A cataract is a cloudy area in the normally clear lens inside the eye. The cloudy area worsens as protein fibers in the lens clump together, preventing light rays from passing through the lens and focusing on the retina, the light-sensitive membrane that lines the back of the eye. Cataracts usually develop very gradually, and early changes in the lens of the eye may go unnoticed. As the cataract continues to develop, symptoms begin to appear. The person may have blurred vision in one eye. Bothersome glare caused by bright sunlight or vehicle headlights is common. The person also may have poor night vision. Colors appear to be less bright. The person may experience increased nearsightedness that requires frequent changes in his or her eyeglass prescription. The person also may find it more difficult to see well enough to read and perform other daily tasks.
Cataracts in adults can be classified into three general types, depending on their location in the lens. The most common type is called a nuclear cataract or an age-related cataract and occurs in the center of the lens. The term "age-related" is somewhat misleading because people can have this type of cataract in their 40s and 50s. During middle age, most cataracts are mild and do not affect vision. After age 60, however, cataracts more commonly begin to interfere with 391
vision. The second type of cataract is a cortical cataract, which starts as a wedge- Eyes shaped spoke at the outer layer of the lens. The spoke descends from the outer layer into the center, where it obstructs the transmission of light. This type of cataract can develop in people who have diabetes. The third type of cataract is called a subcapsular cataract. It starts as a small clouding at the back of the lens and develops slowly.
The exact cause of cataracts is unknown, although doctors have identified certain factors that may be involved in their development. Research has shown that people who live at high altitudes or who spend much time in the sun develop cataracts earlier than other people. Many ophthalmologists now advise people to wear sunglasses that protect against both ultraviolet A and B (UV-A and UV-B) rays and to wear a wide-brimmed hat to protect the eyes against sun exposure whenever they go outdoors. People who have diabetes also seem to have an increased risk of developing cataracts, as do those who take certain medications, such as corticosteroids. If you have any of these risk factors, talk to your doctor about your chances of developing cataracts.
To diagnose cataracts, an ophthalmologist will perform a thorough eye examination. He or she will dilate your pupils with eyedrops and will examine the inside of your eyes with a slit lamp microscope (a viewing instrument with a bright light and magnifying lenses) to detect any clouding of the lens. If a cataract is present, the doctor will determine the type, size, and location of the cataract.
At present there are no eyedrops or other medications that will eliminate cataracts. At first, your vision may be improved with prescription eyeglasses, bifocals, a magnifying glass for reading, or better lighting at home or at work. Once your vision becomes so poor that it affects your ability to function independently, you will probably need to undergo surgery to have the cataracts removed. However, you may not need surgery for many years; some people with cataracts never need surgery.
During cataract surgery the surgeon removes the clouded lens and usually replaces it with an artificial lens. Cataract surgery is one of the most common operations performed in the United States and also is one of the most successful. Good vision is restored in more than 90 percent of people who have cataract surgery. After surgery you will probably have to use eyedrops or wear protective eyeglasses for a time. Your vision may not become fully restored until a few weeks or months after surgery. Most people with a lens implant will need to wear bifocals.
In some cases the posterior capsule (the membrane at the back of the lens) may become cloudy months or even years after cataract surgery, causing blurred vision. This condition can be corrected with a surgical procedure that uses a laser (a highly concentrated, powerful beam of light). The procedure is
Concerns brief and painless and can be performed in the doctor's office or in an outpatient facility.
If you are over age 60, the best way to protect your vision and to check for cataracts is to have your eyes examined by an ophthalmologist at least every 2 years. The examination should include dilation of the pupil so the doctor can see the lens and the back of the eyes. If a cataract is detected, your ophthalmologist will work with you to decide on the best course of treatment and will explain the risks and the benefits of cataract surgery.
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