Cataract and Seniors
Cataracts are clouding of the lens portion of the eye. The result is much like smearing grease over the lens of a camera and impairs normal vision.
Cataracts will affect most people if they live long enough. This disorder affects 60 percent of people older than 60 and occurs when the normally clear, aspirin-sized lens of the eye starts to become cloudy. impairing vision.
Experts estimate that millions of people are diagnosed annually with cataracts that require treatment. As their is are growing numbers of elderly, the incidence of cataracts is increasing. These persons often want to continue driving cars, reading and traveling-activities for which clear sight is vital.
Until recently, anyone who developed cataracts and needed surgery faced a procedure that involved pain and often less than satisfactory results. Until the late 1970s, doctors removed the cloudy lens in a surgical procedure that required a hospital stay of five to seven days. Afterward, the patient had to wear thick "Coke bottle" glasses or contact lenses neither of which could completely restore vision to its previous level.
Today, there's little need for such complicated treatment. Advances in medicine have made cataracts much less worrisome. Now, the clouded lens is surgically removed and replaced with a plastic intraocular lens (IOL) in an hourlong operation that often requires no hospitalization.
The intraocular lens has revolutionized the treatment of cataracts. Implantation of the lens is one of the most successful operations in medicine.
How does a cataract form?
A cataract forms in the eye's lens. the transparent structure behind the iris (the colored membrane surrounding the pupil). The lens focuses light on the retina, the light-sensitive membrane at the back of the eye which converts light impulses into nerve signals to produce clear visual images. Clouding of the lens, much like smearing grease over the lens of a camera, can develop at any age but most often appears in people older than 42.
Most cataracts are caused by a change in the chemical composition of the lens. In a small percentage of cases, the chemical changes are caused by a hereditary enzyme defect, trauma to the eye., diabetes, or use of certain drugs, such as the steroid prednisone.
Precisely why cataracts occur with age is unknown, but ultraviolet radiation, particularly from the sun, is thought to play a major role in creating, the chemical change in the lens responsible for most cataracts. Experimental evidence suggests that UV radiation can cloud the lens by forming highly reactive chemical fragments called "free radicals." These, in turn. disrupt the delicate structure of the lens. The type of ultraviolet radiation from the sun called UVB-the kind that causes blistering sunburn and skin cancer-is thought to be a major factor because the lens absorbs these rays.
A study showed that those with cataracts had 20 percent more exposure to sunlight in every year of life and also suggested that cataracts can be prevented by avoiding sun exposure between 10 a.m. and 4 p.m., when sunlight is strongest, and by wearing a wide-brimmed hat and sunglasses.
A cataract can develop so slowly that a person may not even know it's there. If the cataract is on the outer edge of the lens, no change in vision may be noticeable. Cloudiness near the center of the lens, however, usually interferes with clear sight.
What are the symptoms of cataracts?
Symptoms of developing cataracts include double or blurred vision, sensitivity to light and glare (such as bright sun or auto headlights), less vivid perception of color, and frequent changes in eye-glass prescriptions. As the cataract grows worse, stronger glasses no longer improve sight, although holding objects nearer to the eye may help reading and close-up work. The pupil, which normally appears black, may undergo noticeable color changes and appear to be yellowish or white.
How are cataracts diagnosed?
Cataracts are typically detected through a medical eye examination. The doctor can see the abnormal lens using a hand-held viewing instrument (ophthalmoscope). The usual test for visual acuity, the letter eye chart, may not, however, reflect the true nature of visual loss. Other tests-which measure glare sensitivity, contrast sensitivity, night vision, color vision, and side or central vision-help nail down the diagnosis.
Because most cataracts associated with aging develop slowly, many patients may not notice their visual loss until it has become severe. Some cataracts remain small and never need treatment, others grow more quickly and progressively larger. Only when a cataract seriously interferes with normal activities is it time to consider surgery, doctors say. People who depend on their eyes for work, play and other activities may want their cataracts removed earlier than those whose needs are less demanding.
What are the treatment options?
During the diagnostic examination, an ophthalmologist will carefully measure the shape, size and general health of the eye to determine whether a lens implant will be effective. In the relatively small number of cases where it won't be, eye-glasses or contact lenses will improve vision after traditional cataract surgery. Glasses, while used for years, have drawbacks. Their extreme thickness makes them unattractive and heavy. Magnification and distortion of the visual image causes objects to appear closer and 25 percent larger than they are. Peripheral vision may be reduced. Contact lenses provide fairly good vision, but many elderly people have trouble inserting, removing and cleaning them.
An implanted IOL is usually the best replacement. Because the implant is placed in or near the original position of the removed natural lens, vision is restored with good peripheral vision and depth perception yet with minimal magnification and distortion.
Some experts estimate that about 88 of every 100 persons receiving IOLs will achieve 20/40 vision or better. (An individual with 20/40 vision can read letters on an eye chart from 20 feet away, while a person with normal 20/20 vision can read the chart from 40 feet away; 20/40 vision is good enough to get a driver's license in most states.) Among those who do not have other eye diseases, about 94 of 100 will achieve 20/40 vision.
IOLs remain permanently in place, require no maintenance or handling, and are neither felt by the patient nor noticed by others. Eyeglasses with thin lenses for near or distant viewing may still be required, but thick glasses are not necessary. A doctor can determine the appropriate implant prescription with an ultrasound device that measures eye length and corneal curvature. These measurements are combined by computer to calculate the lens power required.