| A cataract is a clouding of the normally clear eye lens. Clouded vision can make it more difficult to read, but commonly affect distance vision and cause problems with glare. They generally don't cause pain. Clouding of the lens is a normal part of getting older. About half of Americans older than 65 have some degree of cataract. After age 75, as many as 70 percent of Americans have impaired vision from cataracts. Most cataracts develop slowly and don't disturb eyesight early on. In the early stages, stronger lighting and eyeglasses can help, but at some point, if impaired vision jeopardizes lifestyle, one could need surgery. Fortunately, cataract removal is one of the safest, most effective of surgical procedures. Symptoms of a cataract include:
Cataracts don't typically cause any change in the appearance of your eye and isn't dangerous to the physical health of your eye unless the cataract becomes completely white, a condition known as an overripe (hypermature) cataract. This can cause inflammation, pain and headache. A hypermature cataract is extremely rare and needs removal as soon as possible. A cataract can develop in one or both eyes, and it may or may not affect the entire lens. The lens consists of three layers. The outer layer (capsule) is a thin, clear membrane. It surrounds a soft, clear material (cortex). The hard center of the lens is the nucleus. If you think of the lens as a piece of fruit, the capsule is the skin, the cortex is the fleshy fruit and the nucleus is the pit. A cataract can form in any part of the lens. Cataracts occur in three types: Nuclear. A nuclear cataract occurs in the center of the lens. In its early stages, as the lens changes the way it focuses light, one may become more nearsighted or even experience a temporary improvement in reading vision. Some people actually stop needing their glasses. Unfortunately, this so-called second sight disappears as the lens gradually turns yellow or greenish and begins to cloud vision. Cortical. A cortical cataract begins as whitish, wedge-shaped streaks on the outer edge of the lens cortex. As it slowly progresses, the streaks extend to the center and interfere with light passing through the nucleus. Both your distance and near vision can be impaired. Subcapsular. A subcapsular cataract starts as a small, opaque area just under the capsule shell. It usually forms at the back of the lens, right in the path of light on its way to the retina. This type of cataract may occur in both eyes but tends to be more advanced in one eye than the other. A subcapsular cataract often interferes with reading vision, reduces vision in bright light and causes glare or halos around lights at night. As we age the lenses in your eyes become less flexible, less transparent and thicker. The composition of the lens undergoes changes and the structure of the protein fibers breaks down. Some of the fibers begin to clump together, clouding small areas of the lens. As the cataract continues to develop, the clouding becomes more dense and involves a greater part of the lens. Doctors don't know why a lens changes with age, though one possibility is damage caused by unstable molecules known as free radicals. Smoking and exposure to UV light are two sources of free radicals. Age-related changes in the lens aren't the only cause of cataracts. Some people are born with cataracts or develop them during childhood. Such cataracts may be the result of the mother having contracted rubella (German measles) during pregnancy. They may also be due to metabolic disorders. Risk factors Everyone is at risk of developing cataracts simply because age is the single greatest risk factor. By age 65 about half of all Americans have developed some degree of lens clouding, although it may not impair vision. Other factors that increase your risk of cataracts include:
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