Ophthalmology, branch of medicine concerned with the function and care of the eye and with the disorders that affect it. An ophthalmologist is a physician who has graduated from medical school and completed at least three additional years of special training in the diagnosis and treatment of eye disorders. Ophthalmologists are qualified to perform medical eye examinations, prescribe corrective eyeglasses and contact lenses, treat diseases of the eye, and perform eye surgery. Some ophthalmologists specialize in treating particular parts of the eye, such as the cornea (the transparent cap at the front of the eye) or the retina (the light-sensitive membrane lining the back of the eye). Others specialize in working with specific patient populations. Pediatric ophthalmologists, for example, focus on eye problems of children, such as strabismus, or cross-eye.
An ophthalmic examination can reveal the presence of many disorders, ranging from simple vision problems to infections such as conjunctivitis and trachoma. Eye exams commonly reveal other health problems as well, such as high blood pressure, diabetes mellitus, and brain tumors. During an eye exam, an ophthalmologist uses an ophthalmoscope or other special instrument to view the interior of the eye, particularly the retina. A simple eye chart is often used to help diagnose the most common vision disorders: nearsightedness, farsightedness, and astigmatism. These disorders are caused by an abnormally shaped eye that prevents the cornea and lens from correctly focusing light on the retina, resulting in distorted vision. They are typically treated with glasses or contact lenses. Two forms of laser surgery are sometimes used to reshape the eye's cornea in order to reduce or correct nearsightedness or farsightedness, thereby reducing or eliminating the need for corrective lenses. In photorefractive keratectomy (PRK), an ophthalmologist uses a laser beam; with laser in situ keratomileusis (LASIK), the ophthalmologist uses a laser beam and a tiny blade to reshape the cornea.
Glaucoma, a disorder that causes increased pressure on the optic nerve and can lead to blindness, is one of the more serious common eye diseases in the United States. Ophthalmologists generally check patients for glaucoma in the course of a regular eye exam using a tonometer, a device that measures the pressure of fluids in the eye. The disorder can be treated successfully with drugs if diagnosed in its early stages. Another common eye disorder, found primarily in senior citizens, is macular degeneration, which causes loss of the ability to see at the center of the field of vision due to nerve cell layer damage in the retina. Macular degeneration is generally irreversible, and it usually does not respond to treatment. However, treatments under study, including cellular transplants and use of the drug thalidomide, show promise. Cataract, a clouding of the lens of the eye, is also common in the elderly-the majority of people over age 75 have some degree of clouding. A painless condition, the clouding causes a progressive loss of clarity and detail of images. Cataract is commonly treated with surgery, in which the clouded lens is removed and replaced with an artificial lens.