The human eye as a robust optics system

Pablo Artal
University of Murcia

In most eyes, the resolution capabilities of the eye’s optics and the retinal mosaic are remarkably well adapted. Although there is a large individual variability, the average magnitude of the high order aberrations is similar in group of eyes with different refractive errors. This is surprising since these eyes are comparatively different in shape: myopic eyes are longer while hyperopic eyes are shorter. In most young eyes, the amount of aberrations for the isolated cornea is larger than for the complete eye, indicating that the internal ocular optics (mainly the crystalline lens) play a significant role in compensating for the corneal aberrations, thereby producing an improved retinal image. Spherical aberration of the cornea is partially compensated by that of the lens in most eyes. Lateral coma is also compensated mainly in hyperopic eyes. The distribution of aberrations between the cornea and lens appears to allow the optical properties of the eye to be relatively insensitive to variations arising from eye growth or exact centration and alignment of the eye’s optics relative to the fovea. There is an auto-compensation mechanism that renders the eye’s optics robust despite large variation in the ocular shape and geometry.
Other compensatory mechanisms will be also described, i.e., those for the peripheral retina of the movements of the crystalline after saccadic eye movements.

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