Glaucoma is a group of diseases affecting the optic nerve in one or both eyes. It involves internal eye (intraocular) pressure that is too high for the health of the patient’s eye. Glaucoma can impair vision or lead to blindness, but early detection and treatment can usually prevent serious damage.

Each optic nerve contains about 1.2 million nerve fibers in a cable-like structure that connects the retina to the brain. When the nerve fibers are damaged, the nerve impulses to the brain are thwarted and blind spots develop. Peripheral (side) vision can be reduced so that a person experiences tunnel vision. If untreated, the disease destroys the optic nerve and blindness results.

There is a space in the front of the eye called the anterior (front) chamber. It is filled with aqueous humor, a clear liquid containing nutrients. This fluid needs to flow freely in and out of the chamber to nourish the surrounding tissues. There is an angle where the cornea (clear tissue over the front of the eye) and iris (colored part of the eye around the pupil) meet. Here the fluid drains through a spongy drain called the trabecular meshwork and leaves the eye. If the fluid passes through too slowly, pressure builds. This pressure against the blood flow to optic nerve is believed to damage the nerve and destroy vision.

Having increased eye pressure does not mean someone has glaucoma but does increase the risk of developing the disease. Some individuals tolerate above-normal eye pressure. Conversely, some people with relatively low eye pressure develop glaucoma. This is called low-tension or normal-tension glaucoma.

A recent study known as the OHTS (Ocular Hypertension Treatment Study), showed that early treatment of patients who have high eye pressure reduces the risk of vision loss. The study also showed that patients with thinner corneas have higher pressures than those measured in the ophthalmologist’s office, and may constitute a large portion of the patients with normal-tension glaucoma. These findings have made corneal pachymetry (measurement of the thickness of the cornea) a routine part of a glaucoma examination.

The most common type of glaucoma, open-angle glaucoma, develops gradually and is largely symptomless. The patient will not notice any change in vision until the end stage of the disease when most vision is gone. Early detection of glaucoma is therefore crucial to preventing damage to the optic nerve and preserving vision. Regular eye examinations are necessary, especially for those with risk factors, including people over age 60, people with diabetes or high blood pressure, people with a family history of glaucoma, blacks and Hispanics.

Glaucoma is a major cause of vision loss and blindness in the United States and worldwide. Researchers have projected that the global number of glaucoma cases could hit 60 million by 2010 and 80 million by 2020. If glaucoma is detected and treated early, vision can often be saved. But lifetime monitoring and treatments are required.