Comparison of higher order monochromatic aberrations in amblyopic and non–amblyopic eyes

Abstract

Abstract: : Purpose:The phenomenon of aliasing in amblyopia is generally ascribed to neural undersampling. While optical quality in amblyopia appears normal the incidence of anisometropia suggests that the presence of amblyopia can influence optical development. The purpose of this study is to compare higher order monochromatic aberrations in normal and amblyopic eyes. Methods:15 subjects (mean age 21.50±2.88) with amblyopia participated with informed consent in the study. All subjects were students at Glasgow Caledonian University. The subjects underwent a full refractive and binocular examination which revealed the group to be composed of 2 strabismic, 6 anisometropic and 7 mixed amblyopic subjects. Mydriasis and cycloplegia were induced using 2 drops of 1.0% Tropicamide in each eye. Wavefront aberration was measured in both eyes of the subjects using the Zywave II Aberrometer (Bausch & Lomb) and measurement of right and left eyes was randomized. The Zywave II uses the Hartmann–Shack principle to determine the wavefront aberration which is then expressed in Zernicke polynomials up to and including the fifth order. Results:No significant difference was found in the total RMS error (calculated for the third to fifth order aberrations) between non–amblyopic and amblyopic eyes. Analysis of individual Zernicke coefficients revealed a significantly greater (p<0.01) Trefoil Y coefficient in the amblyopic eyes. No significant differences between non–amblyopic and amblyopic eyes were found for spherical aberration, coma or any of the other Zernicke coefficients. Conclusions:The results of the present study find no difference in higher order monochromatic aberrations between non–amblyopic and amblyopic eyes. This finding was despite the majority of subjects having clinically significant anisometropia. This would suggest that while amblyopia is often correlated with the development of abnormal refractive error it has no relationship with the development of higher order monochromatic aberrations.

Keywords: amblyopia • optical properties