Aging Effects on the Optics of the Eye

Different factors contribute to the increase in optical aberrations with age: possible modifications in the aberrations of the cornea, the lens, or even their relative contributions. The aberrations associated with the anterior surface of the cornea slightly change with age in a normal population, but the aberrations of the crystalline lens change due to the continuous modification of the lens shape with age. As the lens grows, its dimensions, curvatures, and refractive index change, altering the lens aberrations. Glasser and Campbell found a large change in the spherical aberration of excised older lenses measured in vitro. Another important factor to be considered is the nature of aberration coupling within the eye. It was shown that, in young subjects, the lens tends to compensate part of the corneal aberrations to produce an improved retinal image. As the aberrations of the lens change with age, it is quite plausible that this compensation is partially or completely lost. This explains the overall increase in aberration and the reduction of retinal image quality throughout the life span. This chapter will review the current ideas on the change of ocular aberrations with age and the possible impact this will have on the design of some ophthalmic devices, such as intraocular lenses.