American Medical Association Family Medical Guide - American Medical Association [735]
Uveitis is rare, and the cause is usually unknown. However, in some cases, the disorder may result from an autoimmune disorder (in which the immune system mistakenly attacks body tissues) or from infection with a virus such as the herpes simplex virus or herpes zoster virus. Uveitis can occur at any age, but it occurs most frequently in young adults. The disorder can affect one or both eyes.
Because untreated uveitis can lead to serious complications—such as cataracts (see next page); glaucoma (see page 1042); the growth of new, abnormally fragile blood vessels on the retina; or blindness—early detection and treatment are crucial.
Symptoms and Diagnosis
The symptoms of uveitis include eye discomfort, pain, or redness; increased sensitivity to light; and blurred vision. The symptoms may be mild or severe. A diagnosis of uveitis is based on the symptoms and an eye examination.
Treatment
To treat uveitis, a doctor usually prescribes a corticosteroid drug in the form of eyedrops, an ointment, an injection, or a pill to relieve the pain and inflammation. Doctors may also prescribe eyedrops that dilate the pupil to prevent the back of the inflamed iris from sticking to the front of the lens, which could block the flow of fluid out of the eyeball, increasing pressure inside the eyeball. Even with effective treatment, the condition may recur.
Disorders of the Inner Eye
The lens is a transparent, elastic structure inside the eye that enables the eye to focus. It is directly behind the iris (the colored part of the eye) and is attached to a circular muscular ring called the ciliary body. When you look at an object, the ciliary body contracts, changing the shape of the lens and increasing the focusing power of the eye.
The membrane that lines the inside of the back of the eye is called the retina. The retina is covered with nerve cells—called rods and cones—that are specially adapted to detecting light. The cones, which detect fine detail and color, are located more densely in the macula, an area in the center of the retina at the very back of the inside of the eyeball. For this reason, you have to look straight at an object to see it clearly. The rods, which are sensitive to the intensity of the light entering the eye, are located throughout the retina.
When light passes through the cornea, pupil, and lens at the front of the eye, the light rays focus on the retina, which transforms them into nerve impulses. The impulses then pass along the optic nerve at the back of the eye to the areas of the brain that control vision, where they are perceived as images.
Cataracts
A cataract is clouding of the lens of the eye (see page 127). As protein fibers in the lens clump together, the clouding worsens and prevents some light rays from passing through the lens and reaching the retina, the light-sensitive membrane that lines the inside of the back of the eye. Because cataracts usually develop very slowly, early vision changes may not be noticeable. However, as the cataract grows denser, the person’s vision gradually worsens. Cataracts usually do not cause pain.
There are several different types of cataracts. Congenital cataracts are present from birth, or cataracts may develop during childhood. In adults, the most common type of cataract is an age-related cataract, which can begin to develop when a person is in his or her 40s or 50s. Most cataracts are age-related. Another type of cataract is a secondary cataract, which usually develops in people with a chronic disease, especially diabetes (see page 889). A traumatic cataract is a cataract that develops as a result of an eye injury.
Q & A
Cataracts
Q. My grandmother was an independent woman until she developed cataracts. After her vision became impaired, it seemed as though she needed help with just about everything. I am worried that the same thing might happen to me. Is there anything I can do to prevent cataracts?
A. There’s no surefire way to prevent cataracts, but you can