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A cataract is a clouding or opaque area over the lens of the eye--an area that is normally transparent. As this thickening occurs, it prevents light rays from passing through the lens and focusing on the retina--the light sensitive tissue lining located in the back of the eye. This clouding is caused when some of the protein which makes up the lens begins to clump together and interferes with vision.
In its early stages, a cataract may not cause a problem. The cloudiness may affect only a small part of the lens. However, the cataract may grow larger over time and affect more of the lens, making it harder to see. As less light reaches the retina, it becomes increasingly harder to see and vision may become dull and blurry. While cataracts cannot spread from one eye to another, many persons develop cataracts in both eyes.
Although scientists do not know for sure what causes cataracts, they suspect there could be several possible causes including:
For several of the potential causes listed (i.e., steroids, diuretics, and/or major tranquilizers), additional research is needed to differentiate the effect of the disease from the effect of the drugs themselves.
The following are the most common symptoms of cataracts. However, each individual may experience symptoms differently. Symptoms may include:
Often in the disease's early stages, you may not notice any changes in your vision. Since cataracts tend to grow slowly, your vision will worsen gradually. Certain cataracts can also cause a temporary improvement in close-up vision, but this is likely to worsen as the cataract grows. The symptoms of cataracts may resemble other eye conditions. Consult a physician for diagnosis.
According to the National Eye Institute, part of the National Institutes of Health, cataract types are subdivided accordingly:
Other sources, including the American Academy of Ophthalmology, describe the different types of cataracts according to the cataract location on the eye lens, including:
In addition to a complete medical history and eye examination, diagnostic procedures for cataracts may include:
In addition, other tests may also be performed to help your eye care professional learn more about the health and structure of your eye.
Possible risk factors for cataracts include:
Specific treatment for cataracts will be determined by your physician based on:
In its early stages, vision loss caused by a cataract may be aided with the use of different eyeglasses, a magnifying glass, or stronger lighting. When these measures are no longer helpful, surgery is the only effective treatment available, for most individuals. It is important to note that a cataract only needs to be removed when vision loss interferes with everyday activities such as driving, reading, or watching television. You and your doctor can make that decision together.
Cataract surgery is one of the most common operations performed and one of the safest and most effective. Surgery involves removing the cloudy lens and replacing it with a substitute lens. If cataracts are present in both eyes, they cannot be removed at the same time. Your physician will need to perform surgery on each eye separately.
Cataracts are generally removed in one of two ways:
According to the National Eye Institute, in most cataract surgeries the removed lens is replaced by an intraocular lens (IOL). An IOL is a clear, artificial lens that requires no care and becomes part of the eye. With an IOL, a person has improved vision because light will be able to pass through the retina. The recipient of the new lens does not see it or feel it.
An "after-cataract" occurs when part of the natural lens not removed during cataract surgery becomes cloudy and blurs vision. Unlike a cataract, an "after-cataract" can be treated with a technique called YAG laser capsulotomy. In an outpatient procedure, the doctor uses a laser beam to make a tiny hole in the lens to let the light pass through.
After-cataracts may develop months, or even years, after cataract surgery.