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Q: Would you please give some information about glaucoma? I am using medicated drops to treat my glaucoma. What about surgery?

-- L.K., Munster, Ind.

A: Glaucoma is defined as the progressive loss of vision due to damage to the eye's main nerve (optic nerve). Although it's almost always caused by an increase in the fluid pressure within the eye, some people will develop glaucoma even when the pressure is within the normal range.

Typically, glaucoma occurs when fluid made inside of the eyeball is unable to escape. This causes pressure to build up, which squeezes the eye's main nerve in the back of the eyeball, which can cause blindness.

There are two main ways that fluid is blocked from escaping. The first (and the most common) is when the filter in the drainage tube gets plugged up. This is called open angle glaucoma. Less commonly, the drainage tube may be completely blocked by the part of the eye called the iris. This is called closed angle glaucoma.

About 2 percent of people over the age of 65 have glaucoma. The rate is three times higher in African Americans. One in 10 African Americans over the age of 80 has glaucoma.

Although the genetic link is not known, a person has a higher risk of getting glaucoma if a family member has it. Other factors known to increase risk are being African-American, having diabetes and being very nearsighted.

The best way to deal with glaucoma is to detect it as early as possible by measuring the pressure inside the eyeball. This is often done by blowing a jet of air against the eyeball and seeing how much the eye indents.

But eyeball pressure can be deceptive. As I mentioned earlier, some people will develop glaucoma with what appears to be normal pressure.

Also, eyeball pressure varies quite a bit throughout the day. The pressure tends to be higher in the morning. To be most cautious, the morning is the best time to screen for glaucoma. If a person has symptoms and signs of glaucoma but the pressure is not raised, measuring at different times of the day, especially in the morning, may yield different readings.

A recent medical study showed that if people were treated with medications at the earliest signs of glaucoma, fewer would develop visual problems. And those who did develop problems did so later. Unfortunately the effect of early treatment was limited -- 60 percent of those without treatment got worse, and 45 percent of those who were treated early had more symptoms.

The first line of treatment is medicated eye drops. These work by either reducing the amount of fluid produced or by opening up the drainage. There are five different classes of drugs. Unfortunately, they have not been compared, so it is unknown which one(s) work best for the average person, much less for an individual.

Surgery can be very effective, but it carries a significant risk of causing visual problems. Although laser surgery may have fewer side effects, it is not as effective for all types of glaucoma.

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