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T. Ueda, Y. Nawa, K. Masuda, Y. Hara, H. Uozato; Posterior Corneal Surface Changes After Hyperopic Laser in situ Keratomileusis (H–LASIK) . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2749.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate the posterior corneal surface topographic changes after hyperopic LASIK (H–LASIK) using Orbscan. Methods: For 25 eyes of 15 patients who had undergone H–LASIK, we measured the posterior corneal surface with slit–scanning corneal topography (Orbscan I) preoperatively and at one year postoperatively. We took the center as a fit zone and calculated posterior corneal surface changes at 4 points: the nasal, temporal, superior, and inferior side in the 5.0–mm diameter. The posterior corneal topographic changes were analyzed using analysis of variance (ANOVA). Furthermore, the post/preoperative magnification ratio of the posterior corneal surface was calculated in a theoretical eye model. Results: When a reading "+" was defined as the forward displacement and "–" was defined as the backward displacement, the posterior corneal topographic changes were –2.8 ± 27.9 µm at the nasal side, –4.5 ± 27.8 µm at the temporal side, –3.9 ± 20.1 µm at the superior side, and –2.3 ± 20.1 µm at the inferior side. The posterior corneal surface between any two examined points showed no significant difference after H–LASIK. In addition, the hypothetical change of the posterior cornea was –8.3 µm after +3.0 D H–LASIK, which was approximately closer to our results. Conclusions: Clinical measurement of the posterior corneal displacement after H–LASIK with Orbscan revealed a backward shift. This change corresponded to our hypothetical artifactual changes with Orbscan, that is, changes in the magnification ratio.
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