Regular eye exams best glaucoma preventionby Dick PetersonPublic Relations So you can spot a gnat on a fencepost at 50 yards. You think that’s reason enough to skip eye exams? Having great eyesight can’t prevent blindness. Having regular checkups that include tests for glaucoma can. MUSC ophthalmologist and glaucoma specialist David A. Lee, M.D., calls glaucoma a group of eye diseases that can cause irreversible blindness if undetected or discovered too late. Glaucoma is often associated with increased pressure in the eyeball that inflicts damage on the optic nerve in the back of the eye which can lead to irreversible blindness. Here’s what happens: A clear fluid full of nutrients, called aqueoushumor, is constantly pumped into and drains out of the eye to maintain normal vision. A balance of fluid production and drainage maintains a healthy and normal pressure inside of the eyeball which is important for good vision. When the fluid drainage becomes blocked and results in the pressure increasing in the eyeball, this can damage the main nerve for vision in the back of the eye, called the optic nerve. And it’s the treatment to keep the pressure inside of the eye from going too high and damaging the optic nerve that prompts Lee to laughingly compare himself to an eye plumber. “Usually treatment for glaucoma begins with eye drops,” Lee said. “And there are several different medications that can lower the eye pressure by either slowing the flow of aqueous humor into the eye or increasing the drainage of aqueous humor out of the eye.” One type of laser surgery directed at the blocked drainage system in the eye can make the drainage of aqueous humor out of the eye easier and result in lower eye pressure, but the effects of this laser surgery can diminish over time and some laser surgery patients still need to continue taking glaucoma medications. The treatment of last resort—performed when eye drops, pills or laser surgery fails—seeks to reduce the pressure in the eye by surgically bypassing the blocked drainage system and creating an alternative route to release the aqueous humor from inside of the eyeball. Normal pressure can range between 10 to 21 millimeters of mercury, but glaucoma sufferers can experience pressures as high as 80, Lee said. At first, the pressure change is imperceptible if it is gradually increasing. “Asymptomatic and asymmetrical,” Lee said, explaining that glaucoma can develop in one eye and not the other, or at different rates in both eyes. Gradually diminishing vision in one eye can be covered by the healthy eye compensating for it. The glaucoma sufferer may notice difficulty seeing in dim light or experience a loss of peripheral vision. Sometimes, eye pain, redness, and rapid vision loss can occur when the pressure increases suddenly to very high levels. Acute glaucoma can even be misdiagnosed as a stomach ailment by causing nausea and vomiting from the sudden elevation of pressure inside of the eye to very high levels. While anyone can fall victim to glaucoma especially with increasing age, the disease most commonly strikes individuals over 40 and people with a family history of glaucoma. Blacks are four-to-six times more likely to have glaucoma than whites. Given the usually imperceptible onset of glaucoma, regular eye exams that include a test for glaucoma are the best preventive measure against this treatable cause of blindness. “The tests are simple and painless,” Lee said, “and done by a device that gently touches the surface of the anesthetized eye and measures intraocular pressure. Another device sends a puff of air against the surface of the eye to measure the intraocular pressure.” A microchip implant, a device under development that Lee said could improve glaucoma detection and treatment in high risk patients, would continuously measure variations in intraocular pressure through the day and night. “This intraocular pressure fluctuation can damage the optic nerve,” Lee said. “The intraocular pressure variation in some people can be missed if it is only measured in the doctor’s office during normal working hours.” He said that a normal pressure during an eye exam can change when a person is eating or sleeping at other times during the day or night. Lee said that the Storm Eye Institute and Department of Ophthalmology is continually looking for better diagnosis and treatment methods, including research into ways to repair the optic nerve damaged by glaucoma. “When we teach medicine here,” Lee said, “we don’t teach history. We
are looking for new discoveries in the diagnosis, treatment, and cure for
disease. And this translates into better patient care.”
Friday, Feb. 18, 2005
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