Healthy Edge
Do you have tunnel vision?
More than 3 million Americans have glaucoma. Only half realize it. A leading cause of blindness in adult Americans, glaucoma isn't called the "sneak thief of sight" for nothing. It damages peripheral vision so gradually that it's unnoticed until "tunnel" vision becomes permanent. If caught early, medical treatment impedes glaucoma's progress. When it comes to glaucoma, early detection is your best friend.
Ever wondered what fills your eyeballs? It's not air. It's compressed fluid partitioned in three chambers - the two front-most chambers have watery fluid, and the one in the rear has a jelly-like substance.
In many glaucoma cases, the pressure in the front-most watery chamber increases, and like dominos, the retina in the rear chamber is affected. Blood flow to the retina is usually reduced as well. The result: nerve cells and fibers associated with your retina are damaged and killed.
Peripheral vision is the first to go. In the most advanced stages, the nerves required for central vision are also damaged - and all sight is lost.
Depending on the type of glaucoma, vision lost can be slow or fast. The two main categories of acquired glaucoma are primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG). POAG is much more common than PACG, and vision loss associated with POAG is typically slow and primarily painless. Conversely, patients who develop acute PACG can lose vision within several hours to days. PACG requires an ophthalmologist's immediate care. Because people know when they have PACG - it's very painful - I'll focus on POAG. Plus, whenever you hear the word "glaucoma" bandied about, the conversation is typically about POAG.
Although what causes glaucoma is generally unknown, multiple factors seem to play a role. The following conditions place you most at risk:
• Over age 80
• A strong family history
• Intraocular pressure (IOP) over 21 mmHg - 10 percent of those with IOPs between 21 and 30 mmHg develop glaucoma
• Moderate to severe myopia - that means you can see nearby objects clearly but not objects in the distance
• African descent
• Migraines
• Low systolic blood pressure - systolic pressure is the top number on your blood pressure reading. It's the pressure exerted when your heart contracts
• Low ocular perfusion pressure - this can result from conditions such as low blood pressure or severe obstructive sleep apnea syndrome
• In women, type 2 diabetes mellitus
• Ocular corticosteroid use
Early diagnosis and treatment can minimize or prevent optic nerve damage and limit glaucoma-related vision loss. The Glaucoma Research Foundation suggests that all individuals, whether they exhibit the above-risk factors or not, should be tested for glaucoma between ages 35 and 40, every two to four years between ages 40 and 60, and every one to two years after age 60.
According to the American Academy of Ophthalmology, effective glaucoma screening goes beyond simply measuring intraocular pressure. It recommends that intraocular pressure measurements be combined with an evaluation of optic nerve status and visual acuity. In isolation, these tests fail to identify a significant number of those people with glaucoma.
For example, although glaucoma risk increases as IOP measurements rise - 11 percent for every 1 mmHg of higher IOP - population-based studies have shown that up to 50 percent of those with glaucoma have IOP levels consistently below 22 mmHg. In other words, half of all glaucoma suffers have IOP levels that are pretty normal.
Currently, lowering IOP is the only means to prevent optic nerve damage and glaucomatous vision loss - even in patients with normal-pressure glaucoma. Typically, your ophthalmologist will initially prescribe eye drops or pills that lower IOP. In some cases, IOP is lowered using surgical techniques such as laser trabeculoplasty (increases outflow) or filtering surgery (creates a bypass for the "watery" fluid). If your laser surgery outcome is poor, your ophthalmologist can still use procedures that reduce the rate of fluid production.
Sadly, avoiding dietary fat, cholesterol and caffeine does not decrease glaucoma risk. More bad news ... although alcohol consumption reduces IOP, it does not affect glaucoma development. And, don't think that antioxidant supplements will help you - they won't.
As I mentioned in the opening, early detection, through regular and complete eye exams, is the key to protecting vision from damage caused by glaucoma.
For more information about glaucoma, visit the Glaucoma Research Foundation at www.glaucoma.org/index.php or call them toll-free at 1-800-826-6693.
