Comparison of Corneal Power Calculation by Standard Keratometry and Total Keratometry in Eyes With Previous Myopic FS-LASIK.

Abstract

To compare the accuracy of Total Keratometry (TK) and standard keratometry (K) with the IOLMaster 700 (Carl Zeiss Meditec) in evaluating the corneal refractive change in eyes with previous myopic femtosecond laser-assisted LASIK (FS-LASIK). A series of consecutive patients who had undergone myopic FS-LASIK was prospectively enrolled. The refractive change in spherical equivalent (ΔSE) was defined as the difference between the preoperative target correction entered into the laser software and the postoperative cycloplegic refraction. The difference between the postoperative and the preoperative K (ΔK) and the difference between the postoperative and the preoperative TK (ΔTK) were compared to the ΔSE. Only the right eye of each patient was selected for the statistical analysis. Twenty-five eyes of 25 patients were enrolled. The mean ΔSE was -4.41 ± 1.68 diopters (D). The mean ΔK (-3.82 ± 1.60 D) revealed a statistically significant underestimation of the laser-induced refractive change (P < .0001), whereas the mean ΔTK (-4.36 ± 1.78 D) did not show any significant difference (P = .45). The difference between ΔK and ΔTK was statistically significant (P < .0001). Linear regression between the laser-induced refractive change and the individual difference between the postoperative K and TK disclosed a statistically significant relationship (r = -0.6930, r2 = 0.4803, P < .0001), thus revealing that higher refractive corrections increase the difference between the postoperative values of K and TK. TK does not underestimate the laser-induced corneal changes and can be considered a reliable option for intraocular lens power calculation after myopic excimer laser surgery. [J Refract Surg. 2021;37(12):848-852.].