What is Glaucoma?

Glaucoma is a leading cause of blindness in North America, especially for older people. Loss of sight from glaucoma is often preventable if you get treatment early enough.

Glaucoma is a disease of the optic nerve. The optic nerve carries the images
we see to the brain. Many people know that glaucoma has something to do
with pressure inside the eye. The higher the pressure inside the eye, the greater the chance of damage to the optic nerve.

The optic nerve is made up of a large number of nerve fibers, like an electric cable containing many wires. Glaucoma can damage nerve fibers, causing blind spots to develop.

Usually people don't notice these blind areas until a large amount of optic nerve damage has already occurred. 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 eye. This fluid must maintain a certain pressure within the eye in order to keep it inflated. That pressure must be less than the pressure of blood flowing into the eye, in order to continue to allow the blood to flow inward.

A small amount of this fluid is produced constantly, and an equal amount flows out of the eye through a microscopic drainage system (left) . (This liquid is not part of the tears on the outer surface of the eye.) If the drainage angle of the eye is blocked, excess fluid cannot flow out of the eye (right).

You can think of the flow of aqueous fluid as working much like a sink with both the faucet turned on and the drain open all the time. If the flow of the fluid stays the same and the drain becomes partly blocked the pressure in the eye will go up just like the water level in a sink with a partially closed drain will rise and the sink may eventually overflow. Because the eye is a closed structure, the excess fluid in the eye cannot overflow if the drain is clogged. If the drainage area of the eye called the drainage angle is blocked, the fluid pressure within the inner eye may increase. Increased pressure can cut off the blood flow into the eye which may result in damage to the optic nerve.