool, United Kingdom
| | - Ahmed Elsheikh
- From the Department of Ophthalmology (Lee), International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, the Eyereum Eye Clinic (Kang), Seoul, and the Institute of Vision Research (Lee, Kim), Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea; the Department of Ophthalmology & Visual Science and Department of Biomedical Engineering (Roberts), Ohio State University, Columbus, Ohio, USA; Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil; the School of Engineering (Elsheikh), University of Liverpool, Liverpool, United Kingdom
| | - David Sung Yong Kang
- From the Department of Ophthalmology (Lee), International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, the Eyereum Eye Clinic (Kang), Seoul, and the Institute of Vision Research (Lee, Kim), Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea; the Department of Ophthalmology & Visual Science and Department of Biomedical Engineering (Roberts), Ohio State University, Columbus, Ohio, USA; Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil; the School of Engineering (Elsheikh), University of Liverpool, Liverpool, United Kingdom.
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Chen KJ, Eliasy A, Vinciguerra R, Abass A, Lopes BT, Vinciguerra P, Ambrósio R, Roberts CJ, Elsheikh A. Development and validation of a new intraocular pressure estimate for patients with soft corneas. J Cataract Refract Surg 2019; 45:1316-1323. [DOI: 10.1016/j.jcrs.2019.04.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 03/20/2019] [Accepted: 04/01/2019] [Indexed: 11/25/2022]
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Vinciguerra R, Ambrósio R, Roberts CJ, Elsheikh A, Lopes B, Vinciguerra P. Should the Corvis Biomechanical Index (CBI) Include Corneal Thickness Parameters? J Refract Surg 2019. [PMID: 29522232 DOI: 10.3928/1081597x-20180103-01] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Damgaard IB, Ang M, Mahmoud AM, Farook M, Roberts CJ, Mehta JS. Functional Optical Zone and Centration Following SMILE and LASIK: A Prospective, Randomized, Contralateral Eye Study. J Refract Surg 2019; 35:230-237. [PMID: 30984980 DOI: 10.3928/1081597x-20190313-01] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 03/13/2019] [Indexed: 11/20/2022]
Abstract
PURPOSE To compare centration and functional optical zone (FOZ) after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (LASIK). METHODS In this prospective, randomized, single-masked, paired-eyed, clinical trial, 70 patients received SMILE in one eye and LASIK in the other eye for myopia and myopic astigmatism. FOZ was calculated using custom software on 3-month postoperative refractive power maps (Pentacam HR; Oculus Optikgeräte GmbH, Wetzlar, Germany). Programmed treatment area was defined as the total area of the programmed OZ plus the transition zone. Centration was evaluated by the linear distance between FOZ centroid and the pupil center and the corneal apex. RESULTS The average preoperative spherical equivalent (-5.38 ± 1.65 vs -5.45 ± 1.61 diopters [D]), postoperative spherical equivalent (0.05 ± 0.39 vs 0.06 ± 0.39 D), uncorrected distance visual acuity (0.01 ± 0.13 vs 0.00 ± 0.08 logMAR), and corrected distance visual acuity (-0.07 ± 0.10 vs -0.07 ± 0.10 logMAR) were comparable in SMILE- and LASIK-treated eyes of the 60 patients with complete datasets (P > .419). Postoperative increase in spherical aberration was lower in SMILE than in LASIK (0.08 ± 0.16 vs 0.17 ± 0.18 µm, P = .002). The FOZ area was significantly larger in SMILE than in LASIK (30.25 ± 3.60 vs 29.21 ± 3.72 mm2), despite the smaller programmed OZ diameter (6.48 ± 0.08 vs 6.52 ± 0.11 mm) and smaller programmed treatment area (33.87 ± 0.81 vs 46.30 ± 2.61 mm2, P < .037). Pupil centration (0.43 ± 0.21 vs 0.41 ± 0.22 mm) and apex centration (0.48 ± 0.24 vs 0.48 ± 0.22 mm) were comparable between SMILE and LASIK (P > .694). CONCLUSIONS SMILE created a larger FOZ than LASIK, despite the smaller programmed OZ. This may be due to a difference in the biomechanical response between the two procedures. Visual outcome and centration were comparable between SMILE and LASIK. [J Refract Surg. 2019;35(4):230-237.].
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Lee H, Kang DSY, Reinstein DZ, Roberts CJ, Ambrósio R, Archer TJ, Jean SK, Kim EK, Seo KY, Jun I, Kim TI. Adjustment of Spherical Equivalent Correction According to Cap Thickness for Myopic Small Incision Lenticule Extraction. J Refract Surg 2019; 35:153-160. [PMID: 30855092 DOI: 10.3928/1081597x-20190205-01] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 02/05/2019] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate the amount of spherical equivalent correction for three different cap thicknesses (120, 130, and 140 µm) during myopic small incision lenticule extraction (SMILE) and determine the association between the amount of spherical equivalent correction and several variables in each cap thickness group. METHODS In this retrospective, comparative, observational case series study, the authors compared refractive errors, keratometric values, laser setting (sphere correction, cylinder correction, spherical equivalent correction, optical zone, and cap diameter), and spherical aberration measured preoperatively and at 3 months postoperatively between three different cap thickness groups: 120 µm (n = 554), 130 µm (n = 377), and 140 µm (n = 90). Multiple linear regression analyses were used to determine the associations between the amount of spherical equivalent correction and several variables, including age, preoperative spherical equivalent, optical zone diameter, central corneal thickness, preoperative mean keratometric values, and preoperative corneal asphericity. RESULTS According to cap thickness, attempted correction is adjusted to achieve the same refractive outcomes for different cap thicknesses. There were significant differences in the amount of sphere correction and spherical equivalent correction, as well as lenticule thickness, among subgroups. Changes in keratometric values, corneal asphericity, and spherical aberration were also significantly different among subgroups (all P < .001). Changes in keratometric values, corneal asphericity, and spherical aberration significantly increased as cap thickness increased. Preoperative spherical equivalent mainly influenced the amount of spherical equivalent correction in each group. CONCLUSIONS Dioptric adjustment of spherical equivalent correction according to cap thickness is essential to obtain similar refractive outcomes in myopic SMILE procedures. [J Refract Surg. 2019;35(3):153-160.].
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Eliasy A, Chen KJ, Vinciguerra R, Lopes BT, Abass A, Vinciguerra P, Ambrósio R, Roberts CJ, Elsheikh A. Determination of Corneal Biomechanical Behavior in-vivo for Healthy Eyes Using CorVis ST Tonometry: Stress-Strain Index. Front Bioeng Biotechnol 2019; 7:105. [PMID: 31157217 PMCID: PMC6532432 DOI: 10.3389/fbioe.2019.00105] [Citation(s) in RCA: 113] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 04/24/2019] [Indexed: 11/25/2022] Open
Abstract
Purpose: This study aims to introduce and clinically validate a new algorithm that can determine the biomechanical properties of the human cornea in vivo. Methods: A parametric study was conducted involving representative finite element models of human ocular globes with wide ranges of geometries and material biomechanical behavior. The models were subjected to different levels of intraocular pressure (IOP) and the action of external air puff produced by a non-contact tonometer. Predictions of dynamic corneal response under air pressure were analyzed to develop an algorithm that can predict the cornea's material behavior. The algorithm was assessed using clinical data obtained from 480 healthy participants where its predictions of material behavior were tested against variations in central corneal thickness (CCT), IOP and age, and compared against those obtained in earlier studies on ex-vivo human ocular tissue. Results: The algorithm produced a material stiffness parameter (Stress-Strain Index or SSI) that showed no significant correlation with both CCT (p > 0.05) and IOP (p > 0.05), but was significantly correlated with age (p < 0.01). The stiffness estimates and their variation with age were also significantly correlated (p < 0.01) with stiffness estimates obtained earlier in studies on ex-vivo human tissue. Conclusions: The study introduced and validated a new method for estimating the in vivo biomechanical behavior of healthy corneal tissue. The method can aid optimization of procedures that interfere mechanically with the cornea such as refractive surgeries and introduction of corneal implants.
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Affiliation(s)
- Ashkan Eliasy
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Kai-Jung Chen
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Riccardo Vinciguerra
- School of Engineering, University of Liverpool, Liverpool, United Kingdom.,St Paul's Eye Unit, Royal Liverpool and Broadgreen University Hospital, Liverpool, United Kingdom
| | - Bernardo T Lopes
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Ahmed Abass
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Paolo Vinciguerra
- Department of Biomedical Science, Humanitas University, Rozzano, Italy.,Eye Center, Humanitas Clinical and Research Center, Rozzano, Italy
| | - Renato Ambrósio
- Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, Brazil.,Department of Ophthalmology, Federal University of the State of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Science, Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, United Kingdom.,NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom.,School of Biological Science and Biomedical Engineering, Beihang University, Beijing, China
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Chen H, Liu G, Zhang S, Shen S, Luo Y, Li J, Roberts CJ, Sun M, Xu RX. Fundus-simulating phantom for calibration of retinal vessel oximetry devices. Appl Opt 2019; 58:3877-3885. [PMID: 31158206 DOI: 10.1364/ao.58.003877] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 04/10/2019] [Indexed: 06/09/2023]
Abstract
Retinal vessel oxygen supply is important for retinal tissue metabolism. Commonly used retinal vessel oximetry devices are based on dual-wavelength spectral measurement of oxyhemoglobin and deoxyhemoglobin. However, there is no traceable standard for reliable calibration of these devices. In this study, we developed a fundus-simulating phantom that closely mimicked the optical properties of human fundus tissues. Microchannels of precisely controlled topological structures were produced by soft lithography to simulate the retinal vasculature. Optical properties of the phantom were adjusted by adding scattering and absorption agents to simulate different concentrations of fundus pigments. The developed phantom was used to calibrate the linear correlation between oxygen saturation (SO2) level and optical density ratio in a dual-wavelength oximetry device. The obtained calibration factors were used to calculate the retinal vessel SO2 in both eyes of five volunteers aged between 24 and 27 years old. The test results showed that the mean arterial and venous SO2 levels after phantom calibration were coincident with those after empirical value calibration, indicating the potential clinical utility of the produced phantom as a calibration standard.
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Leão E, Ing Ren T, Lyra JM, Machado A, Koprowski R, Lopes B, Vinciguerra R, Vinciguerra P, Roberts CJ, Elsheikh A, Krysik K, Ambrósio R. Corneal deformation amplitude analysis for keratoconus detection through compensation for intraocular pressure and integration with horizontal thickness profile. Comput Biol Med 2019; 109:263-271. [PMID: 31096090 DOI: 10.1016/j.compbiomed.2019.04.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 01/25/2019] [Accepted: 04/20/2019] [Indexed: 01/03/2023]
Abstract
BACKGROUND The Corvis ST provides measurements of intraocular pressure (IOP) and a biomechanically-corrected IOP (bIOP). IOP influences corneal deflection amplitude (DA), which may affect the diagnosis of keratoconus. Compensating for IOP in DA values may improve the detection of keratoconus. METHODS 195 healthy eyes and 136 eyes with keratoconus were included for developing different approaches to distinguish normal and keratoconic corneas using attribute selection and discriminant function. The IOP compensation is proposed by dividing the DA by the IOP values. The first approaches include DA compensated for either IOP or bIOP and other parameters from the deformation corneal response (DCR). Another approach integrated the horizontal corneal thickness profile (HCTP). The best classifiers developed were applied in a validation database of 156 healthy eyes and 87 eyes with keratoconus. Results were compared with the current Corvis Biomechanical Index (CBI). RESULTS The best biomechanical approach used the DA values compensated by IOP (Approach 2) using a linear discriminant function and reached AUC 0.954, with a sensitivity of 88.2% and a specificity of 97.4%. When thickness horizontal profile data was integrated (Approach 4), the best function was the diagquadratic, resulting in an AUC of 0.960, with a sensitivity of 89.7% and a specificity of 96.4%. There was no significant difference in the results between approaches 2 and 4 with the CBI in the training and validation databases. CONCLUSIONS By compensating for the IOP, and with the horizontal thickness profile included or excluded, it was possible to generate a classifier based only on biomechanical information with a similar result to the CBI.
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Affiliation(s)
- Edileuza Leão
- Centro de Informática (CIn) - Universidade Federal de Pernambuco (UFPE) - v. Jornalista Aníbal Fernandes, Cidade Universitária, 50740-560, Recife, PE, Brazil; Universidade Estadual de Ciências da Saúde de Alagoas (UNCISAL), Brazil; Brazilian Study Group of Artificial Intelligence and Corneal Analysis (BrAIn), Brazil.
| | - Tsang Ing Ren
- Centro de Informática (CIn) - Universidade Federal de Pernambuco (UFPE) - v. Jornalista Aníbal Fernandes, Cidade Universitária, 50740-560, Recife, PE, Brazil; Brazilian Study Group of Artificial Intelligence and Corneal Analysis (BrAIn), Brazil
| | - João M Lyra
- Universidade Estadual de Ciências da Saúde de Alagoas (UNCISAL), Brazil; Brazilian Study Group of Artificial Intelligence and Corneal Analysis (BrAIn), Brazil
| | - Aydano Machado
- Instituto de Computação (IC) - Universidade Federal de Alagoas (UFAL), Brazil; Brazilian Study Group of Artificial Intelligence and Corneal Analysis (BrAIn), Brazil
| | - Robert Koprowski
- Department of Biomedical Computer Systems, University of Silesia, Faculty of Computer Science and Materials Science, Institute of Computer Science, Brazil
| | - Bernado Lopes
- Department of Ophthalmology of Federal University of São Paulo, São Paulo, Brazil; School of Engineering, University of Liverpool, Liverpool, UK
| | | | | | - Cynthia J Roberts
- Department of Ophthalmology Visual Science and Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, UK; National Institute for Health Research (NIHR) Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK; School of Biological Science and Biomedical Engineering, Beihang University, Beijing, China
| | - Katarzyna Krysik
- Department of Ophthalmology with Paediatric Unit, St. Barbara Hospital, Trauma Center, Sosnowiec, Poland
| | - Renato Ambrósio
- (d)Federal University of the State of Rio de Janeiro, Brazil; Department of Ophthalmology of Federal University of São Paulo, São Paulo, Brazil; Brazilian Study Group of Artificial Intelligence and Corneal Analysis (BrAIn), Brazil
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Lee H, Roberts CJ, Arba-Mosquera S, Kang DSY, Reinstein DZ, Kim TI. Relationship Between Decentration and Induced Corneal Higher-Order Aberrations Following Small-Incision Lenticule Extraction Procedure. Invest Ophthalmol Vis Sci 2019; 59:2316-2324. [PMID: 29847636 DOI: 10.1167/iovs.17-23451] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To investigate the amount of lenticule decentration following small-incision lenticule extraction (SMILE) by using the Keratron Scout tangential topography difference map, and the relationship between the magnitudes of total decentration and induced corneal higher-order aberrations (HOAs). Methods This retrospective observational case series study analyzed decentration values obtained from the Keratron Scout tangential topography difference map of 360 eyes (360 patients) that underwent SMILE. Root mean square total HOAs, third order coma aberration, fourth order spherical aberration, as well as individual coefficients for vertical and horizontal coma were measured preoperatively and 3-months postoperatively. Simple linear regression analysis and piecewise regression models were used to determine the relationship between the magnitudes of total decentration and induced corneal HOAs. Results The mean total decentration distance from the corneal vertex was 0.36 ± 0.22 mm (range, 0.02-1.27 mm). There were significant differences in total HOAs, coma, vertical and horizontal comas, and spherical aberration between preoperative and 3-month postoperative assessments. Significant relationships between the magnitudes of total decentration and induced corneal HOAs were noted. Subgroup analysis according to the degree of total decentration (group I, total decentered displacement ≤0.335 mm; and group II, total decentered displacement >0.335 mm) revealed that induced changes in total HOAs, coma, vertical coma, and spherical aberration were significantly larger in group II than in group I. Conclusions A minimal degree of decentration was closely related to a smaller induction of corneal HOAs. Efforts to optimize centration are critical for achieving better surgical outcomes in SMILE.
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Affiliation(s)
- Hun Lee
- Department of Ophthalmology, International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, South Korea.,The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea
| | - Cynthia J Roberts
- Department of Ophthalmology & Visual Science and Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio, United States
| | | | | | - Dan Z Reinstein
- London Vision Clinic, London, United Kingdom.,Department of Ophthalmology, Columbia University Medical Center, New York, New York, United States.,Centre Hospitalier National d'Ophtalmologie, Paris, France
| | - Tae-Im Kim
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea
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Sedaghat MR, Momeni-Moghaddam H, Ambrósio R, Roberts CJ, Yekta AA, Danesh Z, Reisdorf S, Khabazkhoob M, Heidari HR, Sadeghi J. Long-term Evaluation of Corneal Biomechanical Properties After Corneal Cross-linking for Keratoconus: A 4-Year Longitudinal Study. J Refract Surg 2019; 34:849-856. [PMID: 30540368 DOI: 10.3928/1081597x-20181012-02] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 10/10/2018] [Indexed: 11/20/2022]
Abstract
PURPOSE To compare the long-term changes in corneal biomechanics, topography, and tomography before and 4 years after corneal cross-linking (CXL) with the Dresden protocol and correlate these changes with visual acuity. METHODS In this longitudinal study, 18 eyes of 18 patients with progressive keratoconus who were treated with CXL were included. All patients received a standard ophthalmological examination and were examined by Placido disc-based topography, Scheimpflug tomography, and biomechanical assessments with the Corvis ST (OCULUS Optikgeräte GmbH, Wetzlar, Germany) and Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY) before and 4 years after CXL. The main outcome measures were dynamic corneal response (DCR) parameters obtained from the Corvis ST, corneal hysteresis (CH), corneal resistance factor (CRF), visual acuity, refraction, corneal curvature, and corneal thickness. RESULTS There were no significant differences in mean visual acuity, refraction, intraocular pressure, corneal topography, corneal astigmatism in both corneal surfaces, maximum keratometry, corneal thickness at apical and thinnest points, thickness profile indices, corneal volume, and specular microscopy before and 4 years after CXL (P > .05). Significant changes were observed in many DCR parameters, including radius at highest concavity and integrated inverse radius, both of which were consistent with stiffening. The CH and CRF values after CXL were not statistically significant. The new parameters using the Corvis ST include integrated inverse concave radius, which showed a significant decrease 1.07 ± 0.93 mm-1, consistent with stiffening. The corneal stiffness parameter at the first applanation, Ambrósio's Relational Thickness to the horizontal profile, deformation amplitude ratio, and Corvis Biomechanical Index as a combined biomechanical screening parameter did not show significant changes. CONCLUSIONS CXL is a minimally invasive treatment option to prevent keratoconus progression over 4 years. Pressure-derived biomechanical parameters obtained from the ORA did not show any change following CXL at 4 years of follow-up, whereas the Corvis ST DCR parameters detected changes in corneal biomechanical properties. [J Refract Surg. 2018;34(12):849-856.].
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Nguyen BA, Roberts CJ, Reilly MA. Biomechanical Impact of the Sclera on Corneal Deformation Response to an Air-Puff: A Finite-Element Study. Front Bioeng Biotechnol 2019; 6:210. [PMID: 30687701 PMCID: PMC6335394 DOI: 10.3389/fbioe.2018.00210] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 12/18/2018] [Indexed: 01/18/2023] Open
Abstract
Aim or Purpose: To describe the effect of varying scleral stiffness on the biomechanical deformation response of the cornea under air-puff loading via a finite-element (FE) model. Methods: A two-dimensional axisymmetric stationary FE model of the whole human eye was used to examine the effects varying scleral stiffness and intraocular pressure (IOP) on the maximum apical displacement of the cornea. The model was comprised of the cornea, sclera, vitreous, and surrounding air region. The velocity and pressure profiles of an air-puff from a dynamic Scheimpflug analyzer were replicated in the FE model, and the resultant profile was applied to deform the cornea in a multiphysics study (where the air-puff was first simulated before being applied to the corneal surface). IOP was simulated as a uniform pressure on the globe interior. The simulation results were compared to data from ex vivo scleral stiffening experiments with human donor globes. Results: The FE model predicted decreased maximum apical displacement with increased IOP and increased ratio of scleral-to-corneal Young's moduli. These predictions were in good agreement (within one standard deviation) with findings from ex vivo scleral stiffening experiments using human donor eyes. These findings demonstrate the importance of scleral material properties on the biomechanical deformation response of the cornea in air-puff induced deformation. Conclusion: The results of an air-puff induced deformation are often considered to be solely due to IOP and corneal properties. The current study showed that the stiffer the sclera, the greater will be the limitation on corneal deformation, separately from IOP. This may have important clinical implications to interpreting the response of the cornea under air-puff loading in pathologic conditions.
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Affiliation(s)
- B. Audrey Nguyen
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
| | - Cynthia J. Roberts
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
- Department of Ophthalmology & Visual Science, The Ohio State University, Columbus, OH, United States
| | - Matthew A. Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
- Department of Ophthalmology & Visual Science, The Ohio State University, Columbus, OH, United States
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Okon MD, Roberts CJ, Mahmoud AM, Springer AN, Small RH, McGregor JM, Katz SE. Characteristics of the cerebrospinal fluid pressure waveform and craniospinal compliance in idiopathic intracranial hypertension subjects. Fluids Barriers CNS 2018; 15:21. [PMID: 30064442 PMCID: PMC6069551 DOI: 10.1186/s12987-018-0106-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 07/14/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Idiopathic intracranial hypertension (IIH) is a condition of abnormally high intracranial pressure with an unknown etiology. The objective of this study is to characterize craniospinal compliance and measure the cerebrospinal fluid (CSF) pressure waveform as CSF is passively drained during a diagnostic and therapeutic lumbar puncture (LP) in IIH. METHODS Eighteen subjects who met the Modified Dandy Criteria, including papilledema and visual field loss, received an ultrasound guided LP where CSF pressure (CSFP) was recorded at each increment of CSF removal. Joinpoint regression models were used to calculate compliance from CSF pressure and the corresponding volume removed at each increment for each subject. Twelve subjects had their CSFP waveform recorded with an electronic transducer. Body mass index, mean CSFP, and cerebral perfusion pressure (CPP) were also calculated. T-tests were used to compare measurements, and correlations were performed between parameters. RESULTS Cerebrospinal fluid pressure, CSFP pulse amplitude (CPA), and CPP were found to be significantly different (p < 0.05) before and after the LP. CSFP and CPA decreased after the LP, while CPP increased. The craniospinal compliance significantly increased (p < 0.05) post-LP. CPA and CSFP were significantly positively correlated. CONCLUSIONS Both low craniospinal compliance (at high CSFP) and high craniospinal compliance (at low CSFP) regions were determined. The CSFP waveform morphology in IIH was characterized and CPA was found to be positively correlated to the magnitude of CSFP. Future studies will investigate how craniospinal compliance may correlate to symptoms and/or response to therapy in IIH subjects.
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Affiliation(s)
- Monica D Okon
- Department of Biomedical Engineering, The Ohio State University, 1080 Carmack Rd, Columbus, OH, 43210, USA
| | - Cynthia J Roberts
- Department of Biomedical Engineering, The Ohio State University, 1080 Carmack Rd, Columbus, OH, 43210, USA. .,Department of Ophthalmology & Visual Science, The Ohio State University, 915 Olentangy River Rd, Columbus, OH, 43212, USA.
| | - Ashraf M Mahmoud
- Department of Biomedical Engineering, The Ohio State University, 1080 Carmack Rd, Columbus, OH, 43210, USA.,Department of Ophthalmology & Visual Science, The Ohio State University, 915 Olentangy River Rd, Columbus, OH, 43212, USA
| | - Andrew N Springer
- Department of Anesthesiology, The Ohio State University, 410W. 10th Avenue, Columbus, OH, 43210, USA
| | - Robert H Small
- Department of Biomedical Engineering, The Ohio State University, 1080 Carmack Rd, Columbus, OH, 43210, USA.,Department of Anesthesiology, The Ohio State University, 410W. 10th Avenue, Columbus, OH, 43210, USA
| | - John M McGregor
- Department of Neurosurgery, The Ohio State University, 1581 Dodd Drive, Columbus, OH, 43210, USA
| | - Steven E Katz
- Ohio Neuro-Ophthalmology, Orbital Disease & Oculoplastics, 3545 Olentangy River Rd, Suite 200, Columbus, OH, 43214, USA
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Kang DSY, Lee H, Reinstein DZ, Roberts CJ, Arba-Mosquera S, Archer TJ, Kim EK, Seo KY, Kim TI. Comparison of the Distribution of Lenticule Decentration Following SMILE by Subjective Patient Fixation or Triple Marking Centration. J Refract Surg 2018; 34:446-452. [DOI: 10.3928/1081597x-20180517-02] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 05/07/2018] [Indexed: 11/20/2022]
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Kupeli N, Schmidt UH, Campbell IC, Chilcot J, Roberts CJ, Troop NA. The impact of an emotionally expressive writing intervention on eating pathology in female students. Health Psychol Behav Med 2018; 6:162-179. [PMID: 30009092 PMCID: PMC6030678 DOI: 10.1080/21642850.2018.1491797] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 05/23/2018] [Indexed: 11/21/2022] Open
Abstract
Introduction: Previous research demonstrating emotional influences on eating and weight suggest that emotionally expressive writing may have a significant impact on reducing risk of eating pathology. This study examined the effects of writing about Intensely Positive Experiences on weight and disordered eating during a naturalistic stressor. Method: Seventy-one female students completed an expressive or a control writing task before a period of exams. Both groups were compared on BMI (kg/m2) and the Eating Disorder Examination – Questionnaire (EDE-Q) before the writing task and at 8-week follow-up. A number of secondary analyses were also examined (to identify potential mediators) including measures of attachment, social rank, self-criticism and self-reassurance, stress and mood. Results: There was a significant effect of intervention on changes in the subscales of the EDE-Q (p = .03). Specifically, expressive writers significantly reduced their dietary restraint while those in the control group did not. There was no significant effect of the intervention on changes in BMI or the other subscales of the EDE-Q (Eating, Weight and Shape Concern). There was also no effect of writing on any of the potential mediators in the secondary analyses. Discussion: Emotionally expressive writing may reduce the risk of dietary restraint in women but these findings should be accepted with caution. It is a simple and light touch intervention that has the potential to be widely applied. However, it remains for future research to replicate these results and to identify the mechanisms of action.
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Affiliation(s)
- N Kupeli
- Marie Curie Palliative Care Research Department, Division of Psychiatry, University College London, London, UK
| | - U H Schmidt
- Section of Eating Disorders, Institute of Psychiatry, Psychology & Neuroscience (IoPPN), King's College London, London, UK
| | - I C Campbell
- Section of Eating Disorders, Institute of Psychiatry, Psychology & Neuroscience (IoPPN), King's College London, London, UK
| | - J Chilcot
- Health Psychology Section, Institute of Psychiatry, Psychology & Neuroscience (IoPPN), King's College London, London, UK
| | - C J Roberts
- School of Health and Social Science, London South Bank University, London, UK
| | - N A Troop
- Department of Psychology and Sport Sciences, University of Hertfordshire, UK
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Eliasy A, Chen KJ, Vinciguerra R, Maklad O, Vinciguerra P, Ambrósio R, Roberts CJ, Elsheikh A. Ex-vivo experimental validation of biomechanically-corrected intraocular pressure measurements on human eyes using the CorVis ST. Exp Eye Res 2018; 175:98-102. [PMID: 29908883 DOI: 10.1016/j.exer.2018.06.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 05/30/2018] [Accepted: 06/14/2018] [Indexed: 11/17/2022]
Abstract
The purpose of this study was to assess the validity of the Corvis ST (Oculus; Wetzlar, Germany) biomechanical correction algorithm (bIOP) in determining intraocular pressure (IOP) using experiments on ex-vivo human eyes. Five ex-vivo human ocular globes (age 69 ± 3 years) were obtained and tested within 3-5 days post mortem. Using a custom-built inflation rig, the internal pressure of the eyes was controlled mechanically and measured using the CorVis ST (CVS-IOP). The CVS-IOP measurements were then corrected to produce bIOP, which was developed for being less affected by variations in corneal biomechanical parameters, including tissue thickness and material properties. True IOP (IOPt) was defined as the pressure inside of the globe as monitored using a fixed pressure transducer. Statistical analyses were performed to assess the accuracy of both CVS-IOP and bIOP, and their correlation with corneal thickness. While no significant differences were found between bIOP and IOPt (0.3 ± 1.6 mmHg, P = 0.989) using ANOVA and Bonferroni Post-Hoc test, the differences between CVS-IOP and IOPt were significant (7.5 ± 3.2 mmHg, P < 0.001). Similarly, bIOP exhibited no significant correlation with central corneal thickness (p = 0.756), whereas CVS-IOP was significantly correlated with the thickness (p < 0.001). The bIOP correction has been successful in providing close estimates of true IOP in ex-vivo tests conducted on human donor eye globes, and in reducing association with the cornea's thickness.
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Affiliation(s)
- Ashkan Eliasy
- School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK.
| | - Kai-Jung Chen
- School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK
| | - Riccardo Vinciguerra
- School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK; St Paul's Eye Unit, Royal Liverpool and Broadgreen University Hospital, Liverpool, UK
| | - Osama Maklad
- School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK
| | - Paolo Vinciguerra
- Department of Biomedical Science-Humanitas University, Via Manzoni 56, Rozzano, MI, Italy; Eye Center, Humanitas Clinical and Research Center, Via Manzoni 56, Rozzano, MI, Italy
| | - Renato Ambrósio
- Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, Brazil; Department of Ophthalmology, Federal University of São Paulo (UNIFESP), São Paulo, Brazil; Department of Ophthalmology, Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, Brazil
| | - Cynthia J Roberts
- Department of Ophthalmology & Visual Science, Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK; NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, UK
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Seven I, Vahdati A, Pedersen IB, Vestergaard A, Hjortdal J, Roberts CJ, Dupps WJ. Contralateral Eye Comparison of SMILE and Flap-Based Corneal Refractive Surgery: Computational Analysis of Biomechanical Impact. J Refract Surg 2018; 33:444-453. [PMID: 28681903 DOI: 10.3928/1081597x-20170504-01] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 03/23/2017] [Indexed: 11/20/2022]
Abstract
PURPOSE Computational analyses were performed to quantify and directly compare the biomechanical impact of flapless and flap-based procedures in a series of patients undergoing small incision lenticule extraction (SMILE) in one eye and flap-based femtosecond lenticule extraction in the other. METHODS Tomographic data from 10 eyes of 5 patients undergoing femtosecond laser refractive lenticule extraction for myopic astigmatism with or without a stromal flap (femtosecond lenticule extraction in one eye, SMILE in the contralateral eye) were used to generate computational models. Inverse finite element analyses were performed at physiologic intraocular pressure followed by forward analyses at elevated intraocular pressure to assess corneal displacement and stress under differential loading. Case-specific treatment settings were incorporated. Preoperative material constants were obtained through inverse finite element analyses, and the surgically induced change in fiber stiffness within each flap was determined by minimization of the error between the simulated and actual 6-month topographic outcomes. RESULTS Flap-based procedures produced a 49% (range: 2% to 87%) greater mean reduction in effective stromal collagen fiber stiffness within the flap region than contralateral SMILE cases. Lower stresses and deformations were observed within the residual stromal bed in SMILE cases than in flap-based cases. Stromal bed displacements and stresses were more affected by a loading increase in flap-based eyes than flapless eyes. CONCLUSIONS Intrastromal flapless procedures had less impact on anterior stromal collagen mechanics and resulted in lower stromal bed displacements and stresses than flap-based procedures in contralateral eyes. However, biomechanical impact varied widely between individuals and this reinforces the need for individualized assessment of ectasia risk. [J Refract Surg. 2017;33(7):444-453].
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Chen KJ, Joda A, Vinciguerra R, Eliasy A, Sefat SMM, Kook D, Geraghty B, Roberts CJ, Elsheikh A. Clinical evaluation of a new correction algorithm for dynamic Scheimpflug analyzer tonometry before and after laser in situ keratomileusis and small-incision lenticule extraction. J Cataract Refract Surg 2018; 44:581-588. [PMID: 29685776 DOI: 10.1016/j.jcrs.2018.01.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 01/04/2018] [Accepted: 01/05/2018] [Indexed: 10/17/2022]
Abstract
PURPOSE To compare a biomechanically corrected intraocular pressure (bIOP) algorithm provided by the dynamic Scheimpflug analyzer (Corvis ST) with Goldmann applanation tonometry IOP (Goldmann IOP) and standard dynamic Scheimpflug analyzer IOP measurements before and after laser in situ keratomileusis (LASIK) and refractive lenticule extraction small-incision lenticule extraction (SMILE) surgeries. SETTING Smile Eye Clinic, Munich, Germany, and University of Liverpool, Liverpool, United Kingdom. DESIGN Retrospective case series. METHODS Patients scheduled for LASIK and patients scheduled for small-incision lenticule extraction for myopia or myopic astigmatism were included. The preoperative and postoperative evaluations included Goldmann, Scheimpflug tomography, and dynamic Scheimpflug analyzer IOP measurements. RESULTS The study comprised 14 patients in the LASIK group and 22 patients in the small-incision lenticule extraction group. Preoperative Goldmann IOP and Scheimpflug analyzer IOP values showed significant positive correlation with central corneal thickness (CCT) (P = .05 for LASIK; P = .003 for small-incision lenticule extraction). No significant correlation was found between bIOP and CCT (P > .05). After both surgeries, there were significant decreases in Goldmann IOP (-3.2 mm Hg ± 3.4 [SD] and -3.2 ± 2.1 mm Hg, respectively; both P < .001) and Scheimpflug analyzer IOP (-3.7 ± 2.1 mm Hg and -3.3 ± 2.0 mm Hg, respectively, both P < .001) compared with preoperative readings, whereas bIOP did not differ significantly (0.1 ± 2.1 mm Hg and 0.8 ± 1.8 mm Hg, respectively; P = .80 and P = .273, respectively). CONCLUSIONS The bIOP readings before and after LASIK and small-incision lenticule extraction were neither significantly different nor correlated with CCT. In contrast, both Goldmann IOP and Scheimpflug analyzer IOP had significant reductions postoperatively and showed significant correlation with CCT preoperatively.
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Affiliation(s)
- Kai-Jung Chen
- From the School of Engineering (Chen, Joda, Eliasy, Geraghty, Elsheikh), University of Liverpool and the St. Paul's Eye Unit (Vinciguerra), Royal Liverpool and Broadgreen University Hospital, Liverpool, and the NIHR Biomedical Research Centre for Ophthalmology (Elsheikh), Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom; the College of Engineering (Joda), King Faisal University, Al-Ahsa, Kingdom of Saudi Arabia; Smile Eye Clinic (Sefat, Kook) and the Department of Ophthalmology (Kook), Ludwig-Maximilians-University, Munich, Germany; the Department of Ophthalmology & Visual Science (Roberts), Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA
| | - Akram Joda
- From the School of Engineering (Chen, Joda, Eliasy, Geraghty, Elsheikh), University of Liverpool and the St. Paul's Eye Unit (Vinciguerra), Royal Liverpool and Broadgreen University Hospital, Liverpool, and the NIHR Biomedical Research Centre for Ophthalmology (Elsheikh), Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom; the College of Engineering (Joda), King Faisal University, Al-Ahsa, Kingdom of Saudi Arabia; Smile Eye Clinic (Sefat, Kook) and the Department of Ophthalmology (Kook), Ludwig-Maximilians-University, Munich, Germany; the Department of Ophthalmology & Visual Science (Roberts), Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA
| | - Riccardo Vinciguerra
- From the School of Engineering (Chen, Joda, Eliasy, Geraghty, Elsheikh), University of Liverpool and the St. Paul's Eye Unit (Vinciguerra), Royal Liverpool and Broadgreen University Hospital, Liverpool, and the NIHR Biomedical Research Centre for Ophthalmology (Elsheikh), Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom; the College of Engineering (Joda), King Faisal University, Al-Ahsa, Kingdom of Saudi Arabia; Smile Eye Clinic (Sefat, Kook) and the Department of Ophthalmology (Kook), Ludwig-Maximilians-University, Munich, Germany; the Department of Ophthalmology & Visual Science (Roberts), Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA
| | - Ashkan Eliasy
- From the School of Engineering (Chen, Joda, Eliasy, Geraghty, Elsheikh), University of Liverpool and the St. Paul's Eye Unit (Vinciguerra), Royal Liverpool and Broadgreen University Hospital, Liverpool, and the NIHR Biomedical Research Centre for Ophthalmology (Elsheikh), Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom; the College of Engineering (Joda), King Faisal University, Al-Ahsa, Kingdom of Saudi Arabia; Smile Eye Clinic (Sefat, Kook) and the Department of Ophthalmology (Kook), Ludwig-Maximilians-University, Munich, Germany; the Department of Ophthalmology & Visual Science (Roberts), Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA.
| | - Shervin Mir Mohi Sefat
- From the School of Engineering (Chen, Joda, Eliasy, Geraghty, Elsheikh), University of Liverpool and the St. Paul's Eye Unit (Vinciguerra), Royal Liverpool and Broadgreen University Hospital, Liverpool, and the NIHR Biomedical Research Centre for Ophthalmology (Elsheikh), Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom; the College of Engineering (Joda), King Faisal University, Al-Ahsa, Kingdom of Saudi Arabia; Smile Eye Clinic (Sefat, Kook) and the Department of Ophthalmology (Kook), Ludwig-Maximilians-University, Munich, Germany; the Department of Ophthalmology & Visual Science (Roberts), Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA
| | - Daniel Kook
- From the School of Engineering (Chen, Joda, Eliasy, Geraghty, Elsheikh), University of Liverpool and the St. Paul's Eye Unit (Vinciguerra), Royal Liverpool and Broadgreen University Hospital, Liverpool, and the NIHR Biomedical Research Centre for Ophthalmology (Elsheikh), Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom; the College of Engineering (Joda), King Faisal University, Al-Ahsa, Kingdom of Saudi Arabia; Smile Eye Clinic (Sefat, Kook) and the Department of Ophthalmology (Kook), Ludwig-Maximilians-University, Munich, Germany; the Department of Ophthalmology & Visual Science (Roberts), Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA
| | - Brendan Geraghty
- From the School of Engineering (Chen, Joda, Eliasy, Geraghty, Elsheikh), University of Liverpool and the St. Paul's Eye Unit (Vinciguerra), Royal Liverpool and Broadgreen University Hospital, Liverpool, and the NIHR Biomedical Research Centre for Ophthalmology (Elsheikh), Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom; the College of Engineering (Joda), King Faisal University, Al-Ahsa, Kingdom of Saudi Arabia; Smile Eye Clinic (Sefat, Kook) and the Department of Ophthalmology (Kook), Ludwig-Maximilians-University, Munich, Germany; the Department of Ophthalmology & Visual Science (Roberts), Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA
| | - Cynthia J Roberts
- From the School of Engineering (Chen, Joda, Eliasy, Geraghty, Elsheikh), University of Liverpool and the St. Paul's Eye Unit (Vinciguerra), Royal Liverpool and Broadgreen University Hospital, Liverpool, and the NIHR Biomedical Research Centre for Ophthalmology (Elsheikh), Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom; the College of Engineering (Joda), King Faisal University, Al-Ahsa, Kingdom of Saudi Arabia; Smile Eye Clinic (Sefat, Kook) and the Department of Ophthalmology (Kook), Ludwig-Maximilians-University, Munich, Germany; the Department of Ophthalmology & Visual Science (Roberts), Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA
| | - Ahmed Elsheikh
- From the School of Engineering (Chen, Joda, Eliasy, Geraghty, Elsheikh), University of Liverpool and the St. Paul's Eye Unit (Vinciguerra), Royal Liverpool and Broadgreen University Hospital, Liverpool, and the NIHR Biomedical Research Centre for Ophthalmology (Elsheikh), Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom; the College of Engineering (Joda), King Faisal University, Al-Ahsa, Kingdom of Saudi Arabia; Smile Eye Clinic (Sefat, Kook) and the Department of Ophthalmology (Kook), Ludwig-Maximilians-University, Munich, Germany; the Department of Ophthalmology & Visual Science (Roberts), Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA
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