Glaucoma entails a buildup of fluid pressure in the eye’s anterior chamber, which lies between the cornea and iris. The eye disease affects about one in 25 Americans, usually after the age of 40. About 85 percent of all cases are chronic open-angle glaucoma, in which the outflow of the clear fluid, called aqueous humor, gradually declines. As the pressure within the anterior chamber increases, the tiny blood vessels that nourish the optic nerve become pinched, causing the nerve to slowly wither and die; the eventual result is blindness. This type of glaucoma may start in one eye and then affect the other eye, with no early warning signs. Closed angle, or congestive, glaucoma, which accounts for less than 10 percent of occurrences, comes on rapidly when the iris is so expanded that it blocks the outflow of fluid. Within days, the eye becomes very red, hard, and painful, causing nausea, and severely disturbed vision, including blurring and halos. Such an attack must be treated as a medical emergency, because the high pressure quickly damages the retina and optic nerve, causing permanent blindness. Congenital, or infantile, glaucoma, a rare birth defect, can also result in blindness if it is not treated early. In some unusual cases, glaucoma is secondary to an infection, tumor, injury, or other circumstance that blocks the outflow of aqueous humor.
Other Causes of Vision Disturbances
Many disorders can cause halos, tunnel vision, blurred vision, and other symptoms similar to those of glaucoma; they include a detached retina, macular degeneration, a stroke or mini-stroke, and a tumor of the eye or brain. An eye injury or infection or the presence of a foreign object can also disturb vision.
Diagnostic Studies And Procedures
Because open angle glaucoma generally has no obvious symptoms until it has already damaged the eye, about half of those with the disease do not know they have it. Early diagnosis, essential to prevent vision loss, is possible with a simple procedure called tonometry, in which a probe touches the eyeball to measure pressure in the anterior chamber. Tonometry should be part of a routine eye examination at least every other year after the area of age of35. Although a puff of air may be used to measure eye pressure, this test is not as accurate as the probe. When pressure is abnormally high, further tests are necessary, including an evaluation of peripheral vision. An ophthalmologist diagnoses acute congestive glaucoma on the basis of the sudden onset of symptoms, an eye examination, and tonometry. A doctor may suspect congenital glaucoma when a baby is born with or soon develops an enlarged, protruding eyeball.