The human eye is an example of robust optical design.
In most eyes, in the fovea and at best focus, 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 groups of eyes with different refractive errors. This is surprising because these eyes are comparatively different in shape: Myopic eyes are longer whereas 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. In this paper, we show that this compensation is larger in the less optically centered eyes that mostly correspond to hyperopic eyes. This suggests a type of mechanism in the eye's design that is the most likely responsible for this compensation. 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. We found that 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. These results may suggest the presence of an auto-compensation mechanism that renders the eye's optics robust despite large variation in the ocular shape and geometry.
Artal
Pablo
P
Departamento de Física, Universidad de Murcia, Campus de Espinardo, Murcia, Spain. pablo@um.es
Benito
Antonio
A
Tabernero
Juan
J
D000222:Adaptation, Physiological; D000328:Adult; D019781:Corneal Topography; D006801:Humans; D006956:Hyperopia / Q000503:physiopathology*; D007908:Lens, Crystalline / Q000503:physiopathology*; D009216:Myopia / Q000503:physiopathology*; D055095:Optics and Photonics; D012029:Refraction, Ocular; D012160:Retina / Q000503:physiopathology