As we age the areas of the brain that interpret signals from the optic nerve are affected, which contributes to the decrease in visual acuity. Visual acuity may also be decreased by local changes in the eye itself. The retina can be damaged by atherosclerosis of itsvessels, a condition that may be worsened by diabetes. The retina may also be damaged by glaucoma. In this asymptomatic condition the pressure of fluid rises inside the eyeball. Because such an increase in pressure is slow and usually occurs without any symptoms initially, it is wise to have the eye-pressure checked at regular intervals.
Degeneration of the ligaments of the ciliary muscles that allow the lens to change its shape are another facet of the aging process, as is the gradual stiffening of the lens material so that it cannot easily alter shape, and so focus. Where shortsightedness was a problem in youth, farsightedness may become a problem in old age. Spectacles may be needed for close-up work and for other activities as we get older. Opacity of the lens of the eye is called a cataract. Surgery can remove the opaque lens, improving the sight, and special glasses help further.
Skin and hair
Aging skin atrophies and loses some of its normal properties. An additional factor is sunlight: excessive sun – or a passion for suntanning when young – is likely to give a prematurely wrinkled and aged skin. The wrinkles of people such as farmers and fishermen, who work outdoors in the elements for their living, provide evidence of this. The greying or whitening of hair is the result of tiny air bubbles appearing in the hair shaft. Although some claim to have turned grey over night, this is not possible because the process can start only at the root of the hair.