Prevent Vision Loss - Get Screened for Open-Angle Glaucoma

Glaucoma is one of the leading causes of visual impairment and blindness, affecting as many as 2.2 million people in the United States. Routine eye exams are the best way to detect glaucoma and prevent vision loss, says James C. Robinson, MD, Medical College of Wisconsin Associate Professor of Ophthalmology.

Anatomy of the Eye
The human eye is a complex structure made of many layers that work together to focus light on the retina. The retina is the tissue at the back of the eye that sends visual signals to the optic nerve, which transmits the signals to the brain. In the brain, the signals are processed and transformed into the images we see.

The outermost layer of the eye is the cornea - the clear, dome-shaped surface that covers the front of the eye.

Behind the cornea lies the anterior chamber, a space filled with fluid that nourishes the eye. The fluid drains from the chamber into the angle between the cornea and iris - the colored ring surrounding the pupil - then flows through a network of spongy tissue and out of the eye.

Glaucoma occurs when this fluid drains too slowly or not at all. As the fluid builds up, the pressure inside the eye rises. Over time, this can damage the optic nerve, disrupting the visual signals to the brain.

"There are many, many different kinds of glaucoma," Dr. Robinson says. "They are generally broken down into open-angle and closed-angle types."

Open-Angle Glaucoma Most Common
In open-angle glaucoma, the most common form, the fluid leaves the anterior chamber too slowly, leading to a gradual increase in pressure. At first, open-angle glaucoma usually has no symptoms, Dr. Robinson says.

"In open-angle glaucoma, the pressure gradually creeps up. You can actually lose quite a bit of nerve tissue before it starts to affect your peripheral (side) vision. You're born with about 1.2 million nerve fibers in each optic nerve, and you can lose a significant portion of them before you start to see changes."

As the disease progresses, people with glaucoma can usually see objects in front of them clearly, but objects to the side can be missed.

Without treatment, people with glaucoma will continue to slowly lose their peripheral vision. Their sight will be limited from the edges until they seem to be looking through a tunnel. Over time, straight-ahead vision may decrease to the point where no vision remains.

In closed-angle glaucoma, which is much less common, the eye fluid is blocked and cannot drain, causing a sudden increase in eye pressure. Symptoms include severe pain, nausea, blurry vision and corneal swelling. "It's something that happens very quickly," Dr. Robinson says. Closed-angle glaucoma is a medical emergency.

Other types of glaucoma are associated with conditions such as eye inflammation, eye injury, or advanced cataracts.

Although glaucoma is rare in children, it can occur, and is treated the same as it is with adults - medications initially, and surgery if it becomes necessary. Sometimes childhood glaucoma is a result of a genetic variation. This type of inherited glaucoma is often corrected with surgery.

Screening and Treatment Can Save Vision
Regular eye exams can detect early signs of open-angle glaucoma before patients even notice any vision loss. Then treatment can begin immediately and vision can be preserved. "The sad situations are the patients who come in who've lost a tremendous amount of their side vision and don't even realize it."

"Probably the most important part of the eye exam is the dilated portion and examination of the optic nerve," Dr. Robinson says. To dilate your eyes, the doctor will apply eye drops that cause the pupil to widen; this allows him or her to better see the inner structures of the eye.

Risk Factors
Anyone can develop glaucoma, but certain people are more at risk than others, according to the National Eye Institute. They include:

• African Americans older than age 40
• Everyone over age 60, especially Mexican Americans
• People with a family history of glaucoma

Treatment
Because there are often no signs of open-angle glaucoma, making sure that patients follow a treatment plan can sometimes be a challenge. "Treating eye pressure is much like treating blood pressure," Dr. Robinson said. "You take the pills for your blood pressure; you don't feel any different. You take the drops for your glaucoma; you don't feel any different." Patient education is a key component of treatment.

"People who come in who have had family members who've lost their vision are very good about taking their medications," he notes.

In his practice, Dr. Robinson progresses from non-invasive treatments such as medication to more invasive treatments including laser surgery, which can often help fluid drain from the eye, and traditional surgery, in which the surgeon creates a new opening for fluid to leave the eye.

"The majority of open-angle glaucoma cases can be controlled with medications - whether it takes one, two, three or four, it all depends," Dr. Robinson says. "It depends on the patient's motivation."

Early treatment is vital to protect the eyes and prevent vision loss. "Especially as people get older, they need to have routine eye exams," Dr. Robinson says. "If nothing else, do it for your own peace of mind."

Dr. Robinson practices at the Eye Institute of the Medical College of Wisconsin and Froedtert Hospital and at the Eye Institute - West in Pewaukee, Wisconsin.

-Melissa Rigney Baxter, HealthLink Contributing Writer
-Eileen Early, RN, BSN, HealthLink Editor

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.