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Sedaghat MR, Momeni-Moghaddam H, Yekta AA, Maddah N, Roberts CJ, Savardashtaki M. Early elastic and viscoelastic corneal biomechanical changes after photorefractive keratectomy and small incision lenticule extraction. Int Ophthalmol 2024; 44:302. [PMID: 38954134 DOI: 10.1007/s10792-024-03169-8] [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: 11/19/2023] [Accepted: 06/15/2024] [Indexed: 07/04/2024]
Abstract
PURPOSE To compare early changes in the corneal biomechanical parameters after photorefractive keratectomy (PRK) and small incision lenticule extraction (SMILE) and their correlations with corneal shape parameters. METHODS One hundred twenty four eyes received myopic PRK and SMILE for similar amounts of myopia. Corneal tomography with Pentacam HR, biomechanical parameters using Corvis ST, and Ocular Response Analyzer (ORA) were evaluated before and 2 weeks after surgery. The change in each parameter was compared between groups, while the difference in central corneal thickness and cornea-compensated intraocular pressure measured before and after surgery were considered as covariates. RESULTS A significant reduction was seen in the corneal stiffness parameter at first applanation, and an increase in deformation amplitude ratio (DAR), and integrated inverse radius (IIR) in both groups after surgery (p < 0.001) Changes in DAR, and IIR were significantly greater in the SMILE than in the PRK group (p < 0.001) Corneal hysteresis (CH) and corneal resistance factor (CRF) decreased in both SMILE and PRK groups after surgery, (p < 0.001) with no statistically significant difference between groups (p > 0.05) Among new Corvis ST parameters, DAR showed a significant correlation with changes in Ambrosio relational thickness in both groups (p < 0.05). CONCLUSIONS Both techniques caused significant changes in corneal biomechanics in the early postoperative period, with greater elastic changes in the SMILE group compared to the PRK group, likely due to lower tension in the SMILE cap and thinner residual stromal bed in SMILE. There were no differences in viscoelastic changes between them, so the lower CH may reflect the volume of tissue removed.
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Affiliation(s)
| | - Hamed Momeni-Moghaddam
- Rehabilitation Sciences Research Center, Zahedan University of Medical Sciences, Zahedan, Iran.
| | - Abbas-Ali Yekta
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Nasim Maddah
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Cynthia J Roberts
- Department of Ophthalmology and Visual Sciences; and Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Maryam Savardashtaki
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
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Lin MY, Tan HY, Chang CK. Myopic Regression after FS-LASIK and SMILE. Cornea 2024:00003226-990000000-00563. [PMID: 38780430 DOI: 10.1097/ico.0000000000003573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Accepted: 04/13/2024] [Indexed: 05/25/2024]
Abstract
PURPOSE To compare the degree of myopic regression after myopia correction with either femtosecond laser-assisted in situ keratomileusis (FS-LASIK) or small-incision lenticule extraction (SMILE) over 18 months. METHODS Patients undergoing FS-LASIK or SMILE surgery for myopia correction were retrospectively recruited. The propensity scores were used to match patients by age and preoperative manifest spherical equivalent (SEQ) from these 2 groups. Myopic regression was analyzed using the Cox proportional hazard model. RESULTS A total of 416 eyes of 416 patients undergoing FS-LASIK and 416 eyes of 416 patients undergoing SMILE were matched. Using 1-month SEQ as baseline, the SEQ regression values after FS-LASIK were 0D, -0.17 ± 0.69D, -0.24 ± 0.65D, -0.31 ± 0.65D, -0.32 ± 0.63D, and -0.33 ± 0.62D and the SEQ regression values after SMILE were 0D, -0.07 ± 0.75D, -0.18 ± 0.77D, -0.23 ± 0.82 D, -0.21 ± 0.77D, and -0.24 ± 0.68D at 1, 3, 6, 9, 12, and 18 months, respectively. The Cox proportional hazard model showed that preoperative manifest SEQ (P = 0.021) and designed optical zone (P = 0.048) are significant predictors. The selected surgical procedure had no significant effect on predicting myopic regression (P = 0.470). The cumulative survival rates of myopic regression were 54.74% and 42.10% in the FS-LASIK group and 58.66% and 43.83% in the SMILE group, at 12 and 18 months, respectively (log-rank test, P = 0.11). CONCLUSIONS After matching based on age and preoperative manifest SEQ, we found that higher myopia and a smaller optical zone contribute significantly to the development of myopic regression after undergoing FS-LASIK or SMILE surgery at 18 months. The selected surgical procedure, however, does not affect the likelihood of myopic regression.
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Affiliation(s)
- Meng-Yin Lin
- Department of Ophthalmology, Shuang Ho Hospital, Taipei Medical School of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Hsin-Yuan Tan
- Department of Ophthalmology, Chang Gung Memorial Hospital, Linko, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Chao-Kai Chang
- Nobel Eye Institute, Taipei, Taiwan; and
- Department of Optometry, Da-Yeh University, Changhua County, Taiwan
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Hira S, Klein Heffel K, Mehmood F, Sehgal K, Felix De Farias Santos AC, Steuernagel Del Valle G. Comparison of refractive surgeries (SMILE, LASIK, and PRK) with and without corneal crosslinking: systematic review and meta-analysis. J Cataract Refract Surg 2024; 50:523-533. [PMID: 38288954 DOI: 10.1097/j.jcrs.0000000000001405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 01/22/2024] [Indexed: 04/24/2024]
Abstract
Corneal crosslinking (CXL) is used for treating keratoconus and post-laser in situ keratomileusis ectasia. However, refractive surgery is not usually performed with prophylactic CXL. Therefore, we performed a meta-analysis comparing outcomes of refractive surgeries with vs without prophylactic CXL. We systematically searched databases for studies comparing refractive surgeries for myopic correction with vs without prophylactic corneal crosslinking. Review Manager 5.4.1 was used to perform statistical analysis. We included 2820 eyes from 28 studies. Compared with refractive surgery alone, surgery with prophylactic CXL resulted in decreased central corneal thickness, corrected distance visual acuity logMAR, and safety and efficacy indices. There were no significant differences in postoperative uncorrected distance visual acuity of 20/20 or better at ≥12 months and other visual outcomes among both groups. More randomized controlled trials with standard crosslinking protocols are needed to analyze the prophylactic use of crosslinking with refractive surgeries.
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Affiliation(s)
- Sara Hira
- From the FMH College of Medicine & Dentistry, Lahore, Pakistan (Hira); Federal University of Pelotas, Pelotas, Brazil (Klein Heffel); Department of Ophthalmology, Fatima Memorial Hospital, Lahore, Pakistan (Mehmood); Teerthanker Mahaveer University, Moradabad, UP, India (Sehgal); City University of São Paulo, São Paulo, Brazil (Felix De Farias Santos); University of Iowa, Iowa City, Iowa (Steuernagel Del Valle)
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Cao H, Jhanji V, Wang Y. Relationship between postoperative residual refractive error and preoperative corneal stiffness in small-incision lenticule extraction. J Cataract Refract Surg 2023; 49:942-948. [PMID: 37379041 DOI: 10.1097/j.jcrs.0000000000001250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 06/21/2023] [Indexed: 06/29/2023]
Abstract
PURPOSE To explore the relationship between postoperative residual refractive error and preoperative corneal stiffness after small-incision lenticule extraction (SMILE). SETTING Hospital clinic. DESIGN Retrospective cohort study. METHODS Corneal stiffness was evaluated using the stress-strain index (SSI). Associations between postoperative spherical equivalent (SE) and corneal stiffness were determined using longitudinal regression analysis after adjustment for sex, age, preoperative SE, and other variables. The cohort was divided into halves to compare risk ratios for residual refraction in corneas with different SSI values. Low SSI values were defined as having less-stiff corneas and others as having stiffer corneas. RESULTS 287 patients (287 eyes) were included. Greater undercorrection was found in less-stiff corneas across all follow-up timepoints (less-stiff corneas: 1 day: -0.36 ± 0.45 diopters [D], 1 month: -0.22 ± 0.36 D, and 3 months: -0.13 ± 0.15 D; stiffer corneas: -0.22 ± 0.37 D, -0.14 ± 0.35 D, and -0.05 ± 0.11 D, respectively). Postoperative refraction exhibited a mean 0.05 D undercorrection for every 0.1-unit decrease in the SSI after adjustment for variables. The SSI accounted for nearly 10% of the variance in refractive outcomes. Less-stiff corneas increased the risk ratio of postoperative absolute SE >0 D and ≥0.25 D by 2.242 (95% CI, 1.334-3.768) and 3.023 (95% CI, 1.466-6.233), respectively, compared with stiffer corneas. CONCLUSIONS Postoperative residual refractive error was associated with preoperative corneal stiffness. Patients with less-stiff corneas had a 2- to 3-fold increased risk of residual refractive error after SMILE. Preoperative analysis of corneal stiffness can help modify nomogram algorithms of surgery and improve the predictability of refractive outcomes.
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Affiliation(s)
- Huazheng Cao
- From the School of Medicine, Nankai University, Tianjin, China (Cao); Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania (Jhanji); Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Tianjin, China (Wang); Nankai Eye Institute, Nankai University, Tianjin, China (Wang)
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Pérez-Corral J, Cardona G, Piñero DP, Barroso D, Armadans L. Short- and mid-term changes in CORVIS ST parameters in successful, adult orthokeratology patients. Clin Exp Optom 2023; 106:726-733. [PMID: 36375143 DOI: 10.1080/08164622.2022.2140031] [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: 03/27/2022] [Revised: 07/12/2022] [Accepted: 10/20/2022] [Indexed: 11/16/2022] Open
Abstract
CLINICAL RELEVANCE The changes in various biomechanical and tomographic characteristics of the cornea associated with orthokeratology may allow us to identify potential mid- and long-term structural alterations, resulting in a better understanding of the governing mechanisms of this procedure and in its optimisation. BACKGROUND The study aimed at describing short and mid-term changes in CORVIS ST® parameters and indices in orthokeratology (ortho-k), and their diurnal variations. METHODS A prospective observational study was designed in which several CORVIS ST® parameters of 75 new adult participants successfully fitted with overnight ortho-k Seefree® (Conóptica - Hecht Contactlinsen) contact lenses were explored. Measurements were conducted in baseline (BL) conditions and in the morning and evening at the one-night (1 NM/1NT), one-week (1WM/1 WT) and 3-month (3 MM/3MT) follow-up visits. RESULTS Statistically significant differences were found in DARatio_2 mm, IntRad, ARTh, CBI and TBI following overnight ortho-k, when compared with BL values, with most values reaching stability at 1WM or reverting to BL values at 3 MM. The ARTh and CBI parameters showed some of the most significant temporal variations (both p < 0.001), probably reflecting the encountered differences in central corneal thickness between BL and 1WM (p = 0.010) and between BL and 3 MM (p = 0.016). In general, corneal rigidity was higher in the morning at all follow-up visits, and decreased during the day. No statistically significant changes in adjusted intraocular pressure values were found. CONCLUSION Ortho-k in adults may be considered a safe procedure in terms of short and mid-term changes in CORVIS ST® parameters. The observed alterations in most of the parameters provided by the Corvis ST® probably responded to the well-described changes in corneal pachymetry and tomography, rather than to actual alterations in corneal rigidity.
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Affiliation(s)
- Joan Pérez-Corral
- School of Optics and Optometry, Department of Optics and Optometry, Universitat Politècnica de Catalunya, Terrassa, Spain
| | - Genis Cardona
- School of Optics and Optometry, Department of Optics and Optometry, Universitat Politècnica de Catalunya, Terrassa, Spain
| | - David P Piñero
- Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain
| | - David Barroso
- School of Optics and Optometry, Department of Optics and Optometry, Universitat Politècnica de Catalunya, Terrassa, Spain
| | - Laura Armadans
- School of Optics and Optometry, Department of Optics and Optometry, Universitat Politècnica de Catalunya, Terrassa, Spain
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Efficacy and safety of loteprednol etabonate versus fluorometholone in the treatment of patients after corneal refractive surgery: a meta-analysis. Int Ophthalmol 2023:10.1007/s10792-023-02646-w. [PMID: 36869982 DOI: 10.1007/s10792-023-02646-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Accepted: 02/19/2023] [Indexed: 03/05/2023]
Abstract
PURPOSE To perform a systematic evaluation of the efficacy and safety of loteprednol etabonate (LE) 0.5% versus fluorometholone (FML) 0.1% for treating patients after corneal refractive surgery with the aim of providing an evidence-based rationale for clinical drug selection. METHODS Electronic databases (PubMed, EMBASE, Cochrane Library, Web of Science, WanFang, and CNKI) were searched (from inception to December 2021) for comparative clinical studies that evaluated LE versus FML treatment for post-corneal refractive surgery patients. Meta-analysis was performed using the RevMan 5.3 software. The pooled risk ratio (RR) and weighted mean difference (WMD) with corresponding 95% confidence interval (CI) were calculated. RESULTS Nine studies with a total sample size of 2677 eyes were included in this analysis. FML 0.1% and LE 0.5% produced a similar incidence of corneal haze within 6 months after surgery (P = 0.13 at 1 month, P = 0.66 at 3 months, and P = 0.12 at 6 months). There was no statistically significant difference between the two groups in terms of the mean logMAR postoperative uncorrected distance visual acuity (WMD: - 0.00; 95% CI: - 0.01 to 0.00; P = 0.29) and spherical equivalent (WMD: 0.01; 95% CI: - 0.01 to 0.03; P = 0.35). LE 0.5% appears to have a higher tendency to reduce the incidence of ocular hypertension compared FML 0.1%, but there was no statistical significance (RR: 0.63; 95% CI: 0.27 to 1.50; P = 0.30). CONCLUSION This meta-analysis demonstrated that LE 0.5% and FML 0.1% had comparable efficacy in preventing corneal haze and corticosteroid-induced ocular hypertension, with no difference in visual acuity in patients after corneal refractive surgery.
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In Vivo Evaluation of the Effects of SMILE with Different Amounts of Stromal Ablation on Corneal Biomechanics by Optical Coherence Elastography. Diagnostics (Basel) 2022; 13:diagnostics13010030. [PMID: 36611322 PMCID: PMC9818797 DOI: 10.3390/diagnostics13010030] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 12/18/2022] [Accepted: 12/18/2022] [Indexed: 12/24/2022] Open
Abstract
This work aims to depth-resolved quantitatively analyze the effect of different stromal ablation amounts on the corneal biomechanical properties during small incision lenticule extraction (SMILE) using optical coherence elastography (OCE). A 4.5-MHz ultrasonic transducer was used to excite elastic waves in the corneal tissue. The OCE system combined with the antisymmetric Lamb wave model was employed to achieve a high-resolution, high-sensitivity, and depth-resolved quantitative detection of the corneal Young's modulus. Eighteen rabbits were randomly divided into three groups; each group had six rabbits. The first and second groups underwent -3D and -6D SMILE surgeries, and the third group was the control group, respectively. Young's modulus of the corneal cap and residual stromal bed (RSB) were both increased after SMILE, which shared the stress under intraocular pressure (IOP). Furthermore, the Young's modulus of both the corneal cap and RSB after 3D SMILE group were significantly lower than that in the -6D group, which indicated that the increases in the post-operative corneal Young's modulus were positively correlated with the amount of stromal ablation. The OCE system for quantitative spatial characterization of corneal biomechanical properties can provide useful information on the extent of safe ablation for SMILE procedures.
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Zarei-Ghanavati S, Jafarpour S, Hassanzadeh S, Bakhtiari E, Daraee G, Monadi SD, Ziaei M. Changes in Corneal Biomechanical Properties After Small-Incision Lenticule Extraction and Photorefractive Keratectomy, Using a Noncontact Tonometer. Cornea 2022; 41:886-893. [PMID: 34690272 DOI: 10.1097/ico.0000000000002888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 08/14/2021] [Indexed: 10/20/2022]
Abstract
PURPOSE The aim of this study was to evaluate and compare early corneal biomechanical changes after small-incision lenticule extraction (SMILE) and photorefractive keratectomy (PRK). METHODS The study comprised 74 patients eligible for refractive surgery, equally allocated to PRK (37 patients) and SMILE (37 patients). Corneal biomechanical properties were recorded and compared between the 2 groups at preoperatively and 3 months after surgery using a dynamic ultra-high-speed Scheimpflug camera equipped with a noncontact tonometer. RESULTS Both procedures significantly affected corneal biomechanical properties at 3 months after surgery. Patients in the PRK group showed significantly better results for deformation amplitude ratio (DA ratio) ( P = 0.03), maximum inverse radius (InvRadMax) ( P = 0.02), and A2 time ( P = 0.03). The mean changes in DA ratio, HC radius, InvRadMax, and Ambrosio relational thickness were significantly higher in the SMILE group in comparison with those of the PRK group (all, P < 0.05). In both groups, change in CCT was significantly correlated with changes in DA ratio and InvRadMax ( P < 0.05). CONCLUSIONSS Both SMILE and PRK refractive surgeries significantly altered corneal biomechanical properties but the changes were more prominent after SMILE.
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Affiliation(s)
- Siamak Zarei-Ghanavati
- Ophthalmology Department, Eye Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Soheyla Jafarpour
- Ophthalmology Department, Eye Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Samira Hassanzadeh
- Department of Optometry, Refractive Error Research Center, Paramedical College, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Elham Bakhtiari
- Department of ophthalmology, Eye Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Ghazaleh Daraee
- Student Research Committee, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran; and
| | - Sahar Darabi Monadi
- Student Research Committee, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran; and
| | - Mohammed Ziaei
- Faculty of Medical and Health Sciences, Department of Ophthalmology, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
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Wilson A, Jones J, Marshall J. Biomechanical Evaluation of Decellularized and Crosslinked Corneal Implants Manufactured From Porcine Corneas as a Treatment Option for Advanced Keratoconus. Front Bioeng Biotechnol 2022; 10:862969. [PMID: 35497356 PMCID: PMC9046912 DOI: 10.3389/fbioe.2022.862969] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 03/14/2022] [Indexed: 01/13/2023] Open
Abstract
Currently corneal transplantation is the main treatment for late-stage keratoconus; however, transplantation procedures are accompanied by significant risk of post-surgical complications; this in addition to supply limitations imposed by a worldwide shortage of human donor corneas, has driven the development of alternative therapies. One such therapy is the use of corneal implants derived from porcine corneas (Xenia®, Gebauer Medizintechnik GmbH, Neuhausen, DE). In contrast to human donor tissue, these implants can be produced on demand and due to the processes used pose no risks for host-immune rejection. Their use has already been demonstrated clinically in patients for preventing the progression of topographic changes in keratoconus whilst improving visual acuity. The implants are derived from natural tissue and not standardised synthetic material, whilst this likely reduces the risk of issues with bio-incompatibility, there is inevitably variability in their intrinsic mechanical properties which requires investigation. Here, speckle interferometry is employed to examine the biomechanical properties, in response to physiologically representative forces, of native porcine corneal tissue prior to processing and after a proprietary 4-stage process involving decellularization, washing, compression and crosslinking. The control lenticules had an average Young’s modulus (E) of 11.11 MPa (range 8.39–13.41 MPa), following processing average E of the lenticules increased by 127% over that of the unprocessed tissue to 25.23 MPa (range 18.32–32.9 MPa). The variability in E of the lenticules increased significantly after processing suggesting variability in the propensity of the native tissue to processing. In summary, it is possible to produce thin (<90 µm) lenticules from porcine corneas with enhanced stiffness that are effective for treating late-stage keratoconus. Due to the observed variability in the responses of lenticules to processing, interferometry could be a useful technique for ensuring quality control in commercial production via biomechanical screening.
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Affiliation(s)
- Abby Wilson
- UCL Mechanical Engineering, London, United Kingdom
- Institute of Ophthalmology, UCL, London, United Kingdom
- *Correspondence: Abby Wilson,
| | - John Jones
- Laser Optical Engineering Ltd., Donington, United Kingdom
| | - John Marshall
- Institute of Ophthalmology, UCL, London, United Kingdom
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Iglesias M, Kudsieh B, Laiseca A, Santos C, Nadal J, Barraquer R, Casaroli-Marano RP. Intraocular pressure after myopic laser refractive surgery measured with a new Goldmann convex prism: correlations with GAT and ORA. BMC Ophthalmol 2022; 22:79. [PMID: 35168601 PMCID: PMC8849021 DOI: 10.1186/s12886-022-02309-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 02/09/2022] [Indexed: 12/04/2022] Open
Abstract
Background The purpose of this study is to describe measurements using a newly developed modified Goldmann convex tonometer (CT) 1 year after myopic laser refractive surgery. Intraocular pressure (IOP) measurements were compared with IOP values obtained by Goldmann applanation tonometer (GAT), and Ocular Response Analyzer (ORA). Methods Prospective double-masked study performed on thirty eyes of thirty patients that underwent laser in situ keratomileusis (LASIK; n = 19) or photorefractive keratectomy (PRK; n = 11). IOP was measured before and 3 and 12 months after surgery. Intraclass correlation coefficient (ICC) and Bland-Altman plot were calculated to assess the agreement between GAT, CT, IOPg (Goldmann-correlated IOP) and IOPcc (corneal-compensated IOP) from ORA. Results Twelve months after LASIK, IOP measured with CT showed the best correlation with IOP measured with GAT before surgery (GATpre) (ICC = 0.886, 95% CI: 0.703–0.956) (15.60 ± 3.27 vs 15.80 ± 3.22; p < 0.000). However, a moderate correlation was found for IOP measured with IOPcc and CT 12 months after LASIK (ICC = 0.568, 95% CI: − 0.185 – 0.843) (15.80 ± 3.22 vs 12.87 ± 2.77; p < 0.004). Twelve months after PRK, CT showed a weak correlation (ICC = − 0.266, 95% CI: − 3.896 – 0.663), compared to GATpre (17.30 ± 3.47 vs 16.01 ± 1.45; p < 0.642), as well as poor correlation (ICC = 0.256, 95% CI: − 0.332 – 0.719) with IOPcc (17.30 ± 3.47 vs 13.38 ± 1.65; p < 0.182). Conclusions Twelve months after LASIK, IOP measured with CT strongly correlated with GAT before surgery and could therefore provide an alternative method for measuring IOP after this surgery. More studies regarding this new convex prism are needed to assess its accuracy.
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Affiliation(s)
- María Iglesias
- Instituto Universitario Barraquer, Barraquer Ophthalmology Centre, Laforja 88, 08012, Barcelona, Spain.
| | - Bachar Kudsieh
- Department of Ophthalmology, Hospital Universitario Puerta De Hierro, 28222, Madrid, Spain
| | - Andrea Laiseca
- Instituto Universitario Barraquer, Barraquer Ophthalmology Centre, Laforja 88, 08012, Barcelona, Spain
| | - Cristina Santos
- Unitat Antropologia Biològica, Department Biologia Animal, Biologia Vegetal i Ecologia, Universitat Autònoma de Barcelona (UAB), 08193, Barcelona, Spain
| | - Jeroni Nadal
- Instituto Universitario Barraquer, Barraquer Ophthalmology Centre, Laforja 88, 08012, Barcelona, Spain
| | - Rafael Barraquer
- Instituto Universitario Barraquer, Barraquer Ophthalmology Centre, Laforja 88, 08012, Barcelona, Spain.,International University of Catalunya (UIC), 08017, Barcelona, Spain
| | - Ricardo P Casaroli-Marano
- Department of Surgery, School of Medicine and Hospital Clinic de Barcelona, University of Barcelona (UB), 08036, Barcelona, Spain
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Duch F, López-Marín I, Alonso-Aliste F, Hernández-Barahona-Campos M, Manito SC, Sánchez-Trancón Á, Cadarso L, Sánchez-González JM, Fernández J. Influence of tomographic and biomechanical corneal indexes on myopic refractive surgery indications: A multicenter study. Eur J Ophthalmol 2021; 32:2630-2637. [PMID: 34751040 DOI: 10.1177/11206721211054725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
PURPOSE To evaluate the influence of corneal tomographic and biomechanical indexes on the refractive technique indication. METHODS A total of 251 eyes from 251 patients interested in refractive surgery were enrolled in this cross-sectional and multicenter study. Previous to the surgeon decision, a preoperative protocol was performed by refractive optometrists, containing four sections: refraction, biometry, corneal tomography and biomechanics. The refractive surgeons made a first decision based only on refraction, biometric and tomographic information. Biomechanical indexes were revealed, and refractive surgeons made a second indication. Additionally, for Laser-Assisted in-situ Keratomileusis cases, the percent tissue altered were calculated. Possible indications were no refractive surgery, photorefractive keratectomy, Laser-Assisted in-situ Keratomileusis or intraocular Collamer lens. RESULTS After the first surgery indication, the distribution was photorefractive keratectomy (47.4%), Laser-Assisted in-situ Keratomileusis (48.2%) while intraocular Collamer lens achieved 2.8%. This proportion changed significantly after the second indication regarding corneal biomechanics and photorefractive keratectomy and Laser-Assisted in-situ Keratomileusis decreased by 24% while intraocular Collamer lens increased 19%. A total of 69 eyes changed the indication (27.5%) and 182 eyes (72.5%) remained unchanged. All indications changes were from photorefractive keratectomy or Laser-Assisted in-situ Keratomileusis to intraocular Collamer lens or no surgery. Indication changes to intraocular Collamer lens were observed in 49 eyes (71%). Tomographic, biomechanical indexes, ablation depth and percent tissue altered achieved statistically significant differences between eyes without and with indication changes (all, P < .01). CONCLUSION New corneal biomechanical indexes could change the indication decision regarding biometric and tomographic data alone. Intraocular Collamer len was the preferred indication for eyes at risk of ectasia or with subclinical keratoconus due to corneal biomechanical parameters.
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Affiliation(s)
- Francesc Duch
- Refractive Surgery Department, 537040Institut Català de Retina, Spain
| | | | | | | | | | | | - Luís Cadarso
- Refractive Surgery Department, Cadarso Clinic, Spain
| | - José-María Sánchez-González
- Refractive Surgery Department, Tecnolaser Clinic Vision, Spain.,Physics of Condensed Matter Department, Optics Area, 16778University of Seville, Spain
| | - Joaquín Fernández
- Refractive Surgery Department, Qvision, 221663Vithas Virgen del Mar Hospital, Spain
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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] [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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Janknecht P. Is it Possible to Derive the Dresdner Correction Formula Using a Finite Element Program? Klin Monbl Augenheilkd 2021; 239:1262-1272. [PMID: 34243213 DOI: 10.1055/a-1478-3833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
INTRODUCTION The aim was to construct a model cornea by CAD and finite element software to find out how the intraocular pressure compares to the forces for applanation at the outside of the model cornea. These data were to be compared to the Dresdner correction formula. Thereby, it was possible to find out whether the model was plausible and to find hints as to why a correction for how the intraocular pressure depends on the corneal thickness is necessary at all. METHODS Using the open-source software FreeCad and geometrical data for the cornea of the literature, an average cornea was constructed. On this average cornea, a finite element analysis was performed using the free software z88aurora. The intraocular pressure was measured by applanation of the outer cornea. The necessary forces were analysed. RESULTS In this model, the intraocular pressure had to be corrected depending on the corneal thickness. The correction factor was kmean; finite elements = 19.17 - 0.0334*corneal thickness. The necessary correction did not exclusively depend on the relation between the endothelial area and the area of the outer cornea: for this relation alone the correction would have been karea-relation = 1.0361 - 0.0006*corneal thickness. DISCUSSION The model correction formula was close to the Dresdner formula. The relation between endothelial area and the area of the outer cornea could only explain about half of the necessary correction.
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Effective elastic modulus of an intact cornea related to indentation behavior: A comparison between the Hertz model and Johnson-Kendall-Roberts model. Exp Eye Res 2021; 209:108670. [PMID: 34129848 DOI: 10.1016/j.exer.2021.108670] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 05/24/2021] [Accepted: 06/10/2021] [Indexed: 11/24/2022]
Abstract
In this study, a macro-indentation test on the submillimeter scale was performed to analyze the indentation behavior of an intact cornea under physiological pressures. The Hertz and Johnson-Kendall-Roberts (JKR) models were employed to solve the elastic modulus (E) of the intact cornea. The relevant detailed analysis showed that the JKR model, which accounted for the contribution from the adhesion energy, could be used to obtain the E values that were more than two-folds of those obtained from the Hertz model, which only considered the external force. Compared with the uniaxial tension test in vitro, unlike the elastic Hertz-model, the E values under physiological pressures that were obtained with the JKR model were between the lower and upper limits of corneal material. This phenomenon indicated that the JKR model could be used to obtain reasonably effective E values of an intact cornea under physiological pressures.
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Lanza M, De Rosa L, Sbordone S, Boccia R, Gironi Carnevale UA, Simonelli F. Analysis of Corneal Distortion after Myopic PRK. J Clin Med 2020; 10:jcm10010082. [PMID: 33379378 PMCID: PMC7794860 DOI: 10.3390/jcm10010082] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 12/14/2020] [Accepted: 12/24/2020] [Indexed: 01/22/2023] Open
Abstract
The purpose of the study is to evaluate the corneal biomechanical properties (CBP) and their behaviors after myopic refractive surgery both with Ocular Response Analyzer (ORA) and Corvis ST (CST). This retrospective study included 145 eyes of 145 patients with a mean age of 33.13 ± 9.24 years, who underwent myopic photorefractive keratectomy (PRK) for a refractive defect, measured as spherical equivalent, of mean −4.69 ± 2.04 D and have been evaluated before surgery and at 1, 3 and 6 months follow-up. Corneal hysteresis (CH) and corneal resistance factor (CRF) values significantly decreased after 1 month and remained statistically stable during further follow-ups. CST parameters had a different evolution: only second applanation time (AT2) differences showed a significant variation after 1 month that did not statistically change over time. Highest concavity deformation amplitude (HCDA), highest concavity peak distance (HCPD), first applanation time (AT1) and velocity (AV1) showed continuous significant differences both after 3 and after 6 months. This study suggests that after central surface ablation surgery, such as myopic PRK, corneal shape is remodeling, and its deformation parameters are going to change even at 6 months follow-up. This indicates that it should be important to evaluate refractive surgery patients during a longer follow-up because this could allow earlier diagnosis and better management of late-onset complications.
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Sachdev GS, Ramamurthy S. Decade - long journey with small incision lenticule extraction: The learnings. Indian J Ophthalmol 2020; 68:2705-2710. [PMID: 33229646 PMCID: PMC7856951 DOI: 10.4103/ijo.ijo_2622_20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Over the past decade, small incision lenticule extraction (SMILE) has revolutionized the field of keratorefractive surgery. With the promise of superior corneal biomechanics and reduced postoperative dry eye, SMILE afforded a distinct advantage over flap-based procedures. Our evolving understanding of the surgical technique and management of its unique complications has further enhanced the outcomes. This review will highlight specific pearls on various preoperative and intraoperative principles allowing optimization of outcomes with SMILE.
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Affiliation(s)
- Gitansha S Sachdev
- Refractive Services, The Eye Foundation, RS Puram, Coimbatore, Tamil Nadu, India
| | - Shreyas Ramamurthy
- Refractive Services, The Eye Foundation, RS Puram, Coimbatore, Tamil Nadu, India
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Iglesias M, Yebra F, Kudsieh B, Laiseca A, Santos C, Nadal J, Barraquer R, Casaroli-Marano RP. New applanation tonometer for myopic patients after laser refractive surgery. Sci Rep 2020; 10:7053. [PMID: 32341434 PMCID: PMC7184562 DOI: 10.1038/s41598-020-64013-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 04/07/2020] [Indexed: 11/25/2022] Open
Abstract
This study assesses the agreement between intraocular pressure (IOP) measurements taken with the Goldmann applanation tonometer (GAT) and a new experimental applanation tonometer with a convexly shaped apex (CT) after laser myopic refractive surgery. Two different CT radii (CT1 and CT2) were designed with a finite element analyser, and a prospective double masked study on 102 eyes from 102 patients was carried out. A Bland-Altman plot and intra-class correlation coefficient (ICC) were calculated to assess the agreement between GAT measurements and the measurements of both CT1 and CT2 before and after myopic laser assisted in situ keratomileusis (LASIK; n = 73) and photorefractive keratectomy (PRK; n = 29). We evaluated a subset of two subgroups (n = 36 each) for intra and inter-observer (IA/IE) error. From the whole cohort, the best IOP agreement was observed between GATpre and CT1post surgery: 16.09 ± 2.92 vs 16.42 ± 2.87 (p < 0.001); ICC = 0.675 (95% CI: 0.554-0.768). In the analysis of LASIK vs PRK, GATpre and CT1post showed the highest agreement, although LASIK measurements were more accurate than PRK, as the ICC = 0.718 (95% CI: 0.594-0.812) and ICC = 0.578 (95% CI: 0.182-0.795) respectively. Excellent agreement was observed for IA/IE, and there was an ICC > 0.8 (95% CI) in all cases. CT1 proved more accurate in the LASIK subgroup. In conclusion, our new version of GAT could be used with post-surgery LASIK patients as a more accurate measurement device compared to the current reference tonometer.
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Affiliation(s)
- María Iglesias
- Instituto Universitario Barraquer, Barraquer Ophthalmology Centre, Barcelona, 08012, Spain.
| | - Francisco Yebra
- Department of Physics, University of Vigo, 36310, Galicia, Spain
| | - Bachar Kudsieh
- Department of Ophthalmology, Hospital Universitario Puerta De Hierro, 28222, Madrid, Spain
| | - Andrea Laiseca
- Instituto Universitario Barraquer, Barraquer Ophthalmology Centre, Barcelona, 08012, Spain
| | - Cristina Santos
- Unitat Antropologia Biològica, Department Biologia Animal, Biologia Vegetal i Ecologia, Universitat Autònoma de Barcelona (UAB), Barcelona, 08193, Spain
| | - Jeroni Nadal
- Instituto Universitario Barraquer, Barraquer Ophthalmology Centre, Barcelona, 08012, Spain
| | - Rafael Barraquer
- Instituto Universitario Barraquer, Barraquer Ophthalmology Centre, Barcelona, 08012, Spain
- International University of Catalunya (UIC), Barcelona, 08017, Spain
| | - Ricardo P Casaroli-Marano
- Department of Surgery, School of Medicine and Hospital Clinic de Barcelona, University of Barcelona (UB), Barcelona, 08036, Spain
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Voronin GV, Bubnova IA. [Changes in biomechanical properties of the cornea after keratorefractive surgery]. Vestn Oftalmol 2019; 135:108-112. [PMID: 31573565 DOI: 10.17116/oftalma2019135041108] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Biomechanical properties of the cornea are important for the functioning of the ocular optical system. They affect such qualities of the system as correct diffraction and resistance to different external action. Keratorefractive surgery widely used in clinical practice nowadays significantly upsets corneal biomechanics, which introduces a margin of error for IOP measurements done by different methods. The article reviews literature devoted to the problem of changes of corneal biomechanical properties after refractive surgeries.
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Affiliation(s)
- G V Voronin
- Research Institute of Eye Diseases, 11A Rossolimo St., Moscow, Russian Federation, 119021; I.M. Sechenov First Moscow State Medical University, Department of Ophthalmology, 8-2 Trubetskaya St., Moscow, Russian Federation, 119991
| | - I A Bubnova
- Research Institute of Eye Diseases, 11A Rossolimo St., Moscow, Russian Federation, 119021
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