Eyes

A change in vision is often the most undeniable sign of aging. Between the ages of 40 and 50, most people notice that seeing objects closer than 2 feet becomes difficult. This change in vision, called presbyopia, occurs because the lens in the eye stiffens. Normally, the lens changes its shape to help the eye focus. When the lens stiffens, the eye cannot easily focus on objects that are close.

Many people try to ignore presbyopia for as long as they can. But ultimately, almost everyone with presbyopia ends up wearing reading glasses. People who need glasses to see distant objects may need to wear bifocals or glasses with variable-focus lenses.

As people continue to age, vision changes in other ways. Seeing in dim light becomes more difficult. This change occurs because the lens tends to become denser. Light passes through the lens to the retina at the back of the eye. A denser lens means that less light enters the eye. Also, the retina, which contains the cells that sense light, becomes less sensitive. So for reading, brighter light is needed. On average, 60-year-olds need 3 times more light to read than 20-year-olds.

With aging, the pupil of the eye reacts more slowly to changes in light. Light enters the eye through the pupil, which widens or narrows to let more or less light in. Consequently, older people may be unable to see when they first enter a dark room. Or they may be temporarily blinded when they enter a brightly lit area. This effect is particularly bothersome when a person enters or leaves a dark movie theater or drives in or out of a dark tunnel. Older eyes are less able to adjust partly because the muscles that widen and narrow the pupils tend to weaken as people age. Older people may also become more sensitive to glare (bright light that shines directly or is reflected into the eyes). However, increased sensitivity to glare is usually due to an eye disorder, such as cataracts.

Colors are perceived differently as people age. This change occurs partly because the lens tends to yellow slightly with aging. Yellowing affects how colors at the blue-violet end of the light spectrum are seen. Blues tend to lose their vividness and look more like gray. This change is insignificant for most people. However, older people may have trouble reading black letters printed on a blue background or reading blue letters. At the other end of the spectrum, reds tend to appear more vivid.

The ability to see differences in shades and tones and to see fine details decreases. This change probably occurs because the number of nerve cells that transmit visual signals from the eyes to the brain decreases. This change affects the way depth is perceived, and judging distances becomes more difficult.

Older people may see more tiny black specks moving across their field of vision. These specks, called floaters, are bits of fluid within the eye that have solidified. Floaters do not significantly interfere with vision. Unless they suddenly increase in number, they are not a cause of concern.

Many older people are bothered by dry eyes. This change occurs because the number of cells that produce fluids to lubricate the eyes decreases. In some older people, tear production decreases.

The appearance of the eye may change. The whites (sclera) of the eyes may turn slightly yellow or brown. This change results from many years of exposure to ultraviolet light, wind, and dust. Random splotches of color may appear in the whites of the eyes. They are more common among people with a dark complexion. A gray-white ring (arcus senilis) may appear on the surface of the eye. The ring is made of calcium and cholesterol salts. It does not affect vision. The lower eyelid may hang away from the eyeball because the muscles that close the eye tend to weaken and the tendons that hold the eyelid in place stretch. The eye may appear to sink into the head because the amount of fat in the area around the eye decreases.

The serious eye problems that tend to occur during old age are caused by a disorder, not by aging itself. Examples are glaucoma, retinopathy, macular degeneration, and cataracts.