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SPECIFIC CHANGES WITH AGING: VISION
The eye is a marvelously complex organ, made up of a series of structures that work together to ensure that the best possible image arrives at its protected interior. The retina, the eye\'s insulated back rim, is the site of nerve endings that transform light waves into the nerve impulses carried to the brain.
As we get older, Changes in several external structures cause less light to reach the retina. This dimming does not matter much in bright light, but it does matter when we need all the light we can get - in darkness. So the average person in his or her seventies tends to see well enough on a sunny day but has noticeably more difficulty seeing at night. Dim light is gloomier; a dark night appears pitch black.
One reason less light gets to the retina is that the lens, a clear structure toward the middle of the eye, gradually becomes cloudier over the years. This clouding also makes seeing m intense light more difficult; we are more likely to be blinded when a beam of light shines too directly at us. (To understand why a cloudy lens magnifies this blinding effect called glare, think what happens when you look through a slightly dirty windowpane while the sun is pouring in.)
Another change in the lens is the reason people often need bifocals by middle age. The lens is the eye\'s focusing apparatus. When it bends, we can see nearby objects; when it straightens out, we see objects farther away. Beginning in childhood, the lens becomes less and less flexible. This loss of flexibility means that by middle age almost everyone has more difficulty seeing close objects, and shifting one\'s gaze becomes more difficult. As we reach our fifties, it takes more time for objects at differing distances to come into focus.
This greater trouble in shifting gaze tends to be exacerbated by another aging change. The gray rim that develops around the pupil by our sixties causes a slight loss in peripheral vision: we cannot see quite as well as before out of the corners of our eyes.
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GENERAL HEALTH
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