What is glaucoma?
Glaucoma is a disease of the optic nerve, which is the part of the eye that carries the images we see to the brain. The optic nerve is made up of many nerve fibers, like an electric cable containing numerous wires. When damage to the optic nerve fibers occurs, blind spots develop. These blind spots usually go undetected until the optic nerve is significantly damaged. If the entire nerve is destroyed, blindness results.
Early detection and treatment by your ophthalmologist are the keys to preventing optic nerve damage and blindness from glaucoma.
What causes glaucoma?
Clear liquid, called the aqueous humor, circulates inside the front portion of the eye. A small amount of this fluid is produced constantly, and an equal amount flows out of the eye through a microscopic drainage system, maintaining a constant level of pressure within the eye. (This liquid is not part of the tears on the outer surface of the eye.)
Because the eye is a closed structure, if the drainage area for the aqueous humor--called the drainage angle--is blocked, the excess fluid cannot flow out of the eye. Fluid pressure within the eye will increase, pushing against the optic nerve and potentially causing damage.
What are the different types of glaucoma?
Chronic open-angle glaucoma: This is the most common form of glaucoma in the United States.
The risk of developing chronic open-angle glaucoma increases with age. The drainage angle of the eye becomes less efficient over time, and pressure within the eye gradually increases, which can damage the optic nerve. In some patients, the optic nerve becomes sensitive to normal eye pressure and is at risk for damage. Treatment is necessary to prevent further vision loss.
Chronic open-angle glaucoma damages vision so gradually and painlessly that you are not aware of trouble until the optic nerve is already injured.
Closed-angle glaucoma: Sometimes the drainage angle of the eye may become completely blocked. In the eye, the iris (the part that makes eyes blue, brown or green) may drop over and completely close off the drainage angle. You can imagine this occurring much like a sheet of paper floating near a drain. If the paper suddenly drops over the opening, the flow is abruptly blocked.
When eye pressure builds up suddenly, an acute closed-angle glaucoma attack occurs. Symptoms may include:
- blurred vision
- severe eye pain
- rainbow-colored halos around lights
- nausea and vomiting
This is a true eye emergency. If you have any of these symptoms, call your ophthalmologist immediately. Unless this type of glaucoma is treated quickly, blindness can result.
In some patients, glaucoma has features of both the chronic open-angle type and the acute closed-angle type. This may be called chronic closed-angle glaucoma or mixed mechanism glaucoma.
Who is at risk for glaucoma?
Your ophthalmologist considers many kinds of information to determine your risk for developing the disease. The most important risk factors include:
- elevated eye pressure
- family history of glaucoma
- African ancestry
- past eye injuries
Your ophthalmologist will weigh all of these factors before deciding whether you should be monitored closely as a glaucoma suspect. This means your risk of developing glaucoma is higher than normal, and you need to have regular examinations to detect the early signs of damage to the optic nerve.
How is glaucoma detected?
Regular eye examinations by your ophthalmologist are the best way to detect glaucoma. A glaucoma screening that checks only the pressure of the eye is not sufficient to determine if you have glaucoma. The only sure way to detect glaucoma is to have a complete eye examination. During your glaucoma evaluation, your ophthalmologist will:
- measure your intraocular pressure
- inspect the drainage angle of your eye
- evaluate whether or not there is any optic nerve damage
- test the peripheral vision of each eye
How is glaucoma treated?
As a rule, damage caused by glaucoma cannot be reversed. Eyedrops, laser surgery and surgery in the operating room are methods used to help prevent further damage. In some cases, oral medications may also be prescribed.
With any type of glaucoma, periodic examinations are very important to prevent vision loss. Because glaucoma can progress without your knowledge, adjustments to your treatment may be necessary from time to time.