Glaucoma is a condition in which the pressure of fluid inside the eyes (intraocular pressure, or IOP) slowly rises. This is because the fluid called aqueous humor, which normally flows in and out of the eye, is not draining properly. Instead, it collects inside the eye. This causes pressure damage to the optic nerve (a bundle of more than 1 million nerve fibers that connects the retina with the brain). The damage results in loss of vision.
What causes glaucoma?
While doctors used to think high intraocular pressure (also known as ocular hypertension) was the main cause of optic nerve damage in glaucoma, we now know that even people with normal IOP can lose vision from glaucoma. The exact cause is still unknown.
What are the different types of glaucoma?
With this most common type of glaucoma, the fluid that normally flows through the eye cannot drain, causing a buildup of pressure in the eye. Nearly 3 million Americans are affected each year. Half of these people do not know they have glaucoma.
Low-tension or normal-tension glaucoma
While normal eye pressure ranges between 12 to 21 mm Hg, it is possible to have glaucoma even if pressure is within this range. This type of glaucoma causes optic nerve damage and narrowed side vision.
In angle-closure glaucoma, the angle where fluid normally drains from the eye becomes blocked by part of the iris. This causes a sudden increase in eye pressure. It is a medical emergency, requiring immediate treatment to improve the flow.
Childhood glaucoma is a rare form of glaucoma that often develops in infancy, early childhood or adolescence. Prompt medical treatment is required to prevent blindness.
Congenital glaucoma, a type of childhood glaucoma, occurs in children born with defects in the angle of the eye that slows the normal drainage of fluid. Prompt medical treatment is required.
Both open-angle and angle-closure glaucoma can be classified as primary or secondary. Primary glaucoma cannot be attributed to any known cause or risk factor.
Secondary glaucoma develops as a complication of another medical condition or injury. In rare cases, secondary glaucoma is a complication following another type of eye surgery.
What are the symptoms of glaucoma?
Most people who have glaucoma do not notice any symptoms until they begin to lose some vision. As optic nerve fibers are damaged by glaucoma, small blind spots may begin to develop, usually in the side or peripheral vision. Many people do not notice the blind spots until significant optic nerve damage has already occurred. If the entire nerve is destroyed, blindness results.
One type of glaucoma, acute angle-closure glaucoma, does produce noticeable symptoms because there is a rapid build-up of pressure in the eye. While each person may experience symptoms differently, they may include:
- Blurred or narrowed field of vision
- Severe pain in the eye(s)
- Haloes (which may appear as rainbows) around lights
The symptoms of acute angle-closure glaucoma may resemble other eye conditions. If you notice symptoms, consult a doctor immediately. This type of glaucoma is a medical emergency and requires prompt medical attention to prevent blindness.
How is glaucoma diagnosed?
In addition to a complete medical history and eye examination, your doctor may do the following tests to diagnose glaucoma:
Visual Acuity Test
The common eye chart test (see right), which measures vision ability at various distances.
The pupil is widened with eye drops to allow a close-up examination of the eye's retina.
A test to measure a person's side (peripheral) vision. Lost peripheral vision may be an indication of glaucoma.
A standard test to determine the fluid pressure inside the eye.
What are the risk factors for glaucoma?
Although anyone can develop glaucoma, some people are at higher risk than others. The following are possible risk factors for glaucoma:
African Americans are five times more likely to develop glaucoma than whites. In addition, glaucoma is four times more likely to cause blindness in African Americans than in whites, and 15 times more likely in the age group 45 to 64.
People older than 60 are more at risk for developing glaucoma.
People with a family history of glaucoma are more likely to develop the disease.
High Intraocular Pressure
Persons with an elevated (greater than 21 mm Hg) intraocular pressure (IOP) are at an increased risk. The National Eye Institute, part of the U.S. National Institutes of Health, recommends that anyone in these risk groups receive an eye examination with dilated pupils every two years.
Treatment for Glaucoma
Specific treatment for glaucoma will be determined by your doctor based on:
- Your age, overall health, and medical history
- Extent of the disease
- Your tolerance for specific medications, procedures or therapies
- Expectations for the course of the disease
- Your opinion or preference
While glaucoma cannot be cured, early treatment can often control it. Treatment may include:
Some medications cause the eye to produce less fluid. Others lower pressure by helping fluid drain from the eye.
The purpose of conventional surgery is to create a new opening for fluid to leave the eye.
Laser Surgery (also called Laser Trabeculoplasty)
There are several types of laser surgery used to treat glaucoma, including:
In this, the most common type of laser surgery to treat open-angle glaucoma, a laser is used to place "spot welds" in the drainage area of the eye (known as the trabecular meshwork). This allows fluid to drain more freely.
In this procedure, the surgeon uses the laser to make a small hole in the iris, the colored part of the eye, to allow fluid to flow more freely in the eye.
A procedure that uses a laser beam to freeze selected areas of the ciliary body, the part of the eye that produces aqueous humor, to reduce the production of fluid.
In some cases, one surgical procedure is not effective in stopping glaucoma, and repeat surgery or continued treatment with medications may be necessary.