MSD Manual

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The Manual's Editorial Staff

Reviewed/Revised Mar 2023
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Topic Resources

What is glaucoma?

Glaucoma is an eye disease that causes vision loss. It usually happens when pressure from extra fluid within your eyeball damages the nerve in your eye (optic nerve).

  • Vision loss usually happens slowly, so you may not notice it right away

  • Glaucoma gets worse over time

  • It can cause lasting vision loss and blindness if not treated

  • Special eye drops (prescribed by your doctor) can lower the pressure in your eye

  • Get a full eye exam every 1 to 2 years to detect glaucoma early and help prevent vision loss

  • If you have glaucoma, the doctor will need to check the pressure in your eyes often


What causes glaucoma?

Glaucoma happens if fluid builds up in your eye, which increases the pressure within your eye.

A healthy eye is full of fluid. The fluid helps it keep the proper shape. Fluid is always being made and then draining out. When functioning properly, the system works like a faucet and a drain in a sink. Balance between fluid production and drainage—between an open faucet and a properly draining sink—keeps the fluid flowing freely and prevents pressure in the eye from building up.

In glaucoma, fluid builds up because something blocks the normal fluid drainage path.

  • In many people, the cause of fluid build-up is unknown

  • In some people, fluid drainage is blocked by another eye problem, such as an infection or a tumor

You can get glaucoma at any age, but it is much more common as you get older.

People at highest risk for glaucoma may have:

What are the symptoms of glaucoma?

Symptoms usually happen slowly over months or years:

  • Blind spots (patches of areas you can’t see) in one or both eyes

  • Blind spots usually on the sides first, then the middle

  • Sometimes eye redness or discomfort, blurry vision, or headache

Vision loss occurs so slowly that you may not notice until much of your sight is lost.

Sometimes symptoms happen suddenly. A sudden attack of glaucoma can be a medical emergency. You may have:

  • Severe eye pain and headache

  • Sudden eye redness, blurry vision, and vision loss

  • Feeling like you want to throw up

  • Seeing rainbow-colored circles around lights

How can doctors tell if I have glaucoma?

Doctors will give you a full eye exam. They will test the pressure in your eye, test for blind spots, and look inside your eye to check your optic nerve for signs of damage.

How do doctors treat glaucoma?

Your doctor will give you medicines (usually eye drops) to lower the pressure in your eye. Sometimes your doctor will recommend surgery.

You can't get back vision that you've lost, but you can prevent further vision loss if you control the pressure in your eyes. You will need to treat your glaucoma every day for the rest of your life, usually even if you've had surgery.

The pressure in your eyes will need to be checked often by an eye doctor to make sure it stays at a good level. If not, your doctor may need to switch the kind of medicine you use.

How can I prevent vision loss from glaucoma?

If you're at risk for glaucoma, get a full eye exam every 1 to 2 years. That way, if your doctor finds glaucoma, you can start treatment to lower the pressure in your eyes, even if you don’t have symptoms yet. Daily treatment will be needed to prevent vision loss.

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