Abstract
Purpose :
Stereoacuity deterioration following keratorefractive surgeries is attributed to an increase in the magnitude and interocular differences in post-operative higher-order aberrations (HOAs) (Sarkar et al, 2020). This study modeled the contributions of interocular HOA differences induced by refractive surgery to disparity visibility and binocular matching using cross-correlation analyses.
Methods :
We recruited subjects (n=99) with myopia and astigmatism ≤1.5 D who underwent Femtosecond Laser-Assisted In situ Keratomileusis (FS-LASIK, n=38), PhotoRefractive Keratectomy (PRK, n=26) or SMall-Incision Lenticule Extraction (SMILE, n=35). Post-cycloplegic HOAs and stereoacuities were measured for 6mm diameter pupils pre-operatively, and 1, 4, 12 and 24 weeks post-operatively. Left and right eye retinal image pairs were convolved with respective HOA-derived point spread functions. Optical effects on disparity signal quality were modeled computationally using four metrics derived from binocular cross-correlation functions, namely, signal width, signal height, signal-to-noise ratio, and height-to-width ratio (Metlapally et al, 2019). We assessed covariation of cross-correlation metrics with corresponding psychophysical measures of stereoacuity. We also compared the three refractive surgeries for their binocular outcomes using analyses of variance.
Results :
Increased interocular average and difference in the magnitude of HOAs caused sustained worsening of stereoacuity (Sarkar et al, 2020). Stereoacuity strongly covaried with the four cross-correlation metrics (p<0.001, r=0.725, -0.630, -0.732 and -0.786, respectively, for the four metrics above). The changes from the pre-operative to the 24-week time point for each of the cross-correlation metrics differ significantly among the three refractive surgeries. Altogether, SMILE showed better binocular outcomes than LASIK or PRK (p<0.001).
Conclusions :
Mismatched HOAs add disparity noise by differentially altering the properties of the retinal images of the two eyes, and negatively affect binocular matching and disparity visibility. Computational analyses point to disparity noise as a possible mechanism through which HOAs induced following refractive surgery make extracting stereoacuity difficult. They also suggest better binocular outcomes for SMILE than LASIK or PRK.
This is a 2021 ARVO Annual Meeting abstract.