Is “Whole Eye” Wavefront Analysis Helpful to Corneal Refractive Therapy?

Abstract

To examine how corneal refractive therapy (CRT) affects the balance between corneal surface and whole eye spherical aberration (Z4) and to identify whether corneal aberrations alone can accurately predict optical outcomes of CRT. Whole eye and corneal spherical aberrations were measured at baseline and 1 month after CRT in 12 dilated eyes (baseline myopia range, -2.25 to -6.00 diopters [D]; mean, -3.23 +/- 1.06D). Whole eye aberrations were measured under cycloplegia using a Shack-Hartmann aberrometer, and corneal aberrations were measured using Keratron corneal topography elevation maps converted to wavefront Zernike polynomials using VOL-CT. Whole eye and corneal surface aberrations were scaled for 6-mm pupil diameters. No statistically significant correlation existed between corneal and whole eye spherical aberration at baseline. Corneal and whole eye spherical aberration increased in all eyes after CRT. A statistically significant and moderately positive correlation was found between corneal and whole eye spherical aberration after CRT (R = 0.632, P = 0.004). The linear regression slope was positive (m = +1.449) and indicated that whole eye spherical aberration exceeds corneal spherical aberration after CRT. Whole eye wavefront analysis is essential to methods designed to optimize visual performance with CRT; results indicate that CRT affects the entire optical system and not just the anterior corneal surface. Moreover, because CRT-induced whole eye spherical aberration cannot be explained by corneal aberrations alone, commonly accepted beliefs that the mechanism of action is limited to corneal tissue redistribution may need to be revisited.