A cataract can develop in one or both eyes, and it may or may not affect the entire lens. The lens is located just behind the iris and the pupil. It's shaped like a magnifying glass - thick in the middle and thinner near the edges. Tiny ligaments, which are bands of tough tissue fiber, hold it in place.
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| How To Regain Your Eyesight |
When your eyes work properly, light passes through the cornea and the pupil to the lens. The lens focuses this light, producing clear, sharp images on the retina, the light-sensitive membrane on the back inside wall of your eyeball that functions like the film of a camera. The clouding of the lens, or cataract, scatters the light and prevents a sharply defined image from reaching the retina. Your vision becomes blurred.
The lens consists of three layers. The outer layer is a thin, clear membrane called the capsule. It surrounds a soft, clear material called the 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.
Nuclear
A nuclear cataract is the most common type of cataract and the one most associated with aging. It occurs in the center of the lens. In its early stages, as the lens changes the way it focuses light, you may become more nearsighted or experience a temporary improvement in your 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. As the cataract progresses, the lens may even turn brown. You may have particular problems seeing in dim light and find driving at night especially troublesome.
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 significantly impaired. Focusing problems and distortion are common. You may also have problems with glare and loss of contrast. Many people with diabetes develop cortical cataracts. Cortical cataracts are the only type of cataract associated with exposure to ultraviolet (UV) light.
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 will tend to be more advanced in one eye than the other. A subcapsular cataract often interferes with your reading vision, reduces your vision in bright light and causes glare or halos around lights at night. You're more likely to develop a subcapsular cataract if you have diabetes, are very nearsighted, have taken corticosteroid drugs or have had an eye injury or eye surgery.
Risk factors
Everyone is at risk of developing cataracts simply because age is the single greatest risk factor. And everyone by age 65 has some degree of lens clouding, although it may not impair vision. Cataracts are more common in women than in men, and they're more common in blacks than in whites. Other factors that increase your risk of cataracts include:
- Diabetes
- A family history of cataracts
- Previous eye injury or inflammation
- Previous eye surgery
- Prolonged corticosteroid use
- Excessive consumption of alcohol
- Excessive exposure to sunlight
- Exposure to high levels of radiation, such as from cancer therapy
- Smoking
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| How To Regain Your Eyesight |
The only way to know for sure if you have a cataract is to have an eye examination that includes a visual acuity test, a slit-lamp examination and a retinal exam (ophthalmoscopy). The eye doctor will dilate your pupil to examine the lens for signs of a cataract and, if needed, determine how dense the clouding is. He or she will also check for glaucoma and, if you have blurred vision or discomfort, for other problems with the retina and the optic nerve. If you have a cataract, you can discuss treatment options with your eye doctor.
If in addition to having a cataract you have severe glaucoma or another serious eye condition, removing the cataract may not result in improved vision.To find out more, you can check out How To Regain Your Eyesight.