What is a glaucoma?

Glaucoma is commonly referred to as the silent thief of sight and is one of the leading causes of preventable blindness worldwide. It affects over 3 million Americans and 70 million people around the world, most of whom don’t even know they have it.

Glaucoma is a group of eye diseases characterized by damage to the optic nerve, the nerve that transmits visual information from the eye to the brain. In most cases, this nerve damage is produced by increased fluid pressure within the eye. This elevated pressure is caused by a backup of fluid in the eye. Over time, it causes damage to the optic nerve. Through early detection, diagnosis and treatment, you and your doctor can help to preserve your vision and often protect your eyes against serious vision loss.

Think of your eye as a sink, in which the faucet is always running and the drain is always open. The aqueous humor is constantly circulating through the anterior chamber. It is produced by a tiny gland, called the ciliary body, situated behind the iris. It flows between the iris and the lens and, after nourishing the cornea and lens, flows out through a very tiny spongy tissue, only one-fiftieth of an inch wide, called the trabecular meshwork, which serves as the drain of the eye. The trabecular meshwork is situated in the angle where the iris and cornea meet. When this drain becomes clogged, aqueous cannot leave the eye as fast as it is produced, causing the fluid to back up. But since the eye is a closed compartment, your “sink” doesn’t overflow; instead the backed up fluid causes increased pressure to build up within the eye. We call this open (wide) angle glaucoma.

To understand how this increased pressure affects the eye, also think of your eye as a balloon. When too much air is blown into the balloon, the pressure builds, causing it to pop. But the eye is too strong to pop. Instead, it gives at the weakest point, which is the site in the sclera at which the optic nerve leaves the eye.

The optic nerve is part of the central nervous system and carries visual information from the eye to the brain. This cranial nerve is made up of over one million nerve axons, which are nerve fiber extensions of the retinal ganglion cells. When the eye pressure is increased and/or other inciting factors exist, the optic nerve becomes damaged and the retinal ganglion cells undergo a slow process of cell death termed “apoptosis.” The death of the retinal cells and degeneration of the nerve fibers results in permanent vision loss. Early diagnosis and treatment of glaucoma can help prevent blindness.