What is glaucoma?
Glaucoma is an eye disease that is a leading cause of blindness in the United States and the number one cause of blindness in African Americans. Although early treatment can substantially reduce the likelihood of severe vision loss or blindness, many people at higher risk for blindness from glaucoma are unaware of the importance of early detection or are not having their eyes examined on a regular basis for the disease. Increased public awareness of the benefits of a comprehensive eye examination is crucial to help prevent vision loss from glaucoma.
How does open-angle glaucoma affect the eye?
In a healthy eye, aqueous humor (a clear, nutrient-rich fluid) passes continuously through the pupil and into a small space at the front of the eye, called the anterior chamber. As it leaves this area, the aqueous humor flows to the periphery of the chamber, or angle, where it exits through a complex channel system and drains into blood vessels in and near the sclera, the white outer coat of the eye.
In an eye with open-angle glaucoma, the aqueous humor drains too slowly through the channel system, creating a chronic rise in fluid pressure inside the eye. This elevated pressure may gradually interrupt the metabolic processes of cells in the optic nerve, leading to progressive destruction of nerve fibers that are essential for vision. Open-angle glaucoma is so called because the angle of the anterior chamber is open to aqueous humor outflow. It is the slow drainage of aqueous humor through the drainage system that increases fluid pressure.
Conversely, in angle-closure glaucoma, part of the iris suddenly obstructs the angle and blocks the aqueous humor from reaching the drainage system. This causes a very painful rise in intraocular pressure and requires emergency medical attention.
How many Americans have open-angle glaucoma?
Approximately 3 million Americans have open-angle glaucoma, but about half are unaware of it. Glaucoma accounts for over 4.5 million visits to physicians each year.
What is the cost of blindness from open-angle glaucoma?
It is estimated that as many as 120,000 Americans are now blind from the disease. Based on this estimate, blindness due to open-angle glaucoma costs the U.S. government over $1.5 billion annually in Social Security benefits, lost income tax revenues, and health care expenditures.
Who is at risk?
Although open-angle glaucoma can affect anyone, it is most prevalent in African-Americans over age 40 and anyone over age 60. As people grow older, age-related changes in the eyes make them more susceptible to open-angle glaucoma. African Americans are three to four times more likely to develop open-angle glaucoma than Caucasians.
Open-angle glaucoma develops earlier in African Americans (around age 40) than in Caucasians and progresses more rapidly. By age 70, the disease has attacked one in eight African Americans, among whom it is a leading cause of blindness. African Americans are about six times more likely to become blind from the disease than Caucasians.
What are the symptoms of the disease?
At its onset, open-angle glaucoma usually has no symptoms. There is no pain, no blurring of vision, and no ocular inflammation to alert people that they have the disease. But as open-angle glaucoma progresses, it will slowly and insidiously begin to destroy peripheral vision. It is at this point that most people seek treatment, but tragically, vision that has already been lost from glaucoma cannot be restored.
How is glaucoma detected?
The most reliable way to detect open-angle glaucoma is through a comprehensive eye examination with dilated pupils which, when indicated, includes a visual field test. To dilate, or enlarge, the pupils, the eye care professional places medicated drops into the eye. By so doing, the practitioner can better examine the back of the eye for early signs of disease, such as optic nerve damage, before noticeable vision loss occurs. Tonometry is a common and painless test to measure intraocular pressure. In this test, an eye care professional uses an instrument called a tonometer to measure the fluid pressure in the anterior chamber. However, because the elevated fluid pressure is only one characteristic of open-angle glaucoma, tonometry does not always indicate whether or not a person has the disease. Many people with elevated fluid pressure never develop any form of glaucoma, while people with seemingly normal pressure during an examination will develop the disease.
For this reason, tonometry should be viewed as a critical component of the overall examination for glaucoma, but should not be the only test used to detect glaucoma. Testing for glaucoma includes visual field evaluation along with photographs and computerized imaging of the optic nerve. Visual field testing is particularly important because it can detect a patient's early loss of peripheral vision, a sign of open-angle glaucoma.
How is glaucoma treated?
Glaucoma treatment is aimed at controlling the eye's fluid pressure as a means of slowing disease progression. Your doctor will review with you your treatment options which can include laser treatments and or eye drops. Open-angle glaucoma treatments include:
Several medications are available as eye drops to either enhance fluid drainage or decrease the eyes production of aqueous humor are available. All medication has potential side effects, and when they do occur, patients should consult with their ophthalmologist.
Glaucoma treatment using the laser, called Selective Laser Trabeculoplasty (SLT), has shown to lower the pressure in the eye and can sometimes be used as glaucoma treatment ”. In this form of treatment, the laser is directed onto the trabecular meshwork (part of the anterior chamber drainage system) which allows for better fluid drainage.
Several procedures may be performed to improve drainage flow, such as trabeculectomy. Glaucoma surgical procedures involve making a small hole in the anterior chamber through which fluid can leave the eye. Although these procedures have a fairly high success rate, they are generally reserved until medical therapy is no longer effective.