Methods of estimating corneal refractive power after hyperopic laser in situ keratomileusis

Abstract

Purpose: To evaluate and compare methods of estimating corneal refractive power after hyperopic laser in situ keratomileusis (LASIK). Setting: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. Methods: Using the clinical history method (HisRP) as the standard, the accuracy of values of corneal refractive power derived from the EyeSys Corneal Analysis System or Humphrey Atlas computerized videokeratography, the thin lens formula, and corneal topographic measurements modified according to the amount of LASIK-induced refractive change were evaluated. Results: Thirty-four eyes of 19 patients were evaluated using EyeSys and 27 eyes of 16 patients were examined using Humphrey Atlas. Although the values derived from corneal topography and the thin lens formula correlated well with HisRP, the differences between HisRP and topographic values increased significantly with increasing hyperopic correction. When the values of corneal topographic measurements were modified according to the amount of LASIK-induced refractive change, the accuracy was significantly improved (all P < .05) and the percentages of eyes within 0.5 diopter (D) and 1.0 D of the HisRP values exceeded 71% and 94%, respectively. Conclusion: Using the clinical history method as the standard, the most accurate method for determining corneal refractive power in hyperopic LASIK eyes was to adjust the postoperative corneal topographic measurement according to the amount of LASIK-induced refractive change.