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| View through a clear lens |
View through a cataract |
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Photos courtesy of the National Eye Institute, NIH
What is a cataract?
A cataract is an opacification or clouding of the lens of the eye. The lens helps to focus light onto the retina. The light-sensitive cells in the retina then transmit visual signals via the optic nerve to the brain. The perception of a clear, sharp image depends on a clear lens. As we age, however, the lens begins to opacify. The cloudy lens, or cataract, blocks and scatters the light, making it difficult for one to see.
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Who is at risk for cataract?
Cataracts are a normal part of aging. More than half of Americans 65 years or older have cataracts. Cataract formation may be hastened by trauma to the eyes, certain systemic diseases (e.g., diabetes) and medications (e.g., corticosteroids), smoking, and poor nutrition. Exposure to ultraviolet light over one's lifetime has been associated with earlier cataract formation. The use of sunglasses capable of blocking ultraviolet-B (UVB) radiation is a reasonable precaution for outdoor activities.
Diagram courtesy of the National Eye Institute, National Institutes of Health
What are the symptoms?
Cataracts tend to develop slowly, with gradual worsening of vision. Symptoms include:
- Cloudy or blurry vision.
- Colors that seem faded.
- Difficulty driving at night because headlights seem too bright.
- Problems with flare from lamps or the sun.
- Frequent prescription changes in your eyeglasses or contact lens.
- Double or multiple vision.
Other eye diseases besides cataracts may cause these symptoms. See your ophthalmologist or eye care professional if you have any of these symptoms! A regular eye exam is all that is needed to find a cataract if present.
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How is a cataract treated?
For early-stage cataracts, a change in the strength of your prescription (glasses, bifocals, or contact lenses) or the use of a magnifying lens may improve your vision enough to allow you to do the tasks you like to do. Surgery is indicated when you cannot do the things you like or need to do because your vision is too poor even with corrective lenses. Surgery consists of removal of all or part of the cloudy lens. An artificial lens (intraocular lens implant or IOL) is usually used to replace the removed natural lens.
Usually after removing the bulk of the lens, the surgeon leaves behind the back half of the lens capsule, a thin membrane that then functions to hold the intraocular lens implant in place. Use of sound waves (ultrasound) to break up the cataract before removal allows for modern cataract surgery to be performed through a small incision, often less than 3 millimeters in length. Smaller incisions heal more rapidly than larger incisions. This procedure using ultrasonic energy is called phacoemulsification (pronounced FAY-co-ee-mul-sih-fih-CAY-shun).
The success rate of cataract surgery is over 95 percent in patients with otherwise healthy eyes. Patients with coexisting ocular disease (e.g., diabetic retinopathy) may have a greater risk of complications or lack of visual improvement. Modern cataract surgery is one of the most common operations in the United States and is one of the safest and most effective. However, complications can occur, just as they may in any surgery. Be sure to discuss with your surgeon the complications possible so that you can weigh the risks and benefits of cataract surgery when making your decision as to when to proceed.
Diagram courtesy of the Agency for Health Care Policy and Research
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When should a cataract be removed?
Cataract surgery is elective for the vast majority of patients. Surgery should be considered when one cannot perform the activities of daily living because of poor vision due to cataract. Surgery may be beneficial when one:
- Needs to drive, but there is too much glare from the sun or headlights.
- Cannot see well enough to perform one's tasks at work.
- Cannot see well enough to do the tasks one needs to do at home (e.g., cook, clean, repair).
- Cannot see well enough to do the things one likes to do (e.g., read, watch television or movies, sew, play games or sports).
- Is afraid of bumping into objects or falling.
- Is not as independent as one would like because of poor vision.
- Is not improved sufficiently by glasses.
The result of cataract surgery is usually the same whether a person waits for months or years before having the surgery. You have time to carefully consider your options before deciding to proceed.
Rarely there may be instances where your ophthalmologist advises removal of the cataract for medical reasons (e.g., when the cataract is too dense to allow the ophthalmologist to see into the eye to watch over coexisting retinal disease).
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How can I find out more?
If you would like to schedule a consultation with one of the ophthalmic surgeons at the University of Texas Southwestern Medical Center at Dallas, please call 214-645-2020.
For more information about cataracts as well as other common medical problems, visit the Agency for Health Care Policy and Research's web site. The AHCPR is an agency of the U.S. Department of Health and Human Services.
Written by Preston H. Blomquist, M.D., F.A.C.S.
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