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Wang C, Shen M, Song Y, Chang L, Yang Y, Li Y, Liu T, Wang Y. Biaxial hyperelastic and anisotropic behaviors of the corneal anterior central stroma along the preferential fibril orientations. Part I: Measurement and calibration of personalized stress-strain curves. Exp Eye Res 2023; 236:109677. [PMID: 37827443 DOI: 10.1016/j.exer.2023.109677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 09/09/2023] [Accepted: 10/09/2023] [Indexed: 10/14/2023]
Abstract
Lacking specimens is the biggest limitation of studying the mechanical behaviors of human corneal. Extracting stress-strain curves is the crucial step in investigating hyperelastic and anisotropic properties of human cornea. 15 human corneal specimens extracted from the small incision lenticule extraction (SMILE) surgery were applied in this study. To accurately measure the personalized true stress-strain curve using corneal lenticules, the digital image correlation (DIC) method and finite element method were used to calibrate the stress and the strain of the biaxial extension test. The hyperelastic load-displacement curves obtained from the biaxial extension test were performed in preferential fibril orientations, which are arranged along the nasal-temporal (NT) and the superior-inferior (SI) directions within the anterior central stroma. The displacement and strain fields were accurately calibrated and calculated using the digital image correlation (DIC) method. A conversion equation was given to convert the effective engineering strain to the true strain. The stress field distribution, which was simulated using the finite element method, was verified. Based on this, the effective nominal stress with personalized characteristics was calibrated. The personalized stress-strain curves containing individual characteristic, like diopter and anterior surface curvature, was accurately measured in this study. These results provide an experimental method using biaxial tensile test with corneal lenticules. It is the foundation for investigating the hyperelasticity and anisotropy of the central anterior stroma of human cornea.
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Affiliation(s)
- Congzheng Wang
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300350, China
| | - Min Shen
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300350, China.
| | - Yi Song
- Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Nankai University, Tianjin, 300020, China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, 300070, China
| | - Le Chang
- Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Nankai University, Tianjin, 300020, China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, 300070, China
| | - Yaqing Yang
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300350, China
| | - Yikuan Li
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300350, China
| | - Taiwei Liu
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin, 300350, China; Department of Engineering Mechanics, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, 800 Dong Chuan Road, Shanghai, 200240, China
| | - Yan Wang
- Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Nankai University, Tianjin, 300020, China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, 300070, China
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Yang F, Dong Y, Bai C, Alzogool M, Wang Y. Bibliometric and visualized analysis of myopic corneal refractive surgery research: from 1979 to 2022. Front Med (Lausanne) 2023; 10:1141438. [PMID: 37575980 PMCID: PMC10416457 DOI: 10.3389/fmed.2023.1141438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 07/14/2023] [Indexed: 08/15/2023] Open
Abstract
Background Myopic corneal refractive surgery is one of the most prevalent ophthalmic procedures for correcting ametropia. This study aimed to perform a bibliometric analysis of research in the field of corneal refractive surgery over the past 40 years in order to describe the current international status and to identify most influential factors, while highlighting research hotspots. Methods A bibliometric analysis based on the Web of Science Core Collection (WoSCC) was used to analyze the publication trends in research related to myopic corneal refractive surgery. VOSviewer v.1.6.10 was used to construct the knowledge map in order to visualize the publications, distribution of countries, international collaborations, author productivity, source journals, cited references, keywords, and research hotspots in this field. Results A total of 4,680 publications on myopic corneal refractive surgery published between 1979 and 2022 were retrieved. The United States has published the most papers, with Emory University contributing to the most citations. The Journal of Cataract and Refractive Surgery published the greatest number of articles, and the top 10 cited references mainly focused on outcomes and wound healing in refractive surgery. Previous research emphasized "radial keratotomy (RK)" and excimer laser-associated operation methods. The keywords containing femtosecond (FS) laser associated with "small incision lenticule extraction (SMILE)" and its "safety" had higher burst strength, indicating a shift of operation methods and coinciding with the global trends in refractive surgery. The document citation network was clustered into five groups: (1) outcomes of refractive surgery: (2) preoperative examinations for refractive surgery were as follows: (3) complications of myopic corneal refractive surgery; (4) corneal wound healing and cytobiology research related to photorefractive laser keratotomy; and (5) biomechanics of myopic corneal refractive surgery. Conclusion The bibliometric analysis in this study may provide scholars with valuable to information and help them better understand the global trends in myopic corneal refractive surgery research frontiers. Two stages of rapid development occurred around 1991 and 2013, shortly after the innovation of PRK and SMILE surgical techniques. The most cited articles mainly focused on corneal wound healing, clinical outcomes, ocular aberration, corneal ectasia, and corneal topography, representing the safety of the new techniques.
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Affiliation(s)
- Fang Yang
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
- Department of Ophthalmology, Renmin Hospital, Hubei University of Medicine, Shiyan, China
| | - Yi Dong
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
- Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Tianjin, China
| | - Chen Bai
- Department of General Surgery, Taihe Hospital, Hubei University of Medicine, Shiyan, China
| | - Mohammad Alzogool
- Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Tianjin, China
- School of Medicine, Nankai University, Tianjin, China
| | - Yan Wang
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
- Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Tianjin, China
- Nankai Eye Institute, Nankai University, Tianjin, China
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Li F, Wang K, Liu Z. In Vivo Biomechanical Measurements of the Cornea. BIOENGINEERING (BASEL, SWITZERLAND) 2023; 10:bioengineering10010120. [PMID: 36671692 PMCID: PMC9854753 DOI: 10.3390/bioengineering10010120] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/03/2022] [Revised: 01/11/2023] [Accepted: 01/13/2023] [Indexed: 01/18/2023]
Abstract
In early corneal examinations, the relationships between the morphological and biomechanical features of the cornea were unclear. Although consistent links have been demonstrated between the two in certain cases, these are not valid in many diseased states. An accurate assessment of the corneal biomechanical properties is essential for understanding the condition of the cornea. Studies on corneal biomechanics in vivo suggest that clinical problems such as refractive surgery and ectatic corneal disease are closely related to changes in biomechanical parameters. Current techniques are available to assess the mechanical characteristics of the cornea in vivo. Accordingly, various attempts have been expended to obtain the relevant mechanical parameters from different perspectives, using the air-puff method, ultrasound, optical techniques, and finite element analyses. However, a measurement technique that can comprehensively reflect the full mechanical characteristics of the cornea (gold standard) has not yet been developed. We review herein the in vivo measurement techniques used to assess corneal biomechanics, and discuss their advantages and limitations to provide a comprehensive introduction to the current state of technical development to support more accurate clinical decisions.
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Affiliation(s)
- Fanshu Li
- Beijing Key Laboratory of Restoration of Damaged Ocular Nerve, Health Science Center, Peking University, Beijing 100191, China
| | - Kehao Wang
- Beijing Advanced Innovation Center for Biomedical Engineering, School of Engineering Medicine, Beihang University, Beijing 100191, China
| | - Ziyuan Liu
- Beijing Key Laboratory of Restoration of Damaged Ocular Nerve, Health Science Center, Peking University, Beijing 100191, China
- Correspondence:
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Choe GS, Kim KY. Comparison of Anterior Segment Measurements between Scheimpflug-Placido Camera and New Swept-source Optical Coherence Tomography. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2022. [DOI: 10.3341/jkos.2022.63.1.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Purpose: We compared anterior segment measurements obtained using a Scheimpflug-Placido topographer (SIRIUS®, Costruzione Strumenti Oftalmici, Florence, Italy) and a new anterior module for a swept-source optical coherence tomography system (ANTERION®, Heidelberg Engineering Inc., Heidelberg, Germany).Methods: Anterior segment measurements were evaluated in 74 eyes of 101 patients with the two devices. Central corneal thickness (CCT), anterior chamber depth (ACD), corneal refractive power (K), J0 (Jackson cross-cylinder with axes at 180° and 90°), J45 vector (Jackson cross-cylinder with axes at 45° and 135°), and white-to-white corneal diameter (WTW) measurements obtained using the SIRIUS® system and the new anterior segment module of ANTERION® were compared.Results: The mean CCTs measured by SIRIUS® and ANTERION® were 558.69 ± 44.65 and 540.26 ± 36.57 μm, respectively. The difference was statistically significant (p < 0.005), and there were high correlations between the two methods (r = 0.915, p < 0.001). The mean ACD measurements were 3.34 ± 0.53 and 3.34 ± 0.51 mm (p = 0.856), respectively, for SIRIUS® and ANTERION®. The measurements were strongly correlated (r = 0.966, p < 0.001). The measurements of WTW, total mean K, and J0 obtained with the two systems differed significantly (p < 0.005, p = 0.017, and p < 0.005, respectively), with high correlations between the two systems (r = 0.875, r = 0.967, and r = 0.933, respectively; all p < 0.001).Conclusions: There were significant differences in measurements of K, CCT, WTW, and J0 between the two devices. Agreement analysis suggests that SIRIUS® and ANTERION® should not be used interchangeably.
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Lin CP, Tung HF, Chen HL, Liu YL. Corneal ectasia after an incomplete flap creation in an abandoned laser-assisted in situ keratomileusis. Taiwan J Ophthalmol 2022; 13:97-100. [DOI: 10.4103/2211-5056.364565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 09/07/2022] [Indexed: 12/24/2022] Open
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Moshirfar M, Tukan AN, Bundogji N, Liu HY, McCabe SE, Ronquillo YC, Hoopes PC. Ectasia After Corneal Refractive Surgery: A Systematic Review. Ophthalmol Ther 2021; 10:753-776. [PMID: 34417707 PMCID: PMC8589911 DOI: 10.1007/s40123-021-00383-w] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 08/02/2021] [Indexed: 01/03/2023] Open
Abstract
INTRODUCTION The incidence of ectasia following refractive surgery is unclear. This review sought to determine the worldwide rates of ectasia after photorefractive keratectomy (PRK), laser-assisted in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE) based on reports in the literature. METHODS A systematic review was conducted according to modified Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Publications were identified by a search of eight electronic databases for relevant terms between 1984 and 2021. Patient characteristics and preoperative values including manifest refractive spherical refractive equivalent (MRSE), central corneal thickness (CCT), anterior keratometry, postoperative residual stromal bed (RSB), and percent tissue altered (PTA) were summarized. In addition, annual rates of each refractive surgery were determined, and incidence of post-refractive ectasia for each type was calculated using the number of ectatic eyes identified in the literature. RESULTS In total, 57 eyes (70 eyes including those with preoperative risk factors for ectasia) were identified to have post-PRK ectasia, while 1453 eyes (1681 eyes including risk factors) had post-LASIK ectasia, and 11 eyes (19 eyes including risk factors) had post-SMILE ectasia. Cases of refractive surgery performed annually were estimated as 283,920 for PRK, 1,608,880 for LASIK, and 96,750 for SMILE. Reported post-refractive ectasia in eyes without preoperative identifiable risk factors occurred with the following incidences: 20 per 100,000 eyes in PRK, 90 per 100,000 eyes in LASIK, and 11 per 100,000 eyes in SMILE. The rate of ectasia in LASIK was found to be 4.5 times higher than that of PRK. CONCLUSION Post-refractive ectasia occurs at lower rates in eyes undergoing PRK than LASIK. Although SMILE appears to have the lowest rate of ectasia, the number of cases already reported since its recent approval suggests that post-SMILE ectasia may become a concern. Considering that keratoconus is a spectrum of disease, pre-existing keratoconus may play a larger role in postoperative ectasia than previously accounted for in the literature.
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Affiliation(s)
- Majid Moshirfar
- Hoopes Vision Research Center, Hoopes Vision, 11820 S. State Street Suite #200, Draper, UT, 84020, USA.
- John A. Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT, USA.
- Utah Lions Eye Bank, Murray, UT, USA.
| | - Alyson N Tukan
- University of Arizona College of Medicine-Phoenix, Phoenix, AZ, USA
| | - Nour Bundogji
- University of Arizona College of Medicine-Phoenix, Phoenix, AZ, USA
| | - Harry Y Liu
- McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Shannon E McCabe
- Hoopes Vision Research Center, Hoopes Vision, 11820 S. State Street Suite #200, Draper, UT, 84020, USA
- Mission Hills Eye Center, Pleasant Hill, CA, USA
| | - Yasmyne C Ronquillo
- Hoopes Vision Research Center, Hoopes Vision, 11820 S. State Street Suite #200, Draper, UT, 84020, USA
| | - Phillip C Hoopes
- Hoopes Vision Research Center, Hoopes Vision, 11820 S. State Street Suite #200, Draper, UT, 84020, USA
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Woo SE, Lee SH. A Comparison of Central Corneal Thickness Measurements and Measurement Repeatability Using Three Imaging Modalities. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2021. [DOI: 10.3341/jkos.2021.62.2.184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Mohamadpour M, Khorrami-Nejad M, Kiarudi MY, Khosravi K. Evaluating the Ectasia Risk Score System in Cancelled Laser In Situ Keratomileusis Candidates. J Ophthalmic Vis Res 2020; 15:481-485. [PMID: 33133438 PMCID: PMC7591850 DOI: 10.18502/jovr.v15i4.7788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 07/27/2020] [Indexed: 11/29/2022] Open
Abstract
Purpose To evaluate the ectasia risk score system in cancelled laser in situ keratomileusis (LASIK) candidates at an academic hospital. Methods LASIK candidates who had been cancelled by a surgeon considering the patient age, preoperative central corneal thickness, residual stromal bed thickness, or preoperative manifest refraction spherical equivalent were retrospectively reviewed, and their Randleman ectasia risk score system score was calculated. Results The mean ectasia score of 194 eyes (97 patients) was 4.5 ± 2.67; 40 (20.6%), 46 (23.7%), and 108 (55.7%) eyes were classified as low-, moderate-, and high-risk eyes, respectively. The topography was abnormal in 69% of the patients. The mean manifest refraction spherical equivalent, central corneal thickness, and estimated residual stromal bed thickness were 4 (+0.50 to –15.50) diopters, 520 (439 to 608) µm, and 312.38 (61.5 to 424.12) µm, respectively. The main cause of cancellation in low- and moderate-risk patients (86 eyes) was the presence of unstable refractive error in the past year. Conclusion Although promising, some other criteria, such as stable refraction, should be added to this scoring system to achieve greater practicality since a main cause of cancelling LASIK candidates in this study was the presence of unstable refraction.
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Affiliation(s)
- Mehrdad Mohamadpour
- Translational Ophthalmology Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Masoud Khorrami-Nejad
- Translational Ophthalmology Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran.,School of Rehabilitation, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad Yaser Kiarudi
- Translational Ophthalmology Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Keivan Khosravi
- Translational Ophthalmology Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran
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Jin Z, Chen S, Dai Y, Bao C, Ye S, Zhou Y, Wang Y, Huang S, Wang Y, Shen M, Zhu D, Lu F. In vivo noninvasive measurement of spatially resolved corneal elasticity in human eyes using Lamb wave optical coherence elastography. JOURNAL OF BIOPHOTONICS 2020; 13:e202000104. [PMID: 32368840 DOI: 10.1002/jbio.202000104] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 04/24/2020] [Accepted: 04/29/2020] [Indexed: 05/23/2023]
Abstract
Current elastography techniques are limited in application to accurately assess spatially resolved corneal elasticity in vivo for human eyes. The air-puff optical coherence elastography (OCE) with an eye motion artifacts correction algorithm is developed to distinguish the in vivo cornea vibration from the eye motion and visualize the Lamb wave propagation clearly in healthy subjects. Based on the Lamb wave model, the phase velocity dispersion curve in the high-frequency is calculated to obtain spatially resolved corneal elasticity accurately with high repeatability. It is found that the corneal elasticity has regional variations and is correlated with intraocular pressure, which suggests that the method has the potential to provide noninvasive measurement of spatially resolved corneal elasticity in clinical practice.
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Affiliation(s)
- Zi Jin
- School of Ophthalmology and Optometry, Wenzhou Medical University, Zhejiang, China
| | - Sisi Chen
- School of Ophthalmology and Optometry, Wenzhou Medical University, Zhejiang, China
| | - Yingying Dai
- School of Ophthalmology and Optometry, Wenzhou Medical University, Zhejiang, China
| | - Chenhong Bao
- School of Ophthalmology and Optometry, Wenzhou Medical University, Zhejiang, China
| | - Shuling Ye
- School of Ophthalmology and Optometry, Wenzhou Medical University, Zhejiang, China
| | - Yuheng Zhou
- School of Ophthalmology and Optometry, Wenzhou Medical University, Zhejiang, China
| | - Yiyi Wang
- School of Ophthalmology and Optometry, Wenzhou Medical University, Zhejiang, China
| | - Shenghai Huang
- School of Ophthalmology and Optometry, Wenzhou Medical University, Zhejiang, China
| | - Yuanyuan Wang
- School of Ophthalmology and Optometry, Wenzhou Medical University, Zhejiang, China
| | - Meixiao Shen
- School of Ophthalmology and Optometry, Wenzhou Medical University, Zhejiang, China
| | - Dexi Zhu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Zhejiang, China
| | - Fan Lu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Zhejiang, China
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Wu YTY, Ho A, Naduvilath T, Lim C, Carnt N, Keay LJ, Edwards KP, Stapleton F. The risk of vision loss in contact lens wear and following LASIK. Ophthalmic Physiol Opt 2020; 40:241-248. [PMID: 31916275 DOI: 10.1111/opo.12663] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 12/03/2019] [Indexed: 11/28/2022]
Abstract
PURPOSE To compare the risk of vision loss following contemporary laser-assisted in situ keratomileusis (LASIK) with different types and modality of use of contact lenses. METHODS Data from a previously published study were used to derive the incidence of vision loss (≥ 2 line loss of best corrected spectacle acuity) following microbial keratitis for different contact lens types and wearing modality, stratified by duration of lens wear. A literature search on vision loss following LASIK was performed between 2003 and 2019. The prevalence of vision loss at six months post-surgery was captured from clinical trials published after 2003. A proportion meta-analysis was applied to derive the prevalence of vision loss following LASIK. A least-squares fitting of cumulative vision loss (P, /10 000 wearers) over time (t, years) using an exponential model estimated the years of contact lens wear to which the risk of vision loss with LASIK was equivalent. RESULTS Vision loss following LASIK occurred in 66 (95% confidence interval [CI] 34-108) per 10 000 wearers. As a conservative estimate based on the lower confidence interval of the estimated equivalent years of contact lens wear, daily wear contact lenses and extended overnight silicone wear hydrogel contact lens need to be worn for 103 (95% [CI] 103-391) and 25 (95% [CI] 25-79) years respectively, to equal the rate of vision loss equivalent to a one-off LASIK procedure. CONCLUSIONS The risk of vision loss to the individual is low with either contact lens wear or refractive surgery. Contact lens wear does not pose a higher risk of vision loss than LASIK surgery for the most common wear modalities.
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Affiliation(s)
- Yvonne Tzu-Ying Wu
- School of Optometry and Vision Science, The University of New South Wales, Sydney, New South Wales, Australia
| | - Arthur Ho
- School of Optometry and Vision Science, The University of New South Wales, Sydney, New South Wales, Australia.,Vision Cooperative Research Centre, Sydney, New South Wales, Australia.,Brien Holden Vision Institute, Sydney, New South Wales, Australia
| | - Thomas Naduvilath
- School of Optometry and Vision Science, The University of New South Wales, Sydney, New South Wales, Australia.,Brien Holden Vision Institute, Sydney, New South Wales, Australia
| | - Chris Lim
- National University Hospital, Singapore, Sydney, New South Wales, Australia
| | - Nicole Carnt
- School of Optometry and Vision Science, The University of New South Wales, Sydney, New South Wales, Australia.,Brien Holden Vision Institute, Sydney, New South Wales, Australia
| | - Lisa J Keay
- School of Optometry and Vision Science, The University of New South Wales, Sydney, New South Wales, Australia.,Vision Cooperative Research Centre, Sydney, New South Wales, Australia
| | - Katie P Edwards
- Vision Cooperative Research Centre, Sydney, New South Wales, Australia.,Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Fiona Stapleton
- School of Optometry and Vision Science, The University of New South Wales, Sydney, New South Wales, Australia.,Vision Cooperative Research Centre, Sydney, New South Wales, Australia
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Functional Optical Zone After Small-Incision Lenticule Extraction as Stratified by Attempted Correction and Optical Zone. Cornea 2018; 37:1110-1117. [PMID: 29927753 DOI: 10.1097/ico.0000000000001669] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To compare the functional optical zone (OZ) with different levels of myopia and different OZ groups after small-incision lenticule extraction. METHODS This retrospective study included 249 patients (120 men) after small-incision lenticule extraction correction. We grouped participants according to attempted correction [low: spherical equivalent (SE) > -3.0 D; moderate: -6.0 D ≥ SE ≥ -3.0 D; high: SE ≥ -6.0 D] and planned functional optical zone (PFOZ) (OZ-1: PFOZ ≤ 6.3 mm; OZ-2: 6.3 mm < PFOZ ≤ 6.5; OZ-3: PFOZ > 6.5 mm), and we compared the achieved functional optical zone (AFOZ) and total corneal aberration, using Scheimpflug imaging, 1 month postoperatively. Correlations between corneal aberration and AFOZ were analyzed. RESULTS The AFOZ was smaller than the PFOZ in all 3 refraction groups (reduction: low, 0.78 ± 0.72 mm; moderate, 1.22 ± 0.60 mm; and high: 1.49 ± 0.58 mm, P < 0.001). There was no difference in the AFOZ among the 3 OZ groups. Total corneal aberration increased more in the high myopia group (total higher-order aberration, coma, and spherical aberration, P < 0.001), which also correlated with the AFOZ. CONCLUSIONS The discrepancy between the AFOZ and PFOZ increased with greater attempted correction. Attempted correction and AFOZ influence corneal aberration.
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Qian X, Ma T, Shih CC, Heur M, Zhang J, Shung KK, Varma R, Humayun MS, Zhou Q. Ultrasonic Microelastography to Assess Biomechanical Properties of the Cornea. IEEE Trans Biomed Eng 2018; 66:647-655. [PMID: 29993484 DOI: 10.1109/tbme.2018.2853571] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
OBJECTIVE To both qualitatively and quantitatively investigate corneal biomechanical properties through an ultrasonic microelastography imaging system, which is potentially useful in the diagnosis of diseases, such as keratoconus, postrefractive keratectasia, and tracking treatment such as cross-linking surgery. METHODS Our imaging system has a dual-frequency configuration, including a 4.5 MHz ring transducer to push the tissue and a confocally aligned 40 MHz needle transducer to track micron-level displacement. Two-dimensional/three-dimensional acoustic radiation force impulse (ARFI) imaging and Young's modulus in the region of interest were performed on ex vivo porcine corneas that were either cross-linked using formalin solution or preloaded with intraocular pressure (IOPs) from 5 to 30 mmHg. RESULTS The increase of corneal stiffness and the change in cross-linked volume following formalin crosslinking could be precisely observed in the ARFI images and reflected by the reconstructed Young's modulus while the B-mode structural images remained almost unchanged. In addition, the relationship between the stiffness of the cornea and IOPs was investigated among 12 porcine corneas. The corneal stiffness is significantly different at various IOPs and has a tendency to become stiffer with increasing IOP. CONCLUSION Our results demonstrate the principle of using ultrasonic microelastography techniques to image the biomechanical properties of the cornea. Integrating high-resolution ARFI imaging labeled with reconstructed Young's modulus and structural imaging of the cornea can potentially lead to a routinely performed imaging modality in the field of ophthalmology.
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Ma J, Wang Y, Wei P, Jhanji V. Biomechanics and structure of the cornea: implications and association with corneal disorders. Surv Ophthalmol 2018; 63:851-861. [PMID: 29857022 DOI: 10.1016/j.survophthal.2018.05.004] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 05/17/2018] [Accepted: 05/21/2018] [Indexed: 12/14/2022]
Abstract
Recent studies have shown that alterations in corneal biomechanical properties are associated with corneal pathologies, particularly corneal ectasia. Moreover, these alterations may have implications with regard to the outcomes of therapeutic modalities and corneal refractive surgeries. We address corneal anatomy and its relevance to corneal biomechanical characteristics, as well as ocular and systemic conditions associated with changes in corneal biomechanics.
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Affiliation(s)
- Jiaonan Ma
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
| | - Yan Wang
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China; Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Naikai University, Tianjin Medical University, Tianjin, China.
| | - Pinghui Wei
- Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Naikai University, Tianjin Medical University, Tianjin, China
| | - Vishal Jhanji
- UPMC Eye Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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Slade S, Ignacio T, Spector S. Evaluation of a multifunctional femtosecond laser for the creation of laser in situ keratomileusis flaps. J Cataract Refract Surg 2018; 44:280-286. [DOI: 10.1016/j.jcrs.2017.12.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 12/01/2017] [Accepted: 12/06/2017] [Indexed: 11/28/2022]
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Kim JM, Kang MS, Jin KH. Comparison of Anterior Segment Measurements between Scheimpflug Camera and New Module of Optical Coherence Tomography. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2018. [DOI: 10.3341/jkos.2018.59.7.613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Jae Min Kim
- Department of Ophthalmology, Kyung Hee University Hospital, Kyung Hee University School of Medicine, Seoul, Korea
| | - Min Seok Kang
- Department of Ophthalmology, Kyung Hee University Hospital, Kyung Hee University School of Medicine, Seoul, Korea
| | - Kyung Hyun Jin
- Department of Ophthalmology, Kyung Hee University Hospital, Kyung Hee University School of Medicine, Seoul, Korea
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Refractive Errors & Refractive Surgery Preferred Practice Pattern®. Ophthalmology 2018; 125:P1-P104. [DOI: 10.1016/j.ophtha.2017.10.003] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 10/02/2017] [Indexed: 11/19/2022] Open
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Kling S, Hafezi F. Corneal biomechanics - a review. Ophthalmic Physiol Opt 2017; 37:240-252. [PMID: 28125860 DOI: 10.1111/opo.12345] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 11/15/2016] [Indexed: 12/01/2022]
Abstract
PURPOSE In recent years, the interest in corneal biomechanics has strongly increased. The material properties of the cornea determine its shape and therefore play an important role in corneal ectasia and related pathologies. This review addresses the molecular origin of biomechanical properties, models for their description, methods for their characterisation, techniques for their modification, and computational simulation approaches. RECENT FINDINGS Recent research has focused on developing non-contact techniques to measure the biomechanical properties in vivo, on determining structural and molecular abnormalities in pathological corneas, on developing and optimising techniques to reinforce the corneal tissue and on the computational simulation of surgical interventions. SUMMARY A better understanding of corneal biomechanics will help to improve current refractive surgeries, allow an earlier diagnosis of ectatic disorders and a better quantification of treatments aiming at reinforcing the corneal tissue.
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Affiliation(s)
- Sabine Kling
- CABMM, University of Zurich, Zurich, Switzerland
| | - Farhad Hafezi
- CABMM, University of Zurich, Zurich, Switzerland.,ELZA Institute AG Dietikon, Zurich, Switzerland.,USC Roski Eye Institute - Keck School of Medicine, Los Angeles, USA.,Ophthalmology, University of Geneva, Geneva, Switzerland
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Affiliation(s)
- Davin Johnson
- Department of Ophthalmology, CHUM-Notre Dame Hospital, Montreal, Canada
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Shin WB, Jeong HK, Kim MK, Kim HS, Lee JM, Kim CY, Kim JH. Comparison of Central Corneal Thickness Measured by Swept-source Optical Coherence Tomography and Ultrasound Pachymetry. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2017. [DOI: 10.3341/jkos.2017.58.3.276] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Woo Beom Shin
- Siloam Eye Hospital, Seoul, Korea
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
| | - Hyun Kyo Jeong
- Siloam Eye Hospital, Seoul, Korea
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
| | - Min Kyo Kim
- Siloam Eye Hospital, Seoul, Korea
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
| | | | | | - Chan Yun Kim
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
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Hashemi H, Beiranvand A, Yekta A, Asharlous A, Khabazkhoob M. Biomechanical properties of early keratoconus: Suppressed deformation signal wave. Cont Lens Anterior Eye 2016; 40:104-108. [PMID: 27956045 DOI: 10.1016/j.clae.2016.12.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 11/13/2016] [Accepted: 12/06/2016] [Indexed: 11/26/2022]
Abstract
PURPOSE To examine the diagnostic validity of different corneal biomechanical parameters for the detection of early keratoconus METHODS: Sixty-one eyes with a diagnosis of early keratoconus and 61 topographically normal eyes were enrolled in the study. All participants underwent testing with the Ocular Response Analyzer (ORA), and 40 indices from each cornea were included in the analysis. RESULTS The mean (standard deviation: SD) of keratometry and central corneal thickness in keratoconic corneas was 46.9 (2.5) diopter (D) and 473 (31) μm, respectively. Of the 40 evaluated indices, 32 showed a significant difference between the two groups using t-test (p<0.05). According to the results of logistic regression, the indices of height from the lowest to the highest point in peak 2 (H21) and corneal resistance factor (CRF) with R2=0.79 were the best predictors of early keratoconus (p<0.001). H21 ≤190 with a sensitivity and specificity of 87% and 91.8%, respectively, and CRF≤8.6 with sensitivity and specificity of 87% and 85.3%, respectively, yielded an overall diagnostic accuracy of 97.3%. CONCLUSION This study results point to the important role of novel waveform-derived indices measured by ORA, along with conventional biomechanical indices, for the early diagnosis of keratoconus. The best predictors of keratoconus in its early stages are H21 and CRF which showed very high sensitivity and specificity for the detection of early keratoconus.
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Affiliation(s)
- Hassan Hashemi
- Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran
| | - Asghar Beiranvand
- Health and Nutrition Research Center, Lorestan University of Medical Sciences, Khoramabad, Iran
| | - Abbasali Yekta
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Amir Asharlous
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mehdi Khabazkhoob
- Department of Medical Surgical Nursing, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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Liu Q, Zhou YH, Zhang J, Zheng Y, Zhai CB, Liu J. Comparison of corneal flaps created by Wavelight FS200 and Intralase FS60 femtosecond lasers. Int J Ophthalmol 2016; 9:1006-10. [PMID: 27500109 DOI: 10.18240/ijo.2016.07.12] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 08/26/2015] [Indexed: 11/23/2022] Open
Abstract
AIM To assess and compare the morphology of corneal flaps created by the Wavelight FS200 and Intralase FS60 femtosecond lasers in laser in situ keratomileusis (LASIK). METHODS Four hundred eyes of 200 patients were enrolled in this study and divided into Wavelight FS200 groups (200 eyes) and Intralase FS60 groups (200 eyes). Fourier-domain optical coherence tomography (RTVue OCT) was used to measure the corneal flap thickness of 36 specified measurements on each flap one week after surgery. Results were used to analyze the regularity, uniformity and accuracy of the two types of LASIK flaps. RESULTS The mean thickness of corneal flap and central flap was 105.71±4.72 µm and 105.39±4.50 µm in Wavelight FS200 group and 109.78±11.42 µm and 109.15 ±11.59 µm in Intralase FS60 group, respectively. The flaps made with the Wavelight FS200 femtosecond laser were thinner than those created by the Intralase FS60 femtosecond laser (P=0.000). Corneal flaps in the 2 groups were uniform and regular, showing an almost planar configuration. But the Wavelight FS200 group has more predictability and uniformity of flap creation. The mean deviation between achieved and attempted flap thickness was smaller in the Wavelight FS200 group than that in the Intralase FS60 group, which were 5.18±3.71 µm and 8.68±7.42 µm respectively. The deviation of more than 20 µm was 0.2% measurements in Wavelight FS200 group and 8.29% measurements in Intralase FS60 group. CONCLUSION The morphologies of flaps created by Wavelight FS200 are more uniform and thinner than those created by Intralase FS60.
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Affiliation(s)
- Qian Liu
- Ophthalmic Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing 100730, China
| | - Yue-Hua Zhou
- Ophthalmic Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing 100730, China
| | - Jing Zhang
- Ophthalmic Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing 100730, China
| | - Yan Zheng
- Ophthalmic Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing 100730, China
| | - Chang-Bin Zhai
- Ophthalmic Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing 100730, China
| | - Jing Liu
- Ophthalmic Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Lab, Beijing 100730, China
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Measurements of central corneal thickness and endothelial parameters with three different non-contact specular microscopy devices. Int Ophthalmol 2016; 37:229-233. [PMID: 27221264 DOI: 10.1007/s10792-016-0264-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 05/13/2016] [Indexed: 10/21/2022]
Abstract
We aimed to compare the measurements of central corneal thickness (CCT) and endothelial parameters with three different non-contact specular microscopy (SM) devices. Fifteen eyes of 15 healthy individuals (6 males; 9 females) were enrolled in the study. Mean age was 37.93 ± 15.13 years. Endothelial parameters and CCT were measured with Nidek CEM-530, Topcon SP-3000P, and Tomey EM-3000 SM devices by the same physician. Endothelial parameters included endothelial cell count (ECC), maximum, minimum, and average endothelial cell size. and hexagonality ratio. There were no statistically significant differences in ECC, CTT, and average endothelial size (AES) between the devices (p > 0.05). The measurement of maximum endothelial size (MES) was different between Nidek SM and Topcon SM devices (p = 0.001), but there was no difference in MES between Nidek SM and Tomey SM (p = 0.058), and between Topcon SM and Tomey SM (p = 0.081). There was no difference in minimum endothelial size (MinES) between Nidek SM and Topcon SM (p = 0.794); however, there was a significant difference in MinES between Tomey SM and Nidek SM (p < 0.001), and between Tomey SM and Topcon SM (p < 0.001). Comparison of hexagonality ratio showed statistically significant difference between the devices (p < 0.001). No significant differences in the measurements of ECC, CCT, and AES were detected between different SM devices, whereas a statistically significant difference in hexagonality ratio was detected between the devices. These devices should not be used alternatively in the endothelial morphology assessment in patient's follow-up.
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Reliability of Pentacam HR Thickness Maps of the Entire Cornea in Normal, Post-Laser In Situ Keratomileusis, and Keratoconus Eyes. Am J Ophthalmol 2016; 162:74-82.e1. [PMID: 26556008 DOI: 10.1016/j.ajo.2015.11.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 11/03/2015] [Accepted: 11/03/2015] [Indexed: 11/21/2022]
Abstract
PURPOSE To measure the repeatability and reproducibility of Pentacam HR system thickness maps for the entire cornea in normal, post-laser in situ keratomileusis (post-LASIK), and keratoconus (KC) eyes. DESIGN Reliability study. METHODS Sixty normal subjects (60 eyes), 30 post-LASIK subjects (60 eyes), and 14 KC patients (27 eyes) were imaged with the Pentacam HR system by 2 well-trained operators. For pachymetry the cornea was divided into 4 zones: a central zone (2-mm diameter) and concentric pericentral zone (2-5 mm), transitional zone (5-7 mm), and peripheral zone (7-10 mm). The 3 concentric zones were subdivided into 8 sectors. Intraobserver repeatability and interobserver reproducibility of entire corneal thickness maps were tested by the repeatability and reproducibility coefficients, intraclass correlation coefficients, coefficient of variation, and 95% limits of agreement. RESULTS From central to peripheral zones, the precision of corneal thickness measurements became gradually smaller. Central zone repeatability and reproducibility were the best in the normal, post-LASIK, and KC groups. The peripheral superior sectors showed poorer repeatability and reproducibility for all subjects. The intraobserver repeatability and interobserver reproducibility for all zones were ≤19.3 μm, ≤22.1 μm, and ≤20.7 μm, in the normal, post-LASIK, and KC groups, respectively. The intraobserver and interobserver coefficients of variation for all zones were ≤1.3%, ≤1.6%, and ≤1.6% for all 3 groups. CONCLUSIONS Pentacam HR system pachymetry of the entire cornea provided good precision in normal, post-LASIK, and KC corneas. Thickness measurements in the peripheral cornea should be interpreted with caution in abnormal corneas after surgery or with diseases.
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Kim IG, Lee CE, Lee JS, Seo S, Lee KW. Utility of the Swept Source Optical Coherence Tomography for Measurements of Central Corneal Thickness. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2016. [DOI: 10.3341/jkos.2016.57.10.1542] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
| | - Chong Eun Lee
- Department of Ophthalmology, Keimyung University School of Medicine, Daegu, Korea
| | | | - Sam Seo
- Cheil Eye Hospital, Daegu, Korea
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An Y, Kim H, Joo CK. Comparison of Anterior Segment Measurements between Dual and Single Scheimpflug Camera. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2016. [DOI: 10.3341/jkos.2016.57.7.1056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Youngju An
- Catholic Institute of Visual Science, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Hyojin Kim
- Division of Health Science, Baekseok University, Cheonan, Korea
| | - Choun-Ki Joo
- Catholic Institute of Visual Science, College of Medicine, The Catholic University of Korea, Seoul, Korea
- Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, Korea
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Wang Y, Cui C, Li Z, Tao X, Zhang C, Zhang X, Mu G. Corneal ectasia 6.5 months after small-incision lenticule extraction. J Cataract Refract Surg 2015; 41:1100-6. [DOI: 10.1016/j.jcrs.2015.04.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 12/31/2014] [Accepted: 01/01/2015] [Indexed: 10/23/2022]
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Lee MJ, Shin YU, Lim HW, Kang MH, Cho HY, Seong MC. Central Corneal Thickness Measured by Noncontact Specular Microscopy, Dual Rotating Scheimpflug Camera and Ultrasound Pachymetry. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2015. [DOI: 10.3341/jkos.2015.56.10.1520] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Min Jee Lee
- Department of Ophthalmology, Hanyang University Guri Hospital, Hanyang University College of Medicine, Guri, Korea
| | - Yong Un Shin
- Department of Ophthalmology, Hanyang University Guri Hospital, Hanyang University College of Medicine, Guri, Korea
| | - Han Woong Lim
- Department of Ophthalmology, Hanyang University Guri Hospital, Hanyang University College of Medicine, Guri, Korea
| | - Min Ho Kang
- Department of Ophthalmology, Hanyang University Guri Hospital, Hanyang University College of Medicine, Guri, Korea
| | - Hee Yoon Cho
- Department of Ophthalmology, Hanyang University Guri Hospital, Hanyang University College of Medicine, Guri, Korea
| | - Min Cheol Seong
- Department of Ophthalmology, Hanyang University Guri Hospital, Hanyang University College of Medicine, Guri, Korea
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Comparison and Evaluation of Central Corneal Thickness Using 2 New Noncontact Specular Microscopes and Conventional Pachymetry Devices. Cornea 2014; 33:576-81. [DOI: 10.1097/ico.0000000000000113] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Corneal biomechanical properties after LASIK, ReLEx flex, and ReLEx smile by Scheimpflug-based dynamic tonometry. Graefes Arch Clin Exp Ophthalmol 2014; 252:1329-35. [PMID: 24862302 DOI: 10.1007/s00417-014-2667-6] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2013] [Revised: 03/31/2014] [Accepted: 05/06/2014] [Indexed: 10/25/2022] Open
Abstract
PURPOSE To evaluate corneal biomechanical properties after LASIK, ReLEx flex, and the flap-free procedure ReLEx smile by Scheimpflug-based dynamic tonometry (Corvis ST) and non-contact differential tonometry (Ocular Response Analyzer, ORA). METHODS Patients treated for high myopia (-10.5 to -5.5 diopters, spherical equivalent refraction) more than one year previously at Aarhus University Hospital were included. Treatments comprised LASIK (35 eyes), ReLEx flex (31 eyes), and ReLEx smile (29 eyes). A control group included 31 healthy eyes. Cornea-compensated IOP (IOPcc), corneal hysteresis (CH), and corneal resistance factor (CRF) were measured with ORA. Corneal applanation and deformation were registered with Corvis ST during an air-pulse. RESULTS Multiple linear regression analysis showed that CH and CRF were significantly lower after all keratorefractive procedures compared to healthy controls (p < 0.05). No significant differences were observed in CH or CRF between the keratorefractive groups. Corvis ST showed no differences in radius at highest concavity (HC radius), time until first applanation (A1 Time), time until second applanation (A2 Time), and deflection length at highest concavity (HC deflection length) between groups. LASIK treated eyes had significantly shorter time until highest concavity than eyes treated with ReLEx smile (HC Time, p = 0.01). The A1 deflection length was significantly shorter in the keratorefractive groups compared to the healthy controls (p < 0.05). CONCLUSIONS Keratorefrative procedures alter the corneal biomechanical properties with regard to corneal hysteresis and corneal resistant factor. The flap-based LASIK and ReLEx flex and the flap-free ReLEx smile result in similar reduction in corneal biomechanics when evaluated by Corvis ST and ORA.
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Central and midperipheral corneal thickness measured with Scheimpflug imaging and optical coherence tomography. PLoS One 2014; 9:e98316. [PMID: 24854348 PMCID: PMC4031212 DOI: 10.1371/journal.pone.0098316] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Accepted: 04/30/2014] [Indexed: 11/19/2022] Open
Abstract
Purpose To compare corneal thickness measurements using Pentacam (Oculus, Germany), Sirius (CSO, Italy), Galilei (Ziemer, Switzerland), and RTVue-100 OCT (Optovue Inc., USA). Methods Sixty-six eyes of 66 healthy volunteers were enrolled. Three consecutive measurements were performed with each device. The mean value of the three measurements was used for subsequent analysis. Central corneal thickness (CCT), thinnest corneal thickness (TCT), and midperipheral corneal thickness (MPCT; measured at superior, inferior, nasal, and temporal locations with a distance of 1 mm (CT2mm) or 2.5 mm (CT5mm) from the corneal apex) were analyzed. Differences and agreement between measurements were assessed using the repeated-measures analysis of variance (ANOVA) and Bland-Altman analyses, respectively. Results Statistically significant differences (p<0.001) among the four devices were revealed in CCT, TCT and CT2mmmeasurements. The CCT, TCT, and CT2mm values were ranked from the thickest to the thinnest as follows: Galilei>Sirius>Pentacam>RTVue OCT. For these measurements, agreement between measurements by Sirius and Pentacam was good, whereas Galilei overestimated and RTVue underestimated corneal thickness compared to Sirius and Pentacam. As regards CT5mm measurements, Pentacam provided the largest values, whereas RTVue OCT yielded the smallest values. Agreement of the CT5mm measurements was good between the Pentacam, Sirius, moderate between Galilei and the other two Scheimpflug systems, and poor between the RTVue OCT and the remaining devices. Conclusions The Pentacam and Sirius can be used interchangeably for CCT measurements, while the Galilei and RTVue systematically over- and underestimate CCT, respectively. The three Scheimpflug cameras, but not the RTVue, may be used interchangeably for MPCT measurements.
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Wu D, Wang Y, Zhang L, Wei S, Tang X. Corneal biomechanical effects: small-incision lenticule extraction versus femtosecond laser-assisted laser in situ keratomileusis. J Cataract Refract Surg 2014; 40:954-62. [PMID: 24751146 DOI: 10.1016/j.jcrs.2013.07.056] [Citation(s) in RCA: 132] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 07/23/2013] [Accepted: 07/26/2013] [Indexed: 10/25/2022]
Abstract
PURPOSE To compare the biomechanical properties of the cornea after small-incision lenticule extraction (lenticule extraction group) with those after femtosecond laser-assisted laser in situ keratomileusis (femtosecond LASIK group). SETTING Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China. DESIGN Prospective comparative case series. METHODS Corneal hysteresis (CH), the corneal resistance factor (CRF), and 37 other biomechanical waveform parameters were quantitatively assessed with the Ocular Response Analyzer preoperatively and 1 week and 1, 3, and 6 months postoperatively. RESULTS Each group comprised 40 eyes. The decrease in CH and the CRF was statistically significant 1 week postoperatively compared with preoperatively in both groups (P<.0001). However, the CH and CRF values in the lenticule extraction group were significantly higher than those in the femtosecond LASIK group 3 months and 6 months postoperatively (P<.032). The residual stromal thickness index versus the CRF and CH and the planned lenticule thickness versus the change in central corneal thickness were statistically significant in the lenticule extraction group (r = 0.388 to 0.950, P<.018); no significant correlation was found in the femtosecond LASIK group. In the waveform analysis of the lenticule extraction group, 28 of the 37 biomechanical waveform parameters differed significantly between preoperative values and postoperative values (P<.035). CONCLUSIONS Both small-incision lenticule extraction and femtosecond laser-assisted LASIK can cause biomechanical changes in the cornea. However, changes in the cornea's viscoelastic properties were less after lenticule extraction than after LASIK. FINANCIAL DISCLOSURE No author has a financial or proprietary interest in any material or method mentioned.
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Affiliation(s)
- Di Wu
- From Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China
| | - Yan Wang
- From Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China.
| | - Lin Zhang
- From Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China
| | - Shengsheng Wei
- From Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China
| | - Xin Tang
- From Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China
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Yang YS, Koh JW. Utility of the Noncontact Specular Microscopy for Measurements of Central Corneal Thickness. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2014. [DOI: 10.3341/jkos.2014.55.1.59] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Young Seong Yang
- Department of Ophthalmology, Chosun University College of Medicine, Gwangju, Korea
| | - Jae Woong Koh
- Department of Ophthalmology, Chosun University College of Medicine, Gwangju, Korea
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Ozgurhan EB, Kara N, Yildirim A, Bozkurt E, Uslu H, Demirok A. Evaluation of corneal microstructure in keratoconus: a confocal microscopy study. Am J Ophthalmol 2013; 156:885-893.e2. [PMID: 23932262 DOI: 10.1016/j.ajo.2013.05.043] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Revised: 05/29/2013] [Accepted: 05/31/2013] [Indexed: 10/26/2022]
Abstract
PURPOSE To compare the corneal microstructure in patients with manifest keratoconus (KCN), subclinical KCN, and topographically normal relatives of patients with KCN and in healthy controls. DESIGN Prospective and cross-sectional study. METHODS We enrolled 145 subjects in the study. The participants were divided into 4 groups, based on clinical and topographical evaluation: the manifest KCN group (n = 30), the subclinical KCN group (n = 32), the KCN relatives group (n = 53), and the control group (n = 30). Corneal microstructure was assessed by corneal in vivo confocal microscopy in all of the individuals. Mean outcome measures were basal epithelial cell density, endothelial cell density, anterior keratocyte density, posterior keratocyte density, sub-basal nerve density, sub-basal nerve diameter, and stromal nerve diameter. RESULTS The mean basal epithelial cell density, endothelial cell density, and sub-basal nerve diameter were not significantly different among the 4 groups (P = 0.057, P = 0.592, and P = 0.393, respectively). The mean anterior and posterior stromal keratocyte densities were significantly lower in the manifest group, in the subclinical group, and in the relatives group when compared with the control group (for both parameters; P < 0.001, P < 0.001, and P< 0.001, respectively). The mean stromal nerve diameter in the manifest group, subclinical group, and relatives group was significantly higher than in the control group (P = 0.001, P = 0.049, and P = 0.004, respectively). CONCLUSION The anterior and posterior stromal keratocyte densities were statistically lower and stromal nerve diameter was statistically higher in patients with manifest KCN, subclinical KCN, and topographically normal KCN relatives compared with controls. Confocal microscopy may be useful for the determination of early corneal microstructural changes before manifestation of typical or subtle topographic signs.
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Huang J, Ding X, Savini G, Pan C, Feng Y, Cheng D, Hua Y, Hu X, Wang Q. A Comparison between Scheimpflug Imaging and Optical Coherence Tomography in Measuring Corneal Thickness. Ophthalmology 2013; 120:1951-8. [DOI: 10.1016/j.ophtha.2013.02.022] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 02/17/2013] [Accepted: 02/18/2013] [Indexed: 11/16/2022] Open
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Corneal collagen cross-linking in the stabilization of PRK, LASIK, thermal keratoplasty, and orthokeratology. Curr Opin Ophthalmol 2013; 24:291-5. [PMID: 23736897 DOI: 10.1097/icu.0b013e3283622d51] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
PURPOSE OF REVIEW To describe the use of corneal collagen cross-linking (CXL) and its efficacy in the stabilization of keratorefractive procedures, including PRK, laser in-situ keratomileusis (LASIK), thermal keratoplasty, and orthokeratology. RECENT FINDINGS Since its introduction, CXL has quickly gained interest in the treatment of ectactic disorders due to its ability to increase the biomechanical stability of the cornea. In its earliest use, it has shown to be effective in the treatment of both keratoconus and post-LASIK ectasia. More recent studies of CXL in combination with keratorefractive procedures have shown varying degrees of success. SUMMARY CXL with PRK has shown to be effective in slowing or halting the progression of keratoconus, pellucid marginal degeneration, and post-LASIK ectasia, in addition to potentially decreasing or delaying the need for penetrating keratoplasty. Several small case series have also demonstrated improved stability and efficacy of PRK and LASIK when combined with CXL, as well as a potentially decreased risk of postprocedure ectasia. In conjunction with thermokeratoplasty and orthokeratology, CXL has shown improved but only temporary results in the treatment of keratoconus. Future studies are needed to determine the efficacy and long-term stability of CXL in combination with keratorefractive procedures, as well as to address possible complications.
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Biomechanical Evaluation of Cornea in Topographically Normal Relatives of Patients With Keratoconus. Cornea 2013; 32:262-6. [DOI: 10.1097/ico.0b013e3182490924] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Enhanced Screening for Ectasia Susceptibility Among Refractive Candidates: The Role of Corneal Tomography and Biomechanics. CURRENT OPHTHALMOLOGY REPORTS 2013. [DOI: 10.1007/s40135-012-0003-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Abstract
PURPOSE To assess the repeatability and reproducibility of central corneal thickness (CCT) measurements by high-resolution rotating Scheimpflug imaging (Pentacam, Oculus) and Fourier-domain optical coherence tomography (RTvue-100, Optovue) after laser in situ keratomileusis (LASIK) and to compare the agreement with ultrasound pachymetry (USP). METHODS Forty-seven eyes of 47 patients after LASIK were included in the study. The first examiner took two successive Pentacam and RTvue CCT measurements, and this was repeated once again by the second examiner to assess intraobserver and interobserver repeatability and reproducibility. After performing non-contact examinations, the corneas were measured by USP to compare the level of agreement among the three devices. RESULTS All Pentacamcenter, Pentacamapex, Pentacamthinnest, and RTvue CCT measurements demonstrated high intraobserver repeatability, with respective precision (1.96 within-subject standard deviation) and intraclass correlation coefficients of 7.52, 7.43, 7.55, and 3.81 μm and 0.985, 0.986, 0.986, and 0.997; interobserver repeatability results were similar. All coefficients of variation were low: <1% for all measures. Compared with Pentacam and USP measurements, the RTvue measurement significantly underestimated CCT by a mean of 10.52 to 15.28 μm (p < 0.001) and 9.17 μm (p < 0.001), respectively. The agreement of USP with Pentacam and RTvue by Bland-Altman analysis spanned over 30 μm. The agreement of Pentacam with RTvue spanned approximate 20 μm. CONCLUSIONS Both Pentacam imaging and RTvue Fourier-domain optical coherence tomography provide reliable and interchangeable measurement of CCT in post-LASIK corneas. However, they cannot be considered to be clinically interchangeable with USP.
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Chen S, Huang J, Wen D, Chen W, Huang D, Wang Q. Measurement of central corneal thickness by high-resolution Scheimpflug imaging, Fourier-domain optical coherence tomography and ultrasound pachymetry. Acta Ophthalmol 2012; 90:449-55. [PMID: 20560892 DOI: 10.1111/j.1755-3768.2010.01947.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE To compare the repeatability and reproducibility of central corneal thickness (CCT) measurements by high-resolution (HR) rotating Scheimpflug imaging and Fourier-domain optical coherence tomography (FD-OCT). CCT measurements were compared to those determined by ultrasound pachymetry (UP). METHODS In 35 healthy eyes, intra-observer repeatability for HR Scheimpflug (Pentacam) and FD-OCT (RTVue) systems was determined in consecutive images taken by an observer in the shortest time possible. Imaging was repeated again by a second observer to evaluate inter-observer reproducibility. The CCT measurements were compared among Scheimpflug, FD-OCT and UP images. RESULTS Mean coefficients of repeatability were 0.48% for Scheimpflug and 0.26% for FD-OCT. For Scheimpflug, the coefficient of inter-operator reproducibility was 0.87%. For FD-OCT, the coefficient of inter-operator reproducibility was 0.45%. The CCT measurements by Scheimpflug, OCT and UP images were (mean ± standard deviation) 521.7 ± 27.6 μm, 510.8 ± 28.6 μm and 516.5 ± 27.6 μm, respectively. The differences between instruments were statistically significant. The 95% limits of agreement in CCT were -0.7 to 22.5 μm for Pentacam-OCT, -13.4 to 24.0 μm for Pentacam-UP and -26.7 to 15.4 μm for OCT-UP. There was a high degree of correlation between CCT measured by all 3 methods. CONCLUSION Noncontact measurements of CCT with HR Scheimpflug and FD-OCT systems yielded excellent repeatability and reproducibility and can be used interchangeably. Although both devices were comparable with UP; in clinical practice, the measurements acquired by optical modalities are not directly interchangeable with UP measurements.
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Affiliation(s)
- Shihao Chen
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China
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Celik UH, Alagöz N, Yildirim Y, Agca A, Marshall J, Demirok A, Yilmaz OF. Accelerated corneal crosslinking concurrent with laser in situ keratomileusis. J Cataract Refract Surg 2012; 38:1424-31. [DOI: 10.1016/j.jcrs.2012.03.034] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2012] [Revised: 03/20/2012] [Accepted: 03/24/2012] [Indexed: 01/13/2023]
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Ogbuehi KC, Osuagwu UL. Repeatability and interobserver reproducibility of Artemis-2 high-frequency ultrasound in determination of human corneal thickness. Clin Ophthalmol 2012; 6:761-9. [PMID: 22693418 PMCID: PMC3367432 DOI: 10.2147/opth.s31690] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Background The purpose of this study was to assess the repeatability and limits of agreement of corneal thickness values measured by a high-frequency ultrasound (Artemis-2), hand-held ultrasound pachymeter (DGH-500) and a specular microscope (SP-3000P). Methods Central corneal thickness (CCT) was analyzed in this prospective randomized study that included 32 patients (18 men and 14 women) aged 21–24 years. Measurements were obtained in two sessions, one week apart, by two examiners with three devices in a randomized order. Nine measurements were taken (three with each device) on one randomly selected eye of each patient in each measurement session. The coefficient of repeatability and interobserver reproducibility for the values of each method were calculated. The limits of agreement between techniques were also evaluated. Results There were no significant differences in CCT values between sessions for each of the three devices (P > 0.05). The repeatability coefficients for the Artemis-2 (±8 μm/±9 μm) were superior to those of the SP-3000P (±9 μm/±11 μm) and DGH 500 (±12 μm/±12 μm) in session 1/session 2 respectively, while the interobserver reproducibility index (differences between session 1 and session 2) was superior for the SP-3000P (±17 μm) with respect to DHG-500 (±29 μm) and the Artemis-2 (±31 μm). In session 1 and session 2, the limits of agreement between the techniques were 35 μm to −31 μm and 34 to −20 μm, respectively, for DGH-500 versus Artemis-2, 73 μm to 3 μm and 60 μm to 9 μm for Artemis-2 versus SP-3000P, and 58 μm to 22 μm and 72 μm to 10 μm for DGH-500 versus SP-3000P comparisons. The DGH-500 and Artemis-2 gave similar values (P > 0.05) in both sessions, but both (Artemis-2 and DGH-500) values were significantly greater than that of the SP-3000P (P < 0.05) in both sessions. Conclusion Repeatability was comparably good for the three techniques. However, interobserver reproducibility was approximately twice as good with the SP-3000P compared with the other two devices. The Artemis-2 CCT values consistently agreed with the DGH-500 and less so with the SP-3000P. The Artemis-2 provided CCT values that were, on average, 38 μm and 34 μm greater than that of the SP-3000P in session 1 and session 2, respectively.
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Affiliation(s)
- Kelechi C Ogbuehi
- Outpatient Clinic, Department of Optometry, King Saud University, Riyadh, Kingdom of Saudi Arabia
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Abstract
ABSTRACT
Purpose
To evaluate the accuracy of a new objective method for the detection of ectasia susceptible eyes.
Methods
One hundred and eighty-three elevation and placido topographies were retrospectively evaluated by one experimented refractive surgeon and classified as ‘normal’ or ‘at risk for LASIK’. An objective automated system built on the combination of topography and tomography data in a discriminant function was also used to classify the corneas. The concordance between the objective and the subjective classification was evaluated and the usefulness of the objective scoring system was assessed by receiver operating characteristic (ROC) curve analysis.
Results
The mean age of the studied group was 37 ± 8 years old. One hundred and fifty-nine eyes were subjectively classified as ‘normal’ and 24 as ‘At risk for LASIK’. The scoring system correctly classified 153 eyes as ‘normal’ and 22 eyes as ‘at risk for LASIK’. Six eyes were wrongly detected as ‘at risk’ by the automated system (false-positive) and two eyes were wrongly classified as ‘normal’ (false-negative). The sensitivity and specificity of the automated system were 92 and 96% respectively.
Conclusion
An automated system built on the combination of topography and tomography parameters can help in creating a sensitive and specific artificial intelligence for the detection of corneas at risk for refractive surgery.
How to cite this article
Saad A, Gatinel D. Validation of a New Scoring System for the Detection of Early Forme of Keratoconus. Int J Kerat Ect Cor Dis 2012;1(2):100-108.
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Said A, Hamade IH, Tabbara KF. Late onset corneal ectasia after LASIK surgery. Saudi J Ophthalmol 2011; 25:225-30. [PMID: 23960929 DOI: 10.1016/j.sjopt.2011.05.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 05/06/2011] [Accepted: 05/06/2011] [Indexed: 11/28/2022] Open
Abstract
PURPOSE To report late onset corneal ectasia following myopic LASIK. METHODS A retrospective cohort case series. Nineteen patients with late onset corneal ectasia following LASIK procedure were examined at The Eye Center, Riyadh, Saudi Arabia. Patients underwent LASIK for myopia with spherical equivalent ranging from -1.4 to -13.75 diopters. Age and gender, history of systemic or local diseases, and time of onset of corneal ectasia were recorded. Eye examination and corneal topographical analyses were done before and after LASIK surgery. RESULTS Nineteen patients (29 eyes) with late onset corneal ectasia were identified from 1998 to 2008 in 13 male and six female patients. The mean follow-up period was 108 ± 23 months (range 72-144 months). No patient had pre-operative identifiable risk factors for corneal ectasia and the mean time of onset was 57 ± 24 months (range 24-120 months after LASIK). The pre-operative values included mean central pachymetry 553 ± 25 μm, mean keratometry reading of 42.9 ± 1.5 diopters, average oblique cylinder of 1.4 ± 1.2 diopters, posterior surface elevation of 26 ± 2.1 diopters, corneal flap thickness of 160 μm, mean spherical equivalent of -5.6 ± 3.6 diopters, and calculated residual corneal stromal bed thickness was 288 ± 35 μm. Three (5 eyes) patients developed ectasia after pregnancy. Three (4 eyes) patients developed corneal ectasia following severe adenoviral keratoconjunctivitis and had positive PCR for adenovirus type 8. CONCLUSIONS Corneal ectasia may develop many years after LASIK surgery and symptoms could go undetected for some time. Pregnancy and adenoviral keratoconjunctivitis occurred post-operatively in six patients.
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Affiliation(s)
- Ashraf Said
- The Eye Center and the Eye Foundation for Research in Ophthalmology, Riyadh, Saudi Arabia
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Corneal biomechanical properties in normal, forme fruste keratoconus, and manifest keratoconus after statistical correction for potentially confounding factors. Cornea 2011; 30:516-23. [PMID: 21045653 DOI: 10.1097/ico.0b013e3181f0579e] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To evaluate the difference in corneal biomechanical properties, after controlling for potentially confounding factors, along the spectrum of keratoconic disease as measured by the keratoconus severity score. METHODS The corneal biomechanical properties of 73 keratoconic (KCN) eyes of 54 patients, 42 forme fruste keratoconic (FFKCN) eyes of 32 patients, and 115 healthy eyes of 115 age- and sex-matched patients were reviewed retrospectively. The main outcome measures were corneal hysteresis (CH) and corneal resistance factor (CRF). RESULTS In the normal group, the mean CH was 11.0 ± 1.4 mm Hg and mean CRF was 11.1 ± 1.6 mm Hg. The FFKCN mean CH was 8.8 ± 1.4 mm Hg and mean CRF was 8.6 ± 1.3 mm Hg. The KCN mean CH was 7.9 ± 1.3 mm Hg and mean CRF was 7.3 ± 1.4 mm Hg. There were statistically significant differences in the mean CH and CRF in the normal group compared with the FFKCN and the KCN groups (P < 0.001) after statistically controlling for differences in central corneal thickness, age, and sex. CONCLUSIONS There is a significant difference in the mean CH and CRF between normal and FFKCN corneas after controlling for differences in age, sex, and central corneal thickness. However, there is a significant overlap in the distribution of CH and CRF values among all groups. The biomechanical parameters CH and CRF cannot be used alone but may be a useful clinical adjunct to other diagnostic tools, such as corneal tomography, in distinguishing normal from subclinical keratoconic corneas.
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Bamashmus M, Saleh MF, Abdulrahman M, Al-Kershy N. Reasons for not performing LASIK in refractive surgery candidates in Yemen. Eur J Ophthalmol 2010; 20:858-64. [PMID: 20383849 DOI: 10.1177/112067211002000508] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PURPOSE To determine and analyze the reasons that laser in situ keratomileusis (LASIK) was not performed in patients who requested refractive surgical correction of their refractive errors. METHODS A retrospective observational study was performed in Yemen Magrabi Hospital between June 2005 and October 2006; the case records of 1596 new consecutive patients who presented for refractive surgery at our refractive surgery unit were reviewed. Data on the ocular status, refractive problems, and investigations performed were analyzed. The reasons for not performing LASIK in the cases that were rejected were recorded and analyzed. RESULTS A total of 1191 patients (74.6%) were advised to have LASIK of the 1596 patients examined. LASIK was not advised in 405 patients (25.4%). The most common reasons for rejecting LASIK were suboptimal central corneal thickness (25.9%), high myopia >-11.00 D (17.0%), keratoconus (15.5%), cataract (11.4%), and suspicious corneal topography (forme fruste keratoconus) (9.4%). CONCLUSIONS Patients who request refractive surgery have a variety of problems and attention must be given to these patients. Suboptimal corneal thickness, high amount of refractive error, and keratoconus were found to be the leading causes of not performing LASIK in Yemeni patients.
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Affiliation(s)
- Mahfouth Bamashmus
- Eye Department, Faculty of Medicine and Health Sciences, Sana'a University, Magrabi Eye Hospital, Sana'a, Republic of Yemen.
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Javadi MA, Feizi S. Deep anterior lamellar keratoplasty using the big-bubble technique for keratectasia after laser in situ keratomileusis. J Cataract Refract Surg 2010; 36:1156-60. [DOI: 10.1016/j.jcrs.2010.01.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Revised: 12/25/2009] [Accepted: 01/14/2010] [Indexed: 11/15/2022]
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Saad A, Gatinel D. Bilateral corneal ectasia after laser in situ keratomileusis in patient with isolated difference in central corneal thickness between eyes. J Cataract Refract Surg 2010; 36:1033-5. [DOI: 10.1016/j.jcrs.2010.03.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2009] [Accepted: 12/08/2009] [Indexed: 10/19/2022]
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Sharma N, Sachdev R, Jindal A, Titiyal JS. Acute Hydrops in Keratectasia After Radial Keratotomy. Eye Contact Lens 2010; 36:185-7. [DOI: 10.1097/icl.0b013e3181da23ba] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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New INTACS SK Implantation in Patients With Post–Laser In Situ Keratomileusis Corneal Ectasia. Cornea 2010; 29:214-6. [DOI: 10.1097/ico.0b013e3181a26b72] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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