Aging seems to rob us many things�youthful appearance, muscle mass, and perfect eyesight. But there are certain measures we can take to maintain healthy eyes, especially once we�re past age 35, including periodic eye checkups by an ophthalmologist for glaucoma.

Glaucoma is the second-leading cause of blindness in America and has no early warning signs. In fact, a quarter million Americans or more may currently have glaucoma and not even know it. Glaucoma is the number one cause of blindness in African-Americans and the second-leading cause in the general population, according to the American Academy of Ophthalmology. Chronic glaucoma�which accounts for most glaucoma cases�often goes undetected for years, resulting in significant and permanent damage to the eyes. Once you�ve lost your eyesight to glaucoma, it never comes back.

In glaucoma, the peripheral vision is gradually lost. The process can be so gradual that it goes unnoticed by the person affected. Central vision�the ability to see straight ahead�to recognize objects and to read�remains essentially normal until the last stages of the disease.

What can you do to prevent glaucoma? Prompt diagnosis and treatment can prevent blindness and severe vision loss. Even if you have no visual symptoms, you should have periodic eye checkups. A simple 10-minute test called tonometry allows your physician to determine the pressure within your eye. A dilated pupil exam also is very important because it gives your physician a clear view of the interior of your eye and allows him or her to see if there is any damage to the optic nerve. This nerve, which transmits sight, is the nerve damaged by advancing glaucoma. Drug treatment usually helps lower the pressure caused by glaucoma and surgery, if needed, can open a blocked channel or create an artificial one.

Exactly what happens in glaucoma?

The vision loss from glaucoma results from the pressure of the built-up fluid within the eye. Fluid normally passes through a space between the colored portion of your eye (iris) and the transparent membrane structure behind it (lens) and drains out of the eye through a channel that leads to a system of small veins outside the eye. If this outward flow is blocked, pressure can damage the optic nerve�the nerve that transmits vision�and thus reduces your ability to see. Although the reasons are unknown, African-Americans seem be at greater risk for developing glaucoma perhaps because they have a greater susceptibility to high fluid pressure inside the eye. Another group who should be checked more frequently include people age 65 or older.