Alteration in corneal topography asymmetry indices following corneal refractive surgery

Abstract

Purpose We aimed to follow up corneal refractive asymmetry index changes following refractive surgery for cornea after correction of low-grade myopia and to determine which technique causes marked affection of the indices. Patients and methods This prospective study conducted from October 2020 to December 2021 included two groups of patients, the photorefractive keratectomy (PRK) group and the laser in-situ keratomileusis (LASIK) group. Every patient in each group had to follow a schedule of visits after surgery for the next day, 1 week, 1 month, and after 3 months. Patients who failed to follow this schedule were excluded from the study. Results The PRK group contained 42 eyes with a mean uncorrected visual acuity that improved significantly, corneal power (K-reading) and pupil center thickness reduced significantly. Surface variance index, central keratoconus index, and height decentration index did not change significantly. Vertical asymmetry index and minimum radius of curvature (Rmin) increased significantly while height asymmetry index decreased significantly. Our LASIK group contained 40 eyes that underwent changes similar to those in the PRK group regarding uncorrected visual acuity, the K-reading, and the pupil center thickness. The surface variance index, vertical asymmetry index, and height asymmetry index, height decentration index and Rmin increased significantly while the central keratoconus index decreased significantly. The keratoconus index reduced significantly in both groups. Conclusion The PRK is a more conservative technique than the LASIK technique regarding the affection of corneal asymmetry indices.

Keywords

• corneal indices
• laser in-situ keratomileusis
• myopia
• photorefractive keratectomy
• uncorrected visual acuity