The aging eye - how does vision change as one grows older?
The human visual system deteriorates throughout adult life. This is quite normal. The visual system is often characterized as "young" until it reaches about 40 years of age. After that, normal changes to the aging eye become more noticeable as visual capabilities decrease.
- Reduced accommodation (Presbyopia) - This is the eye's decreasing capacity to focus at close range. Hardening of the crystalline lens capsule and, perhaps, atrophy of the ciliary muscles are the primary causes of lost accommodation. This process is continuous with age, but by age 45 most people require positive diopter lenses (reading glasses) for close work. By age 65, variable accommodation is nearly impossible and multi-focal lenses are required.
- Reduced retinal illuminance - The retina receives less light as one ages because pupil size becomes smaller (senile miosis) and the crystalline lens becomes thicker and more absorptive. It is estimated that for the same light level, a typical 60-year old receives about one-third the retinal illuminance of a 20-year old.
- Reduced contrast and color saturation - The crystalline lens becomes less clear and, as a result, begins to scatter more light as one ages. This scattered light reduces the contrast of the retinal image. This effect also adds a "luminous veil" over colored images on the retina, thus reducing their vividness (saturation). Reds begin to look like pinks, for example.
- Reduced ability to discriminate blue colors - The older eye loses some sensitivity to short wavelengths ("blue light") due to progressive yellowing of the crystalline lens.