Corneal curvature, asphericity, and aberrations after transepithelial photorefractive keratectomy and femtosecond laser-assisted in situ keratomileusis for myopia: A prospective comparative study

Abstract

Purpose: We aimed to compare transepithelial photorefractive keratectomy (TPRK) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for myopia treatment by analyzing corneal curvature, asphericity (Q-value), and corneal aberration.

Methods: Corneal topography was measured before and 6 months after the TPRK or FS-LASIK surgery. We measured and compared corneal curvature (sagittal curvature in the 1- to 7-mm zones), change in keratometric measurements (Kmpost - Kmpre, ΔK), Q-values (from the vertex of the 6-, 7-, 8-, and 9-mm zones), higher-order aberration (HOA), vertical and horizontal trefoil (Z3^-3 and Z3³), vertical and horizontal coma (Z3^-1 and Z3¹), and spherical aberration (Z4⁰) between the two surgery groups.

Results: The sagittal curvature Δ K in the 1-mm zone after TPRK was significantly higher than after FS-LASIK. The Δ K/ΔSE (ΔSE [spherical equivalent] = SEpre - SEpost) ratio in the 1- to 4-mm diameter zones was significantly higher after TPRK than after FS-LASIK. The preoperative Q-values of the 6- and 7-mm zones did not differ between the treatment groups, but postoperative values were significantly higher following FS-LASIK than following TPRK. HOA, Z4⁰, and Z3^-1 were all significantly higher after surgery in both groups. Postoperative Z3^-3 was significantly higher following TPRK but not following FS-LASIK. There were no postoperative differences in aberrations in either group; however, the change in HOA and Z3^-1 was significantly greater following FS-LASIK.

Conclusion: TPRK changes the corneal curvature to a greater extent and the visual quality (Q-value, aberrations) to a lesser extent than FS-LASIK.

Keywords: Asphericity; corneal aberrations; corneal curvature; corneal topography; femtosecond laser-assisted in situ keratomileusis (FS-LASIK); keratometry; myopia; sagittal curvature; transepithelial photorefractive keratectomy (TPRK).