Millions of Americans take statins, such as Lipitor and Zocor, which are cholesterol-lowering drugs. Along with preventing heart disease, these drugs may have an added benefit of keeping someone from going blind.

A large study confirms anecdotes that statins prevent glaucoma, a common eye condition in people over forty. Yet, about half of those with glaucoma don't know they have it.

Glaucoma develops when pressure slowly increases in the eye from a fluid build-up. Normally, a small amount of fluid is produced and drained daily to nourish parts of the eye that do not have blood vessels and maintain the proper amount of pressure between the various parts of the eye.

But with glaucoma, the fluid does not drain and eeventually the person can't see as well or at all when the optic nerve is damaged. That's the bundle of nerves carrying information from the retina to the brain.

The new study looked at 300,000 who've been on statins for two years to control their cholesterol. They have a nearly 10% lower risk of developing the most common form of glaucoma, open angle glaucoma. Also, the drugs work best in the early stages of the disease.

It is not clear how statins do this. The drugs may improve blood flow to the optic nerve and retinal nerve cells, and help drain the aqueous fluid to reduce pressure in the eye.

People most at risk for glaucoma are African Americans and Hispanics, diabetics, people over sixty, and those with a family history. Once glaucoma robs their sight, it is irreversible. But this can be easily avoided by yearly visits to the ophthalmologist along with a visit to your family doctor.