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Evaluation of morphological features: femtosecond-LASIK flap vs. SMILE cap, and the effects on corneal higher-order aberrations. Graefes Arch Clin Exp Ophthalmol 2022; 260:3993-4003. [PMID: 36166075 DOI: 10.1007/s00417-022-05841-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 08/14/2022] [Accepted: 09/20/2022] [Indexed: 11/04/2022] Open
Abstract
PURPOSE The aim of this study is to evaluate morphological features of corneal flap/cap and the correlations with corneal higher-order aberrations (HOAs) changes after femtosecond laser in situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE). METHODS This was a retrospective study. Pre- and postoperative (1 and 3 months) corneal HOAs were assessed with Pentacam HR. The corneal flap/cap thickness at 32 points (± 1.5 mm, ± 2 mm, ± 2.5 mm, and ± 3 mm from the corneal vertex on meridian 0°/45°/90°/135°) were measured using anterior segment optical coherence tomography at 3 months postoperatively. Morphological features of corneal flap/cap including predictability (P), uniformity (U), and symmetry (S) were calculated and used for correlation analysis with corneal HOAs changes. RESULTS Eighty-six eyes (44 patients) and ninety-six eyes (50 patients) were involved in FS-LASIK and SMILE groups, respectively. Significant thicker corneal flap/cap than the predicted was observed at each measuring point and meridian in both groups (difference > 2.225 μm, the within-subject standard deviation over 6-mm optical zone). There was no statistically significant difference in predictability of corneal flap/cap thickness, while U6 mm (P < .0001), U0 (P < .001), U45 (P = .002), U90 (P < .0001), U135 (P = .004), S6 mm (P < .0001), S0 (P < .001), and S90 (P < .0001) over 6 mm zone were less in SMILE than in FS-LASIK. The changes of corneal tHOAs, Z (3, - 1), Z (3, 1), and SA were significantly correlated with morphological features of corneal flap/cap. CONCLUSION Both FS-LASIK and SMILE had good predictability in flap or cap thickness, while the uniformity and symmetry of SMILE cap were better than FS-LASIK flap. The quality of flap/cap was closely associated with the changes of corneal HOAs.
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Miraftab M, Hashemi H, Aghamirsalim M, Fayyaz S, Asgari S. Matched comparison of corneal higher order aberrations induced by SMILE to femtosecond assisted LASIK and to PRK in correcting moderate and high myopia: 3.00mm vs. 6.00mm. BMC Ophthalmol 2021; 21:216. [PMID: 33992084 PMCID: PMC8122548 DOI: 10.1186/s12886-021-01987-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 05/10/2021] [Indexed: 11/25/2022] Open
Abstract
Background The refractive surgeries induce corneal higher order aberrations (C-HOAs). In this study, change of C-HOAs after small-incision lenticule extraction (SMILE) compared to femtosecond assisted laser in situ keratomileusis (femto-LASIK), and to photorefractive keratectomy with mitomycin-C (PRK) under photopic and mesopic conditions. Methods In this prospective study, age, gender, and apical corneal thickness (ACT) matched cases with moderate myopia [spherical equivalent (SE) 3.00 to 6.00D) to high myopia (SE > 6.00D)] were enrolled. In addition to visual acuity and refraction, total C-HOA, coma, spherical aberration (SA), and trefoil in the 3- and 6-mm zones were measured before and 3 and 6 months after surgery. Results Overall, 372 moderate myopia cases (124 eyes of 124 individuals in each surgical group) and 171 high myopia cases (57 eyes of 57 individuals in each surgical group) were enrolled. At baseline, the differences in age, gender, ACT, uncorrected and corrected visual acuity, and SE were not statistically significant between subgroups of surgical methods within each myopia group (all P > 0.05). At 12 months, in the moderate myopia group, there was less increase in 6-mm zone total C-HOA, coma, and SA with SMILE compared to the other groups (all P < 0.05). In the high myopia group, there was greater increase in photopic total C-HOA and trefoil and less increase in mesopic SA with SMILE (all P < 0.05). Conclusions In correction of moderate myopia, SMILE has better results in mesopic condition. In high myopia correction, femto-LASIK and PRK have better results in photopic and SMILE in mesopic condition.
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Affiliation(s)
- Mohammad Miraftab
- Noor Ophthalmology Research Center, Noor Eye Hospital, No. 96 Esfandiar Blvd., Vali'asr Ave, Tehran, Iran
| | - Hassan Hashemi
- Noor Ophthalmology Research Center, Noor Eye Hospital, No. 96 Esfandiar Blvd., Vali'asr Ave, Tehran, Iran.
| | | | - Shiva Fayyaz
- Noor Ophthalmology Research Center, Noor Eye Hospital, No. 96 Esfandiar Blvd., Vali'asr Ave, Tehran, Iran
| | - Soheila Asgari
- Noor Ophthalmology Research Center, Noor Eye Hospital, No. 96 Esfandiar Blvd., Vali'asr Ave, Tehran, Iran
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Comparison of visual quality after Femto-LASIK and TransPRK in patients with low and moderate myopia. Int Ophthalmol 2020; 40:1419-1428. [DOI: 10.1007/s10792-020-01308-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 02/08/2020] [Indexed: 11/25/2022]
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Chen X, Wang Y, Zhang J, Yang SN, Li X, Zhang L. Comparison of ocular higher-order aberrations after SMILE and Wavefront-guided Femtosecond LASIK for myopia. BMC Ophthalmol 2017; 17:42. [PMID: 28388896 PMCID: PMC5384151 DOI: 10.1186/s12886-017-0431-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 03/31/2017] [Indexed: 11/17/2022] Open
Abstract
Background To compare changes in higher-order aberrations (HOAs) following small incision lenticule extraction (SMILE) and wavefront-guided femtosecond laser-assisted in situ keratomileusis (WFG FS-LASIK), and to investigate correlations between preoperative spherical equivalence (SE) and components of HOAs affecting visual quality. Methods Sixty-five myopic eyes from 38 patients were enrolled in the study retrospectively, either having undergone SMILE or WFG FS-LASIK. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive error, and individual Zernike coefficients of 3rd- to 6th-order HOAs were measured before and 3 months after the surgeries and were compared using the Mann-Whitney test or Student’s t-test. Additional generalized estimating equation analyses (GEE) were used to control for within-subject biases in individual Zernike coefficients between the right and left eyes of the same patients. Results There was no significant difference in UDVA or CDVA after WFG FS-LASIK (Mean ± SD: −0.02 ± 0.07 and −0.04 ± 0.22 respectively, in logMAR) and after SMILE (−0.01 ± 0.06 and −0.04 ± 0.04 respectively). However, greater vertical coma aberration was found after SMILE (p = 0.036). Preoperative SE was correlated to induced horizontal coma (r = −0.608, p = 0.001) in WFG FS-LASIK, and correlated to induced vertical coma (r = −0.459, p = 0.003) in SMILE. Conclusions Both SMILE and WFG FS-LASIK can achieve planned visual outcomes in correcting myopia and myopic astigmatism. However, higher vertical coma was shown in SMILE than WFG FS-LASIK which might be a potentially impact factor for patients’ vision under certain lighting conditions and needs further investigation.
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Affiliation(s)
- Xiaoqin Chen
- Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, No 4. Gansu Rd, Heping District, Tianjin, 300020, China
| | - Yan Wang
- Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, No 4. Gansu Rd, Heping District, Tianjin, 300020, China.
| | - Jiamei Zhang
- Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, No 4. Gansu Rd, Heping District, Tianjin, 300020, China
| | - Shun-Nan Yang
- Vision Performance Institute, Pacific University College of Optometry, Forest Grove, OR, USA
| | - Xiaojing Li
- First Hospital of Qinhuangdao, Qinhuangdao, Hebei, China
| | - Lin Zhang
- Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, No 4. Gansu Rd, Heping District, Tianjin, 300020, China
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Kulikova IL, Shlenskaya OV, Chapurin NV. [Analysis of corneal biomechanical changes after femtosecond laser-assisted laser in situ keratomileusis in children with hyperopic anisometropia]. Vestn Oftalmol 2017; 133:30-36. [PMID: 28745654 DOI: 10.17116/oftalma2017133330-36] [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] [Indexed: 06/07/2023]
Abstract
AIM to analyze corneal hysteresis (CH) and corneal resistance factor (RF) readings obtained with the Reichert Ocular Response Analyzer (ORA) before and after hyperopic femtolaser-assisted laser in situ keratomileusis (FS-LASIK) in children with anisometropia as well as to establish factors that may cause changes in these parameters. MATERIAL AND METHODS CH and RF were evaluated before and 1.5 years after FS-LASIK performed on amblyopic eyes of 28 patients aged 6-14 years. Preoperatively, there was a correlation between CH and RF (r=0.41, p=0.03). No correlation was found between CH and age (r=-0.02, p=0.82) or between CH (r=0.00, p=0.98), RF (r=0.04, p=0.83), and cornea thickness. RESULTS The mean preoperative CH was 12.56±1.21 mmHg, RF 12.31±1.57 mmHg. Postoperatively, a statistically significant change occurred to both CH (by 0.97±1.51 mmHg, p=0.002) and RF (by 1.42±1.55 mmHg, p=0.000). No correlation was found between CH before and after surgery (r=0.11, p=0.57) as well as between the ablation depth and changes in CH (r=0,04, p=0.83) and RF (r=0.21, p=0.28). Regression analysis showed that the extent of CH (r2=0.52, p=0.00) and RF (r2=0,48, p=0.00) changes was closely related to their preoperative values. CONCLUSION The statistically significant relative change in CH and RF after hyperopic FS-LASIK was 8% and 12%, respectively. CH and RF changes correlated with their preoperative values, but not with the ablation depth or cornea thickness.
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Affiliation(s)
- I L Kulikova
- Cheboksary branch of S. Fyodorov Eye Microsurgery Federal State Institution, 10 Traktorostroiteley St., Cheboksary, Chuvash Republic, Russia, 428000
| | - O V Shlenskaya
- Cheboksary branch of S. Fyodorov Eye Microsurgery Federal State Institution, 10 Traktorostroiteley St., Cheboksary, Chuvash Republic, Russia, 428000
| | - N V Chapurin
- Cheboksary branch of S. Fyodorov Eye Microsurgery Federal State Institution, 10 Traktorostroiteley St., Cheboksary, Chuvash Republic, Russia, 428000
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Abstract
PURPOSE OF REVIEW This article summarizes the state-of-the-art in clinical corneal biomechanics, including procedures in which biomechanics play a role, and the clinical consequences in terms of error in estimating intraocular pressure (IOP). RECENT FINDINGS Corneal biomechanical response to refractive surgery can be categorized into either stable alteration of surface shape and thus visual outcome, or unstable biomechanical decompensation. The stable response is characterized by central flattening and peripheral steepening that is potentiated in a stiffer cornea. Two clinical devices for assessing corneal biomechanics do not yet measure classic biomechanical properties, but rather provide assessment of corneal deformation response. Biomechanical parameters are a function of IOP, and both the cornea and sclera become stiffer as IOP increases. Any assessment of biomechanical parameters must include IOP, and one value of stiffness does not adequately characterize a cornea. SUMMARY Corneal biomechanics plays a role in the outcomes of any procedure in which lamellae are transected. Once the corneal structure has been altered in a manner that includes central thinning, IOP measurements with applanation tonometry are likely not valid, and other technologies should be used.
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Zhang C, Ding H, He M, Liu L, Liu L, Li G, Niu B, Zhong X. Comparison of Early Changes in Ocular Surface and Inflammatory Mediators between Femtosecond Lenticule Extraction and Small-Incision Lenticule Extraction. PLoS One 2016; 11:e0149503. [PMID: 26937680 PMCID: PMC4777367 DOI: 10.1371/journal.pone.0149503] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 01/28/2016] [Indexed: 11/18/2022] Open
Abstract
Purpose To evaluate the short-term changes in ocular surface measures and tear inflammatory mediators after femtosecond lenticule extraction (FLEx) and small-incision lenticule extraction (SMILE) procedures. Methods Eighteen subjects (18 eyes) underwent FLEx and 23 subjects (23 eyes) underwent SMILE in this single-center and prospective study. Central corneal sensitivity, Schirmer I test (SIT), noninvasive tear breakup time (NI-TBUT), tear meniscus height, corneal fluorescein (FL) staining, and ocular surface disease index (OSDI) were assessed in all patients. Concentrations of interleukin-1α (IL-1α), tumor necrosis factor-α (TNF-α), nerve growth factor (NGF), interferon-γ (IFN-γ), transforming growth factor-β1 (TGF-β1) and matrix metalloproteinase-9 (MMP-9) in collected tears were measured by multiplex antibody microarray. Results Central corneal sensitivity was reduced in both groups, but the scores in the SMILE group were higher than those in the FLEx group at all time points postoperatively (P<0.01). Lower FL scores and longer NI-BUT were observed in the SMILE group 1 week after surgery (P<0.05). OSDI scores in both groups increased rapidly at 1 day and 1 week postoperatively, then returned to their preoperative levels within 1 month (P<0.05). There were no significant differences in SIT or tear meniscus height between the two groups. Lower and faster recovery of tear NGF, TGF-β1 and IL-1α concentration were found in the SMILE group compared to the FLEx group postoperatively. No significant difference was found in tear TNF-α, IFN-γ and MMP-9 for either group before or after surgery. Tear NGF, TGF-β1 and IL-1α show a correlation with ocular surface changes after FLEx or SMILE surgery. Conclusion SMILE has superiority over FLEx in early ocular surface changes and NGF, TGF-β1 and IL-1α may contribute to the process of ocular surface recovery. Trial Registration ClinicalTrials.gov NCT02540785
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Affiliation(s)
- Chi Zhang
- Zhongshan Ophthalmic Center and State Key Laboratory of Ophthalmology, Sun Yat-sen University, Guangzhou 510060, China
- Department of Ophthalmology, The First People’s Hospital of Foshan, Foshan 528000, China
| | - Hui Ding
- Hainan Eye Hospital, Zhongshan Ophthalmic Center, Sun Yat-sen University, Haikou 570311, China
| | - Miao He
- Zhongshan Ophthalmic Center and State Key Laboratory of Ophthalmology, Sun Yat-sen University, Guangzhou 510060, China
| | - Lina Liu
- Hainan Eye Hospital, Zhongshan Ophthalmic Center, Sun Yat-sen University, Haikou 570311, China
| | - Liangping Liu
- Zhongshan Ophthalmic Center and State Key Laboratory of Ophthalmology, Sun Yat-sen University, Guangzhou 510060, China
| | - Gang Li
- Hainan Eye Hospital, Zhongshan Ophthalmic Center, Sun Yat-sen University, Haikou 570311, China
| | - Bing Niu
- Shanghai Key Laboratory of Bio-energy Crops, School of Life Science, Shanghai University, Shanghai 200444, China
- Schepens Eye Research Institute, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, United States of America
| | - Xingwu Zhong
- Zhongshan Ophthalmic Center and State Key Laboratory of Ophthalmology, Sun Yat-sen University, Guangzhou 510060, China
- Hainan Eye Hospital, Zhongshan Ophthalmic Center, Sun Yat-sen University, Haikou 570311, China
- * E-mail:
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Small-incision lenticule extraction (SMILE): outcomes of 722 eyes treated for myopia and myopic astigmatism. Graefes Arch Clin Exp Ophthalmol 2015; 254:399-405. [DOI: 10.1007/s00417-015-3226-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 11/09/2015] [Accepted: 11/12/2015] [Indexed: 10/22/2022] Open
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Sinha Roy A, Dupps WJ, Roberts CJ. Comparison of biomechanical effects of small-incision lenticule extraction and laser in situ keratomileusis: finite-element analysis. J Cataract Refract Surg 2014; 40:971-80. [PMID: 24857440 DOI: 10.1016/j.jcrs.2013.08.065] [Citation(s) in RCA: 137] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 07/12/2013] [Accepted: 08/14/2013] [Indexed: 11/18/2022]
Abstract
PURPOSE To theoretically compare the corneal stress distribution of laser in situ keratomileusis (LASIK) with the stress distribution of small-incision lenticule extraction. SETTING Cleveland Clinic Cole Institute, Cleveland, and The Ohio State University, Columbus, Ohio, USA. DESIGN Computational modeling study. METHODS A finite-element anisotropic collagen fiber-dependent model of myopic surgery using patient-specific corneal geometry was constructed for LASIK, small-incision lenticule extraction, and a geometry analog model with unaltered material properties from preoperative but with postoperative geometry including thickness. Surgical parameters, magnitude of myopic correction, LASIK flap thickness, and lenticule depth in small-incision lenticule extraction were varied. Two sets of models, 1 with uniform and 1 with depth-dependent material properties, were constructed. RESULTS Stress distribution between small-incision lenticule extraction simulations and the geometry analog model were similar. In contrast, LASIK consistently reduced stress in the flap and increased stress in the residual stromal bed (RSB) compared with the geometry analog model. An increase in flap thickness or lenticule depth resulted in a greater increase in RSB stress in the LASIK model than in the small-incision lenticule extraction model. CONCLUSIONS Small-incision lenticule extraction may present less biomechanical risk to the residual bed of susceptible corneas than comparable corrections involving LASIK flaps. Deeper corrections in the stroma may be possible in small-incision lenticule extraction without added risk for ectasia. FINANCIAL DISCLOSURES Proprietary or commercial disclosures are listed after the references.
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Affiliation(s)
- Abhijit Sinha Roy
- From the Cole Eye Institute (Sinha Roy, Dupps), Cleveland Clinic Foundation, the Department of Biomedical Engineering (Dupps), Lerner Research Institute, and the Department of Biomedical Engineering (Dupps), Case Western Reserve University, Cleveland, and the Departments of Ophthalmology and Biomedical Engineering (Roberts), The Ohio State University, Columbus, Ohio, USA
| | - William J Dupps
- From the Cole Eye Institute (Sinha Roy, Dupps), Cleveland Clinic Foundation, the Department of Biomedical Engineering (Dupps), Lerner Research Institute, and the Department of Biomedical Engineering (Dupps), Case Western Reserve University, Cleveland, and the Departments of Ophthalmology and Biomedical Engineering (Roberts), The Ohio State University, Columbus, Ohio, USA
| | - Cynthia J Roberts
- From the Cole Eye Institute (Sinha Roy, Dupps), Cleveland Clinic Foundation, the Department of Biomedical Engineering (Dupps), Lerner Research Institute, and the Department of Biomedical Engineering (Dupps), Case Western Reserve University, Cleveland, and the Departments of Ophthalmology and Biomedical Engineering (Roberts), The Ohio State University, Columbus, Ohio, USA.
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The association between femtosecond laser flap parameters and ocular aberrations after uncomplicated custom myopic LASIK. Graefes Arch Clin Exp Ophthalmol 2013; 251:2155-62. [DOI: 10.1007/s00417-013-2328-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Revised: 03/06/2013] [Accepted: 03/13/2013] [Indexed: 10/27/2022] Open
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Comparison of corneal sensitivity between FS-LASIK and femtosecond lenticule extraction (ReLEx flex) or small-incision lenticule extraction (ReLEx smile) for myopic eyes. Graefes Arch Clin Exp Ophthalmol 2013; 251:1645-54. [DOI: 10.1007/s00417-013-2272-0] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 01/14/2013] [Accepted: 01/22/2013] [Indexed: 10/27/2022] Open
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Hsieh YT, Wang IJ, Hu FR. Anterior corneal optical irregularity measured by higher-order aberrations induced by a broad beam excimer laser. Clin Exp Optom 2012; 95:522-30. [PMID: 22591225 DOI: 10.1111/j.1444-0938.2012.00718.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND The aim was to analyse anterior corneal optical irregularity in patients receiving photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with a conventional broad beam laser. METHODS Pre- and post-operative anterior corneal aberrations including Zernike coefficients and root mean squares of higher-order aberrations were measured and derived with a Placido-ring-based corneal topographer and wavefront software, respectively, from 768 right eyes of patients receiving either PRK or LASIK for myopia with a conventional broad beam excimer laser in National Taiwan University Hospital, Taipei, Taiwan. Multiple linear regression models selected by Mallows' Cp criteria were used to evaluate predictability of surgically induced aberrations and relevant factors. RESULTS Mean attempted spherical equivalent correction was -7.37 ± 2.33 D (range: -16.5 to -1.95). Root mean squares of higher-order aberrations and variances of Zernike coefficients all increased significantly after surgery (p < 0.01). All post-operative higher-order aberrations increased with the amount of attempted myopic correction and secondary astigmatism increased with attempted cylindrical correction. LASIK surgery induced less coma and third-order aberrations but more fifth- and sixth-order aberrations than PRK, although squared partial correlation coefficients were low. Larger optic and transitional zones meant fewer higher-order aberrations after surgery. Younger patients tended to have more surgically induced aberrations in the 3.0 mm pupil zone. CONCLUSIONS Anterior corneal optical irregularity increased tremendously after refractive surgery by conventional broad beam lasers and correlated with greater attempted myopic correction, younger age and a smaller treatment zone. The effect of corneal flaps on post-operative corneal irregularity differed trivially.
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Affiliation(s)
- Yi-Ting Hsieh
- Department of Ophthalmology, Buddhist Tzu Chi General Hospital, Taipei, Taiwan
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Uzbek AK, Kamburoğlu G, Mahmoud AM, Roberts CJ. Change in biomechanical parameters after flap creation using the Intralase femtosecond laser and subsequent excimer laser ablation. Curr Eye Res 2011; 36:614-9. [PMID: 21657826 DOI: 10.3109/02713683.2010.546952] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE This study aims to investigate the effect of both flap creation and laser ablation on corneal hysteresis (CH) and corneal resistance factor (CRF), as well as the inward applanation signal amplitude produced by the ocular response analyzer (ORA), immediately following each step of the LASIK procedure using the Intralase femtosecond laser for flap creation. METHODS A total of 66 eyes of 35 subjects who underwent Intra-LASIK surgery were prospectively enrolled in this study. Changes in the CH, CRF, and amplitude of the first applanation peak (Peak 1) of the infrared signal were measured preoperatively, immediately after flap elevation and repositioning, as well as subsequent to laser ablation in all eyes. Repeated measures analysis of variance (ANOVA) was performed with a post-test of contrast variable profiles to investigate changes following each step of the procedure. RESULTS The repeated measures ANOVA indicated a significant difference (p < 0.001) among the three time points for CH, CRF, and Peak 1. There was no significant change in CH (p = 0.20) or CRF (p = 0.57) after flap creation, but there was significant decrease in these parameters following laser ablation (p < 0.0001), when compared to values obtained pre-operatively. There was a significant decrease in Peak 1 both after flap creation (p < 0.0001) and after subsequent ablation (p < 0.0001), when compared to pre-operative ORA signal peak amplitudes. CONCLUSION There is a well documented change in corneal biomechanical properties following a LASIK procedure. This study reveals that this change may be predominantly due to laser ablation. However, flap creation with the Intralase laser does produce a biomechanical consequence consistent with reduction of corneal stiffness, as measured by the reduced amplitude of Peak 1. CH and CRF do not fully characterize this change.
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AlMahmoud T, Munger R, Jackson WB. Advanced corneal surface ablation efficacy in myopia: changes in higher order aberrations. Can J Ophthalmol 2011; 46:175-81. [PMID: 21708087 DOI: 10.3129/i10-104] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
OBJECTIVE To evaluate the change of ocular and corneal higher order aberrations (HOAs) after wavefront-guided advanced surface ablation (WF-ASA) for myopia using 4 different epithelial management techniques (AA-PRK, LASEK, Epi-PRK, and Epi-LASIK). DESIGN Retrospective single centre excimer database analysis. PARTICIPANTS Two hundred and forty eyes equally divided between the 4 WF-ASA techniques, matched for mean and range of required spherical correction. METHODS Ocular wavefront aberrations were measured using the wavescan aberrometer and corneal aberrations were obtained from corneal topography elevation maps and calculated by ray-tracing. All data were collected preoperatively and 3 months following treatment. The aberrations were described as Zernike polynomials, and analysis focused on total HOAs and spherical aberration (SA). RESULTS Three months postoperatively, there was a statistically significant surgically induced increase in total HOAs and SA both for ocular and corneal analysis (p < 0.001). There was no statistically significant difference in the induced ocular SA and HOAs between the groups, but the differences in induced corneal SA and HOAs were significant (p < 0.010). Ocular changes in SA were weakly correlated to preoperative SA (20.30, p < 0.001) but strongly correlated to applied spherical correction (20.68, p < 0.001). Surgically induced corneal SA was weakly correlated to preoperative corneal SA (20.34, p < 0.001) and applied spherical correction (20.46, p < 0.001). CONCLUSIONS Three months postoperatively, all procedures resulted in an increase in ocular and cornealHOAs and SA. Induced aberrations were most strongly correlated to the applied spherical power correction. Modifying the existing ablation pattern to compensate for induced HOAs might improve the outcome.
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Affiliation(s)
- Tahra AlMahmoud
- Department of Surgery, Faculty of Medicine and Health Sciences, United Arab Emirates University, Al Ain, UAE.
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McKelvie J, McArdle B, McGhee C. The Influence of Tilt, Decentration, and Pupil Size on the Higher-Order Aberration Profile of Aspheric Intraocular Lenses. Ophthalmology 2011; 118:1724-31. [DOI: 10.1016/j.ophtha.2011.02.025] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 02/13/2011] [Accepted: 02/14/2011] [Indexed: 12/18/2022] Open
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Keir NJ, Simpson T, Hutchings N, Jones L, Fonn D. Outcomes of wavefront-guided laser in situ keratomileusis for hyperopia. J Cataract Refract Surg 2011; 37:886-93. [DOI: 10.1016/j.jcrs.2010.12.039] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 11/25/2010] [Accepted: 12/01/2010] [Indexed: 10/18/2022]
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Kim SW, Yang H, Yoon G, Lee YJ, Kweon MN, Kim JK, Seo KY. Higher-order aberration changes after Implantable Collamer Lens implantation for myopia. Am J Ophthalmol 2011; 151:653-662.e1. [PMID: 21310383 DOI: 10.1016/j.ajo.2010.10.031] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 10/20/2010] [Accepted: 10/20/2010] [Indexed: 11/28/2022]
Abstract
PURPOSE To investigate the changes in higher-order aberrations (HOAs) induced by implantation of Implantable Collamer Lenses (STAAR Surgical) and to explain them in relation to the surgical incision and optical properties. DESIGN Prospective, observational case study. METHODS This study included 56 eyes undergoing Implantable Collamer Lens insertion for myopic correction. The corneal incision size was determined according to the amount of astigmatism. HOAs were measured before surgery and 3 months after surgery in 25 eyes having small superior incision (<3.2 mm) surgery and in 31 eyes with large superior incision (3.2 to 4.5 mm) surgery. Changes in spherical aberration, coma, trefoil, and total HOAs (third to sixth order) were analyzed. Laboratory measurements of aberration profiles of Implantable Collamer Lenses with different optical powers were performed to validate clinical measurements. RESULTS In the small-incision group, trefoil (Z(3)(-3)) and spherical aberration changed significantly (P=.004). In the large-incision group, in addition to trefoil and spherical aberration, total HOA changed significantly (mean change, 0.13 ± 0.17; P=.001). Significant correlations were observed among the incision size, the astigmatism induced, and the trefoil induced. Induced trefoil showed a predominant pattern at the orientation of the incision meridian. Optical measurement of aberrations of the Implantable Collamer Lenses confirmed the postoperative negative spherical aberration. CONCLUSIONS HOA changes after Implantable Collamer Lens insertion were increased trefoil and induced negative spherical aberration. These changes may be explained by the effect of the corneal incision and the negative spherical aberration in the Implantable Collamer Lens, respectively.
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Affiliation(s)
- Sun Woong Kim
- Department of Ophthalmology, Soonchunhyang University College of Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, Korea
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Roy AS, Dupps WJ. Patient-Specific Modeling of Corneal Refractive Surgery Outcomes and Inverse Estimation of Elastic Property Changes. J Biomech Eng 2010; 133:011002. [DOI: 10.1115/1.4002934] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The purpose of this study is to develop a 3D patient-specific finite element model (FEM) of the cornea and sclera to compare predicted and in vivo refractive outcomes and to estimate the corneal elastic property changes associated with each procedure. Both eyes of a patient who underwent laser-assisted in situ keratomileusis (LASIK) for myopic astigmatism were modeled. Pre- and postoperative Scheimpflug anterior and posterior corneal elevation maps were imported into a 3D corneo-scleral FEM with an unrestrained limbus. Preoperative corneal hyperelastic properties were chosen to account for meridional anisotropy. Inverse FEM was used to determine the undeformed corneal state that produced <0.1% error in anterior elevation between simulated and in vivo preoperative geometries. Case-specific 3D aspheric ablation profiles were simulated, and corneal topography and spherical aberration were compared at clinical intraocular pressure. The magnitude of elastic weakening of the residual corneal bed required to maximize the agreement with clinical axial power was calculated and compared with the changes in ocular response analyzer (ORA) measurements. The models produced curvature maps and spherical aberrations equivalent to in vivo measurements. For the preoperative property values used in this study, predicted elastic weakening with LASIK was as high as 55% for a radially uniform model of residual corneal weakening and 65% at the point of maximum ablation in a spatially varying model of weakening. Reductions in ORA variables were also observed. A patient-specific FEM of corneal refractive surgery is presented, which allows the estimation of surgically induced changes in corneal elastic properties. Significant elastic weakening after LASIK was required to replicate clinical topographic outcomes in this two-eye pilot study.
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Affiliation(s)
| | - William J. Dupps
- Cole Eye Institute, Department of Biomedical Engineering, and Transplant Center, Surgery Institute, Cleveland Clinic, Cleveland, OH; Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44195
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Lanchares E, Calvo B, del Buey M, Cristóbal J, Doblaré M. The Effect of Intraocular Pressure on the Outcome of Myopic Photorefractive Keratectomy: A Numerical Approach. JOURNAL OF HEALTHCARE ENGINEERING 2010. [DOI: 10.1260/2040-2295.1.3.461] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Grewal DS, Brar GS, Grewal SPS. Assessment of central corneal thickness in normal, keratoconus, and post-laser in situ keratomileusis eyes using Scheimpflug imaging, spectral domain optical coherence tomography, and ultrasound pachymetry. J Cataract Refract Surg 2010; 36:954-64. [PMID: 20494767 DOI: 10.1016/j.jcrs.2009.12.033] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Revised: 11/02/2009] [Accepted: 12/07/2009] [Indexed: 11/29/2022]
Abstract
PURPOSE To compare the central corneal thickness (CCT) in normal eyes, eyes with keratoconus, and eyes after laser in situ keratomileusis (LASIK) using 3 methods. SETTING Cornea Clinic, Grewal Eye Institute, Chandigarh, India. METHODS In this study, CCT was measured by sequential Scheimpflug imaging, spectral-domain anterior segment optical coherence tomography (AS-OCT), and ultrasound (US) pachymetry. RESULTS Each of the 3 groups comprised 50 eyes. There were no differences between the 3 groups in age, sex, or intraocular pressure. In normal eyes, CCT was statistically significantly higher by US pachymetry (mean 525.8 microm +/- 41.4) [SD] than by Scheimpflug imaging (mean 519.4 +/- 40.9 microm) and AS-OCT (mean 517.9 +/- 41.5 microm) (both P<.001). In keratoconus eyes, CCT by US pachymetry (mean 446.4 +/- 57.9 microm) was statistically significantly higher than by Scheimpflug imaging (mean 439.6 +/- 62.1 microm) (P = .002) and AS-OCT (mean 441.8 +/- 58.4 microm) (P = .007). In post-LASIK eyes CCT by US pachymetry (mean 462.4 +/- 44.7 microm) was significantly higher than by Scheimpflug imaging (mean 457.9 +/- 33.6 microm) (P = .012) and AS-OCT (mean 455.4 +/- 43.2 microm) (P<.001). In all groups, CCT measured by Scheimpflug imaging and AS-OCT was similar. CONCLUSIONS There was a statistically significant difference between Scheimpflug imaging and US pachymetry and AS-OCT, with US pachymetry measurements being consistently thicker. Thus, CCT should be interpreted in the context of the instrument used.
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Bühren J, Yoon G, MacRae S, Huxlin K. Contribution of optical zone decentration and pupil dilation on the change of optical quality after myopic photorefractive keratectomy in a cat model. J Refract Surg 2010; 26:183-90. [PMID: 20229950 DOI: 10.3928/1081597x-20100224-04] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2008] [Accepted: 03/11/2009] [Indexed: 11/20/2022]
Abstract
PURPOSE To simulate the simultaneous contribution of optical zone decentration and pupil dilation on retinal image quality using wavefront error data from a myopic photorefractive keratectomy (PRK) cat model. METHODS Wavefront error differences were obtained from five cat eyes 19+/-7 weeks (range: 12 to 24 weeks) after spherical myopic PRK for -6.00 diopters (D) (three eyes) and -10.00 D (two eyes). A computer model was used to simulate decentration of a 6-mm sub-aperture relative to the measured wavefront error difference. Changes in image quality (visual Strehl ratio based on the optical transfer function [VSOTF]) were computed for simulated decentrations from 0 to 1500 mum over pupil diameters of 3.5 to 6.0 mm in 0.5-mm steps. For each eye, a bivariate regression model was applied to calculate the simultaneous contribution of pupil dilation and decentration on the pre- to postoperative change of the log VSOTF. RESULTS Pupil diameter and decentration explained up to 95% of the variance of VSOTF change (adjusted R(2)=0.95). Pupil diameter had a higher impact on VSOTF (median beta=-0.88, P<.001) than decentration (median beta=-0.45, P<.001). If decentration-induced lower order aberrations were corrected, the impact of decentration further decreased (beta=-0.26) compared to the influence of pupil dilation (beta=-0.95). CONCLUSIONS Both pupil dilation and decentration of the optical zone affected the change of retinal image quality (VSOTF) after myopic PRK with decentration exerting a lower impact on VSOTF change. Thus, under physiological conditions pupil dilation is likely to have more effect on VSOTF change after PRK than optical zone decentration.
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Affiliation(s)
- Jens Bühren
- University of Rochester Eye Institute, University of Rochester Medical Center, Rochester, NY, USA.
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22
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McKelvie J, Ku JY, McArdle B, McGhee C. Wavefront aberrometry: Comparing and profiling higher-order aberrations produced by intraocular lenses in vitro using a physical model eye system and Hartman-Shack aberrometry. J Cataract Refract Surg 2009; 35:547-55. [DOI: 10.1016/j.jcrs.2008.11.048] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2008] [Revised: 11/04/2008] [Accepted: 11/07/2008] [Indexed: 11/26/2022]
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Wavefront-guided LASIK for Myopia: Effect on Visual Acuity, Contrast Sensitivity, and Higher Order Aberrations. J Refract Surg 2009; 25:524-33. [DOI: 10.3928/1081597x-20090512-06] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Alió JL, Piñero DP, Plaza Puche AB. Corneal wavefront-guided photorefractive keratectomy in patients with irregular corneas after corneal refractive surgery. J Cataract Refract Surg 2008; 34:1727-35. [DOI: 10.1016/j.jcrs.2008.06.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Accepted: 06/11/2008] [Indexed: 10/21/2022]
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Cheng ZY, He JC, Zhou XT, Chu RY. Effect of flap thickness on higher order wavefront aberrations induced by LASIK: a bilateral study. J Refract Surg 2008; 24:524-9. [PMID: 18494346 DOI: 10.3928/1081597x-20080501-11] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To investigate the effect of flap thickness on wavefront aberrations induced by LASIK. METHODS LASIK was performed on 56 eyes of 28 patients with refraction errors that were well matched between the right and left eyes. For each patient, a planned 160-microm flap was created for one randomly selected eye using the Moria M2 microkeratome (130-microm head; thick flap group), and a 110-microm flap was created for the contralateral eye with the same microkeratome (90-microm head; thin flap group). Flap thickness was measured using ultrasonic pachymetry. Wavefront aberrations were measured in the anterior cornea using the Orbscan II (Bausch & Lomb) and in the whole eye using the Wavefront Supported Custom Ablation (WASCA) aberrometer (Carl Zeiss Meditec) preoperatively and at 1 month and 1 year postoperatively. RESULTS Mean flap thickness was 155 +/- 13 microm in the thick flap group and 112 +/- 11 microm in the thin flap group. Mean root-mean-square of higher order wavefront aberrations were changed for the different test times in the cornea (F = 29.9, P < .0001) and the whole eye (F = 48.0, P < .0001). There was no significant difference between the two flap groups for the cornea (F = 0.76) or for the whole eye (F = 0.07). Similar results were observed for higher order Zernike aberrations such as spherical aberration and comas. CONCLUSIONS The results suggest higher order wavefront aberrations induced by LASIK are independent of flap thickness. Complications in visual outcome for patients with different flap thickness should be attributed to factors other than aberrations.
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Affiliation(s)
- Zhen-Ying Cheng
- Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China
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27
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Measurement of corneal curvature change after mechanical laser in situ keratomileusis flap creation and femtosecond laser flap creation. J Cataract Refract Surg 2008; 34:238-42. [DOI: 10.1016/j.jcrs.2007.09.023] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Accepted: 09/17/2007] [Indexed: 11/21/2022]
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Comparison of Corneal Aberration Changes After Laser In Situ Keratomileusis Performed With Mechanical Microkeratome and IntraLase Femtosecond Laser: 1-Year Follow-up. Cornea 2008; 27:174-9. [DOI: 10.1097/ico.0b013e31815a50bf] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Bühren J, Kohnen T. [Application of wavefront analysis in clinical and scientific settings. From irregular astigmatism to aberrations of a higher order--Part II: examples]. Ophthalmologe 2008; 104:991-1006; quiz 1007-8. [PMID: 18030477 DOI: 10.1007/s00347-007-1648-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In recent years, wavefront analysis has ceased to be purely a laboratory application and emerged as a method used in ophthalmological diagnosis. This development has been promoted mainly by the widespread use of wavefront-guided LASIK (laser in situ keratomileusis). However, aberrometry is still not a common diagnostic technique, and for many ophthalmologists interpretation of the results is difficult. The second part of this serial paper reviews findings that are relevant for the ophthalmological community and highlights current scientific applications in this area.
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Affiliation(s)
- J Bühren
- Advanced Physiological Optics Lab, Department of Ophthalmology, University of Rochester Medical Center, Rochester, NY, USA
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Bababeygy SR, Zoumalan CI, Manche EE. Visual outcomes of wavefront-guided laser in situ keratomileusis in eyes with moderate or high myopia and compound myopic astigmatism. J Cataract Refract Surg 2008; 34:21-7. [PMID: 18165076 DOI: 10.1016/j.jcrs.2007.08.032] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2007] [Accepted: 08/13/2007] [Indexed: 10/22/2022]
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Ahn JY, Kwon JW, Lee SM, Wee WR, Lee JH, Han YK. Comparison of the Flap Complication Rate Between Microkeratomes for LASIK. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2008. [DOI: 10.3341/jkos.2008.49.9.1425] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Jee Yun Ahn
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea
- Seoul Artificial Eye Center, Clinical Research Institute, Seoul National University Hospital, Seoul, Korea
| | - Ji Won Kwon
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea
- Seoul Artificial Eye Center, Clinical Research Institute, Seoul National University Hospital, Seoul, Korea
- Seoul National University Hospital, Health Care System Gangnam Center, Healthcare Research Institute, Seoul, Korea
| | - Sang Mok Lee
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea
- Seoul Artificial Eye Center, Clinical Research Institute, Seoul National University Hospital, Seoul, Korea
- Department of Ophthalmology, Seoul National University Boramae Hospital, Seoul, Korea
| | - Won Ryang Wee
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea
- Seoul Artificial Eye Center, Clinical Research Institute, Seoul National University Hospital, Seoul, Korea
| | - Jin Hak Lee
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea
- Seoul Artificial Eye Center, Clinical Research Institute, Seoul National University Hospital, Seoul, Korea
- Department of Ophthalmology, Seoul National University Bundang Hospital, Seongnam, Korea
| | - Young Keun Han
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea
- Seoul Artificial Eye Center, Clinical Research Institute, Seoul National University Hospital, Seoul, Korea
- Department of Ophthalmology, Seoul National University Boramae Hospital, Seoul, Korea
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Medeiros FW, Stapleton WM, Hammel J, Krueger RR, Netto MV, Wilson SE. Wavefront Analysis Comparison of LASIK Outcomes With the Femtosecond Laser and Mechanical Microkeratomes. J Refract Surg 2007; 23:880-7. [DOI: 10.3928/1081-597x-20071101-03] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Caster AI, Friess DW, Potvin RJ. Absence of Keratectasia After LASIK in Eyes With Preoperative Central Corneal Thickness of 450 to 500 Microns. J Refract Surg 2007; 23:782-8. [DOI: 10.3928/1081-597x-20071001-07] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Pepose JS, Feigenbaum SK, Qazi MA, Merchea M. Comparative performance of the Zyoptix XP and Hansatome zero-compression microkeratomes. J Cataract Refract Surg 2007; 33:1386-91. [PMID: 17662429 DOI: 10.1016/j.jcrs.2007.04.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2007] [Accepted: 04/03/2007] [Indexed: 10/23/2022]
Abstract
PURPOSE To compare flap parameters produced by the Zyoptix XP and Hansatome microkeratomes (both Bausch & Lomb) and to evaluate preoperative variables contributing to flap thickness variation. SETTING Private practice, St. Louis, Missouri, USA. METHODS Flap dimensions in 75 eyes that prospectively had laser in situ keratomileusis using the Zyoptix XP microkeratome were compared with a historical control sample of 75 eyes treated with the Hansatome microkeratome. The 2 groups were matched for mean keratometry, central corneal pachymetry, spherical equivalent (SE), age, and microkeratome head size and suction ring diameter. RESULTS The mean ultrasound-measured flap thickness was 126.54 microm +/- 14.6 (SD) and 143.74 +/- 15.0 microm for the 120 microm and 140 microm Zyoptix XP heads, respectively, and 128.90 +/- 20.4 microm and 143.32 +/- 21.0 microm for the 160 microm and 180 microm Hansatome heads, respectively. The standard deviation in flap thickness was smaller and statistically significant for the Zyoptix XP (+/-14.8 microm) versus the Hansatome (+/-20.7 microm) (P = .0039, F test). Preoperative pachymetry and SE (P<.001) accounted for 20% of the variability in measured flap thickness using the Hansatome. For the Zyoptix XP, preoperative pachymetry was statistically significant in explaining the variation in flap thickness with the 120 microm head (P = .02) but not with the 140 microm head. Variation in flap thickness from either Zyoptix XP head was not statistically related to the preoperative SE. CONCLUSION Although the 2 microkeratomes produced flaps of similar mean thickness, the Zyoptix XP showed significantly less variation in flap thickness than the Hansatome, was less affected by measurable preoperative variables such as SE, and was closer to nominal labeling.
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Li Y, Netto MV, Shekhar R, Krueger RR, Huang D. A Longitudinal Study of LASIK Flap and Stromal Thickness with High-speed Optical Coherence Tomography. Ophthalmology 2007; 114:1124-32. [PMID: 17320959 DOI: 10.1016/j.ophtha.2006.09.031] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Revised: 09/13/2006] [Accepted: 09/13/2006] [Indexed: 11/23/2022] Open
Abstract
OBJECTIVE To assess corneal anatomic changes after LASIK with a high-speed corneal and anterior segment optical coherence tomography (CAS-OCT) system. DESIGN Cross-sectional observational study. PARTICIPANTS Fifty-one eyes of 26 healthy persons undergoing LASIK. METHODS The CAS-OCT prototype operated at a 1.3-mum wavelength and 2000 axial scans/second. The corneas were scanned with a flap profile pattern (horizontal line, 512 axial scans) and a flap map pattern (4 radials, 256 axial scans each). Both patterns are 8 mm long and are centered on the corneal vertex. LASIK flaps were created using either a mechanical microkeratome (Hansatome; Bausch & Lomb, Inc., Rochester, NY) or a femtosecond laser (Pulsion; IntraLase Corp., Irvine, CA). Intraoperative pachymetry was performed using a 50-MHz ultrasound probe. Three OCT scans were obtained on preoperative and post-LASIK visits up to 6 months. An automated algorithm was developed to process the OCT images and to calculate corneal, flap, and stromal bed thickness profiles and maps. The profiles and maps were divided into central (diameter, <2 mm), pericentral (2-5 mm), and transitional (5-7 mm) zones for analysis. MAIN OUTCOME MEASURES Corneal, flap, and stromal bed thicknesses as determined by OCT and ultrasound pachymetry. RESULTS The flap interface was best detected in the pericentral zone. One week after surgery, the repeatability of OCT flap and stromal bed thickness measurement was 2 to 7 microm by pooled standard deviation for zones inside a 5-mm diameter. The central flap thickness in 24 Hansatome eyes with a 180-microm setting was 143+/-14 microm by OCT and 131+/-17 microm by ultrasound. In the 8 IntraLase cases with a 120-microm setting, it was 156+/-11 microm by OCT and 160+/-19 microm by ultrasound. Eyes with other settings also were analyzed. There were small systematic changes in flap thickness up to 1 week and bed thickness up to 3 months. CONCLUSIONS We have developed a method for using high-speed OCT to measure LASIK flap thickness after surgery. The measurement is noncontact, rapid, and repeatable. Profile and map measurements provide more information than point measurements previously demonstrated. This could be valuable for planning LASIK enhancement and characterizing microkeratome performance.
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Affiliation(s)
- Yan Li
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA
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Zhou C, Jin M, Wang X, Ren Q. Corneal Wavefront-guided Ablation With the Schwind ESIRIS Laser for Myopia. J Refract Surg 2007; 23:573-80. [PMID: 17598576 DOI: 10.3928/1081-597x-20070601-07] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate the outcome of corneal wavefront-guided LASIK for the treatment of myopia and myopic astigmatism. METHODS This study included 56 myopic virgin eyes of 28 patients with a mean spherical equivalent refraction of -4.40 +/- 1.83 diopters (D) (range: -1.25 to -9.75 D) and astigmatism < 2.50 D. The corneal wavefront aberrations were analyzed using a corneal topography system. The preoperative corneal wavefront aberration data obtained from the above analyses combined with manifest refraction were used to generate a customized ablation profile. The safety, efficacy, and predictability of the correction, contrast sensitivity, and corneal higher order wavefront aberrations were evaluated. RESULTS At 1-year follow-up, the mean residual spherical equivalent refractive error was -0.15 +/- 0.3 D (range: 0 to -1.25 D) and mean cylinder was -0.54 +/- 0.34 D (range: 0 to -1.50 D). Ninety-five percent of eyes were in the residual refractive error range of +/- 0.50 D and uncorrected visual acuity improved by 1.00 D or better in 94% of eyes. The safety index and efficacy index were 1.13 and 0.92, respectively. After treatment, corneal higher order wavefront aberrations with a 6-mm pupil diameter increased significantly (paired sample t test, P < .01), and contrast sensitivity with glare had small reductions at high spatial frequencies. Changes in spherical-like aberration (R = 0.708, P < .001) and higher order wavefront aberration (R = 0.449, P = .001), except for coma-like aberration (P = .238), were positively correlated with the amount of achieved correction. CONCLUSIONS Evaluation of clinical results showed that corneal wavefront-guided LASIK for the correction of myopia and myopic astigmatism was safe and effective. There was an increase in all higher order aberrations postoperatively.
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Affiliation(s)
- Chuanqing Zhou
- Laboratory of Ophthalmology & Visual Optics, Institute for Laser Medicine and Bio-Photonics, Department of Biomedical Engineering, College of Life Science and Technology, Shanghai Jiaotong University, Shanghai, China
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Abstract
PURPOSE To provide a summary of the methods used by clinical wavefront analyzers and their historical, current, and future applications. METHODS Review of the literature and authors' experience with the various devices. RESULTS A wide range of clinical wavefront aberrometers, which use different principles, are available to clinicians and researchers. CONCLUSIONS Applications of wavefront analyzers in vision sciences range from assessment of refractive error, refractive surgery planning, evaluation of outcomes, optimization of contact lenses and IOL designs, evaluation of pathology relating to optical performance of the eye, and evaluation of accommodation alterations.
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Affiliation(s)
- Alejandro Cerviño
- School of Life and Health Sciences, Aston University, Birmingham, United Kingdom
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de Benito-Llopis L, Teus MA, Sánchez-Pina JM, Hernández-Verdejo JL. Comparison Between LASEK and LASIK for the Correction of Low Myopia. J Refract Surg 2007; 23:139-45. [PMID: 17326353 DOI: 10.3928/1081-597x-20070201-06] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To compare the refractive results of laser epithelial keratomileusis (LASEK) and laser in situ keratomileusis (LASIK) for the correction of low myopia. METHODS A prospective, interventional, non-randomized, observer-masked study was performed of patients with myopia of < or = -2.50 diopters (D) (cylinder < or = 1.50 D) who had undergone either LASEK or LASIK. Refractive analysis was performed by a masked observer preoperatively and 1 day, 1 week, and 1 and 3 months postoperatively. RESULTS Seventy-nine eyes that fulfilled the inclusion criteria in each group were included in the study. No statistically significant differences were noted in age, gender, or preoperative refractive error between groups. Postoperative uncorrected visual acuity (UCVA) was significantly lower in LASEK eyes 1 and 7 days postoperatively (P = .0001). At 1 and 3 months postoperatively, no significant differences were noted between the groups in UCVA (P = .07), but best spectacle-corrected visual acuity 3 months postoperatively was significantly better in LASEK eyes (P = .01). The refractive error was similar in both groups (P = .3). CONCLUSIONS Visual improvement after LASEK for low myopia is significantly slower than after LASIK. Visual outcomes at 3 months postoperatively were similar with both techniques for the correction of low myopia.
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Gatinel D, Chaabouni S, Adam PA, Munck J, Puech M, Hoang-Xuan T. Corneal Hysteresis, Resistance Factor, Topography, and Pachymetry After Corneal Lamellar Flap. J Refract Surg 2007; 23:76-84. [PMID: 17269247 DOI: 10.3928/1081-597x-20070101-12] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To measure prospectively the early changes in corneal hysteresis, topography, and pachymetry after the creation of a stromal flap cut without laser photoablation. METHODS A 37-year-old man was referred for a bioptic procedure to correct for compound myopic astigmatism in the left eye. A 159-microm-thick 8x8.5-mm superior hinged flap was created with a mechanical microkeratome in the left cornea. Changes in the corneal hysteresis, corneal resistance factor, Goldmann correlated intraocular pressure (lOP), corneal compensated IOP, anterior and posterior topography, and optical and ultrasound pachymetry were monitored prospectively before and at 1 hour, 1 day, 5 days, and 25 days after flap creation. The right eye served as a control. RESULTS In the left eye, corneal hysteresis and corneal resistance factor decreased immediately after the flap cut and remained lower than preoperatively at 1 hour, 1 day, 5 days, and 25 days. Corneal compensated IOP varied significantly less than Goldmann correlated IOP in both eyes. Central flattening of the horizontal meridians was observed on the difference topography maps. The values of the left eye posterior best fit sphere increased after the flap cut. Increased central corneal thickness occurred immediately after the flap cut and decreased over time without returning to its preoperative value. CONCLUSIONS The creation of a stromal flap can modify the biomechanical properties of the cornea, including a reduction in corneal hysteresis. The topographic changes were consistent with previously reported cases of flap cut in normal corneas.
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Affiliation(s)
- Damien Gatinel
- Rothschild Foundation, 25 rue Manin, 75019 Paris, France.
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Awwad ST, Bowman RW, Cavanagh HD, McCulley JP. Wavefront-guided LASIK for Myopia Using the LADAR CustomCornea and the VISX CustomVue. J Refract Surg 2007; 23:26-38. [PMID: 17269241 DOI: 10.3928/1081-597x-20070101-06] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate the objective and subjective visual outcomes and refractive results of wavefront-guided LASIK with LADAR CustomCornea and VISX CustomVue. METHODS This prospective randomized single-institution multisurgeon study comprised 100 eyes of 58 patients (50 eyes on each laser platform). Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and manifest refraction were measured postoperatively at 1 day, 1 week, 1 month, and 3 months. Contrast sensitivity, higher order aberrations measurement, and a subjective vision questionnaire were performed preoperatively and at 3 months. RESULTS Preoperatively, the CustomCornea group had a mean manifest sphere of -3.58 +/- 1.61 diopters (D) (range: -0.50 to -7.25 D), cylinder of +0.64 +/- 0.45 D (range: 0 to +1.75 D), and manifest refractive spherical equivalent (MRSE) of -3.26 +/- 1.56 D. The CustomVue group had a manifest sphere of -4.00 +/- 1.69 D (range: -1.50 to -7.50 D), cylinder of +0.60 +/- 0.52 D (range: 0 to +2.00 D), and MRSE of -3.70 +/- 1.64 D. At 3 months, 94% of CustomCornea eyes and 84% of CustomVue eyes had UCVA > or = 20/20 (P = .20). Twenty-four percent of CustomVue eyes and 22% of CustomCornea eyes gained 1 line of BSCVA. In both groups, 96% of eyes were within 0.50 D of emmetropia. Mean CustomCornea glare contrast sensitivity improved (P = .04) whereas more eyes improved than worsened in both groups. Spherical aberration and total higher order aberrations increased, and trefoil decreased in both groups. A decrease in coma was noted in 70% of CustomCornea eyes. CONCLUSIONS Wavefront-guided LASIK with both platforms is safe, effective, and delivers excellent visual results. CustomCornea improves contrast sensitivity under glare conditions.
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Affiliation(s)
- Shady T Awwad
- Dept of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390-9057, USA
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Condon PI. 2005 ESCRS Ridley Medal Lecture. J Cataract Refract Surg 2006; 32:2124-32. [PMID: 17137995 DOI: 10.1016/j.jcrs.2006.07.036] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Accepted: 07/11/2006] [Indexed: 11/22/2022]
Abstract
The literature on keratoconus and progressive post-laser in situ keratomileusis ectasia (PPLK) was studied after a retrospective review of 137 highly myopic eyes (mean -15.58 diopters) 5 to 9 years after LASIK. Only 2 eyes developed keratectasia, 1 after automated lamellar keratolasty for myopia and 1 after myopic LASIK. In neither case was intraoperative pachymetry carried out. In the PPLK case, a residual stromal bed thickness (RSBT) of 120 microm was discovered when a retreatment was attempted on lifting the flap. The PPLK developed 2 years later. The obvious discrepancy between reported cases of PPLK and the expected rate from the incidences in larger retrospective studies and our own 15-year experience suggests that PPLK is not a significant complication provided the standard rules applying to the preoperative total corneal thickness and RSBT are observed. However, newer techniques for the study of posterior corneal changes and those involving corneal biomechanics should be used in the future to study the long-term effects of LASIK on the cornea.
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Awwad ST. Wavefront-guided ablation: evidence for efficacy compared to traditional ablation. Am J Ophthalmol 2006; 141:1169; author reply 1169. [PMID: 16765706 DOI: 10.1016/j.ajo.2006.03.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Accepted: 03/07/2006] [Indexed: 11/24/2022]
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Li Y, Shekhar R, Huang D. Corneal pachymetry mapping with high-speed optical coherence tomography. Ophthalmology 2006; 113:792-9.e2. [PMID: 16650675 PMCID: PMC1474520 DOI: 10.1016/j.ophtha.2006.01.048] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2005] [Revised: 01/31/2006] [Accepted: 01/31/2006] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To map corneal thickness before and after LASIK with optical coherence tomography (OCT). DESIGN Cross-sectional observational study. PARTICIPANTS Forty-two eyes of 21 normal subjects undergoing LASIK. METHODS A high-speed (2000 axial scans/second) 1.3-microm-wavelength corneal and anterior segment OCT prototype was used for corneal scanning. The scan pattern consisted of 10-mm radial lines on 8 meridians centered on the vertex reflection. The entire scan pattern of 1024 a-scans was acquired in 0.5 seconds. We developed automated computer processing for 3-dimensional corneal reconstruction and measurement. Corneal thickness was measured normal to the anterior surface and presented as color pachymetry maps and zonal statistics. The maps were divided into a central zone (<2 mm) and 3 annular areas (pericentral, 2-5 mm; transitional, 5-7 mm; peripheral, 7-10 mm), which were further divided into quadrantal zones. The average, minimum, and maximum corneal thicknesses were computed for zones within the 7-mm diameter. Optical coherence tomography and ultrasound pachymetry were measured 3 times at the preoperative and 3-month postoperative visits. Reproducibility was assessed by the pooled standard deviations (SDs) of the repeated measurements. MAIN OUTCOME MEASURES Optical coherence tomography pachymetric map and zonal statistic, and ultrasound pachymetry. RESULTS Before LASIK, central corneal thicknesses (CCTs) were 546.9+/-29.4 microm (mean +/- SD) for OCT and 553.3+/-33.0 microm for ultrasound. After LASIK, CCTs were 513.7+/-44.5 microm for OCT and 498+/-46.6 microm for ultrasound. Optical coherence tomography and ultrasound CCT were highly correlated (Pearson correlation r = 0.97 before LASIK and 0.98 afterwards). Optical coherence tomography CCT was slightly less than ultrasound CCT before surgery (mean difference, -6.4 microm; 95% limits of agreement, -23.2 to 10.4 microm) but slightly greater after LASIK (15.7 microm; -1.6 to 33 microm). These differences were statistically significant, but no more than the CCT measurement differences between ultrasound pachymeters. The reproducibility of the OCT zonal pachymetry averages was roughly 2 microm. CONCLUSIONS High-speed OCT provided noncontact, rapid, reproducible pachymetric mapping over a wide area of the cornea. It is equivalent to ultrasound for CCT measurement before and after LASIK. This technology could be valuable for planning keratorefractive procedures and diagnosis of corneal diseases.
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Affiliation(s)
- Yan Li
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio
| | - Raj Shekhar
- Department of Biomedical Engineering, Cleveland Clinic Foundation, Cleveland, Ohio
| | - David Huang
- Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio
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Affiliation(s)
- Shady T Awwad
- University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
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