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 electrical 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 (Eye M.D.) are the keys to preventing optic nerve damage and blindness from glaucoma.
Glaucoma is the leading cause of blindness I the United States, especially for older people. But loss of sight from glaucoma can often be prevented with early treatment.
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 opt 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 of 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-coloured 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.