Correlation Between Corneal and Total Wavefront Aberrations Measured at Various Optic Zones Pre– and Six Month Post–LASIK

Abstract

Abstract: : Purpose:To analyze the correlation between corneal and total wavefront aberrations at various optic zones (OZs) before and after LASIK. Methods: Thirty–one eyes of 20 myopic– astigmatic patients (–1.25D to –7.125D) that underwent LASIK were measured using the Oculus corneal topographer and a Tscherning–type wavefront analyzer pre–operatively and 6 month post–op. Corneal and total wavefront aberrations (WFA) were calculated up to the 6^th Zernike order and the high–order aberrations’ root mean square (RMS) was calculated in the same reference plane. Results:There was significant correlation (P<0.05) between the LASIK induced corneal aberrations and the total WFA for coma–like aberration at 3^rd (OZs 5>4>6), 4^th (OZs 5>6>4), 6^th (OZs 5>6>4) order Zernike coefficients, for spherical aberrations at all OZ’s (5>6>4) and for total WFA RMS (OZ’s 5>6>4). The fraction of LASIK induced total WFA atributed to the cornea was largest for OZ=5. We also found a strong correlation between the LASIK induced change in the RMS of high–order WFA (OZ=5mm) and the changes in corneal topography’s keratoconus index, Q–mean value and mean keratometry. Conclusions: Some LASIK induced aberrations in the mid periphery (4–6mm), such as coma and spherical, are mostly of corneal origin while others are not. Thus, ideal customized ablations algorithms must take both corneal and total wavefront aberrations into consideration.

Keywords: refractive surgery: LASIK • refractive surgery: corneal topography • refractive surgery: optical quality