Glaucoma

It is estimated that over two million Americans have some type of glaucoma and half of them do not know it. Glaucoma is a serious disease which may cause blindness, but seldom does when diagnosed and treated early. There are several types of glaucoma, the most common being open-angle glaucoma. The eye receives its nourishment from a clear fluid that circulates inside the eye called aqueous humor. As this fluid is constantly produced, it must also be constantly returned to the blood stream through the eyes drainage canal called the trabecular meshwork. In the case of open-angle glaucoma, something has gone wrong with the drainage canal. When aqueous fluid cannot drain fast enough, pressure inside the eye begins to build. This excess fluid pressure pushes against the delicate optic nerve which connects the eye to the brain. If the pressure remains too high for too long, irreversible vision loss can occur. In the early stages, a person will not experience any symptoms. There is no pain or outside sign of trouble. The early visual changes are very slight and do not affect the central vision, but rather the peripheral vision (the top, sides, and bottom areas of vision) can be lost.

Safe and accurate evaluation for the presence of glaucoma involves several tests. Tonometry is a simple test which measures eye pressure. Ophthalmoscopy is used to visually examine the shape and color of the optic nerve. Perimetry is a test that maps the field of vision, allowing the doctor to see any pattern of visual changes caused by the early stages of glaucoma. Gonioscopy is used to check whether the angle where the iris meets the cornea is open or closed. To control glaucoma, your doctor will use one of three basic types of treatment: medicines, laser surgery, or filtration surgery. A newer type of filtration surgery involves the use of a valve implant to control aqueous drainage from the eye. The goal of treatment is to lower the pressure in the eye.

Glaucoma can occur in people of all races and at any age. The likelihood of developing glaucoma increases if you are African-American, if you have a relative with glaucoma, if you are diabetic, if you are very nearsighted, or if you are over 35 years of age. Even with modern treatments, glaucoma is one of the leading causes of preventable blindness. Everyone should be checked for glaucoma around age 35 and again at age 40. Those considered to be at higher risk, including persons over the age of 60, should have their pressure checked every year or two. With early detection and treatment, vision can be preserved in most cases, and patients are able to lead normal lives.

What is Glaucoma?

Normally, an inflow and outflow of fluid occurs within the eye (green arrows). Note the normal condition of the optic nerve in the back of the eye. Place your cursor over the image to see the cause and effect of glaucoma. When the outflow of this fluid becomes blocked (red arrows), pressure builds up (blue arrows) in the eye. This increased pressure may damage the optic nerve in the back of the eye causing reduced vision.

How Glaucoma Affects Vision

Shown is a normal, full field of vision. When glaucoma is present, (place cursor over image), damage to the nerves of the eye will cause the field of view to be reduced.

The Treatments

Medications - Many types of medications can control glaucoma when used properly.

Laser Trabeculoplasy - Laser can be used to open the "angle" of the eye, to decrease pressure.

Trabeculectomy - Surgical treatments include removal of a small portion of the "angle" area of the eye (red arrow), allowing aqueous drainage (green arrow).

Valve Implant - New developments include placement of a small valve to control the pressure of glaucoma.

Field of view is reduced as glaucoma damages the optic nerve.