What Is Glaucoma?

Glaucoma is an eye disease that can cause blindness. If caught early, it can usually be controlled. But it often has no symptoms, so you need regular eye exams. Glaucoma usually begins when pressure builds up in the eye. This pressure can damage the optic nerve. The optic nerve sends messages to the brain so you can see. There are two main kinds of glaucoma: open-angle and closed-angle.

Side view of eye with arrows inside showing pressure building up. Optic nerve at back of eye is damaged. Closeup of cross section of eye where cornea covers iris. Pupil is opening in center of iris. Lens is behind iris. Fluid drains from behind iris through pupil to front of iris. Fluid then drains out of eye through holes near cornea. Drainage holes may become clogged.

Drainage area

The eye is always producing fluid. The eye's drainage areas may become clogged or blocked. Too much fluid stays in the eye. This increases eye pressure.

Optic nerve

Too much pressure in the eye can damage the optic nerve. If damaged, this nerve cannot send the messages to the brain that let you see.

Open-angle glaucoma

Open-angle is the most common kind of glaucoma. It happens slowly as people age. The drainage area in the eye becomes clogged. Not enough fluid drains from the eye, so pressure slowly builds up. This causes gradual loss of side (peripheral) vision. You may not even notice changes until much of your vision is lost.

Closed-angle glaucoma

Closed-angle glaucoma is less common than open-angle. It usually comes on quickly. The drainage area in the eye suddenly becomes completely blocked. Eye pressure builds rapidly. You may notice blurred vision and rainbow halos around lights. You may also have headaches, nausea, vomiting, and severe pain. If not treated right away, blindness can happen quickly.