Aging Changes in the Human Accommodative Process

Accommodation, the process by which the human eye focuses on near objects, takes place through carefully controlled changes of the crystalline lens in shape, thickness, and anterior surface location relative to the cornea. These changes, which involve an elastic recovery of the lens upon accommodation from the maximally stressed and flattened non-accommodated lens shape, are coupled with the contraction of the ciliary muscle, which itself changes in shape and location relative to fixed points within the globe. The refractive range over which accommodation can occur is age-dependent. In youthful eyes, the range can be as great as 15 diopters, but the near point recedes steadily with increasing age in the adult eye until, by about 50 yr, it closely approaches the far point. This diminution in accommodative range is accompanied by other aging changes in the lens, ciliary muscle, and anterior segment geometry.