On the symmetry between eyes of wavefront aberration and cone directionality

There are two optical processes that control the retinal image sampled by the photoreceptor array: aberrations of the ocular optics and cone directionality (Stiles-Crawford effect). The shape of wavefront aberration and Stiles-Crawford functions are known to vary markedly across subjects. In this study we investigate in twelve subjects the symmetry between right and left eyes of wavefront aberration (measured using a spatially resolved refractometer) and cone directionality (measured using an imaging reflectometric technique). The pattern of aberrations is in general non-symmetric, suggesting that the development of aberrations follow independent paths in many right and left eye pairs. Cone directionality is in most cases mirror-symmetric (with one case of direct symmetry), suggesting some systematic process underlying cone orientation. Except in two subjects, symmetry in these two functions seems to be unrelated. Cone directionality apodization improves optical quality, but not optimally in all eyes, and it does not tend to increase symmetry in the optical performance of left and right eyes.