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CJ Roberts, AM Mahmoud, EE Herderick, G Chan, W Li; Characterization of Corneal Topography after LASIK, as a function of Level of Correction . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3946.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Examine surgically-induced corneal shape changes and relate them to a biomechanical model of corneal response to LASIK. Methods: A retrospective study was performed of 2380 eyes of 1255 patients after a myopic LASIK procedure (Technolas 217) at the Hong Kong Sanatorium and Hospital. Patients received pre-op and 6 months post-op Orbscan (version 2.0) exams. The cornea was divided into three regions for analysis: central (2.5mm radius), mid-peripheral (2.5-3.25mm radius), and peripheral (3.25-4.5mm radius). Pre-op maps were subtracted from post-op maps and then regional differences were statistically analyzed by level of myopic correction in the following intervals: 0-2 diopters (D) (n=25), 2-4D (n=321), 4-6D (n=635), 6-8D (n=622), 8-10D (n=465), and ≷10D (n=311). Results: Significant (p<0.0001) decreases in average central pachymetry, as well as anterior curvature and elevation were observed in all groups, as expected. Significant increases (p<0.0001) were observed in average peripheral curvature (circumferentially for levels of correction greater than 2 D) and pachymetry (in the horizontal meridian and higher corrections only). Central posterior elevation demonstrated significant increases (p<0.05) only for greater than 4 D myopic corrections, with greater increases in higher corrections. Conclusion: Posterior shape changes increase with increasing level of correction and thus depth of ablation. Peripheral increases in pachymetry were observed in the transition zone where ablation had occurred. Anterior shape and pachymetry changes are consistent with the proposed biomechanical model.
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