Accuracy of Orbscan total optical power maps in detecting refractive change after myopic laser in situ keratomileusis

Abstract

Purpose: To determine whether the refractive change obtained using the Orbscan-derived total optical power (TOP) map is in concordance with the manifest refractive change produced by laser in situ keratomileusis (LASIK). Setting: LASIK Vision Canada, Vancouver, BC, Canada (an ambulatory surgical center for refractive surgery). Methods: Twenty eyes of 10 consecutive bilateral LASIK patients were included in the study. Orbscan topographical analysis and manifest refraction were performed preoperatively and at least 1 month postoperatively. The change in manifest refraction (corrected to the corneal plane) before and after LASIK was correlated with the corneal power change averaged within the 2.0, 3.0, 4.0, and 5.0 mm diameter zones of TOP and axial power maps. Results: The central 4.0 mm zone TOP map gave the best correlation between manifest refractive change and Orbscan-measured corneal power change (r2= 0.835, P < .004). The correlation was higher with TOP maps than with anterior axial power maps. Conclusion: The corneal power change measured by the Orbscan TOP maps correlated highly with the changes in manifest refraction after LASIK.