Glaucoma is usually caused when the pressure of the fluid inside the eye increases.

Here’s how that happens: A liquid called intraocular fluid (aqueous humor) is produced inside the eye and fills the cavity behind the eye’s lens. Normally, this drains out through the eye’s drainage system. But when you have glaucoma, the fluid either drains too slowly or stops draining altogether. It’s not clear why this happens. When it does, the intraocular fluid builds up and increases pressure inside the eye (intraocular pressure). This increased intraocular pressure can damage the optic nerve and cause vision loss.

The Most Common Forms of Glaucoma

There are several types of glaucoma. The two most common are:

  1. Open-angle glaucoma. This is the most common type of glaucoma, especially in older adults. It occurs when intraocular fluid drains too slowly, which increases intraocular pressure and, over time, damages the optic nerve. Because damage to the optic nerve occurs slowly and doesn’t cause pain, there are no warning signs. By the time you notice vision problems, you may have significant vision loss. Open-angle glaucoma usually affects your side (peripheral) vision first and can lead to “tunnel vision.” Open-angle glaucoma can also affect your central vision. If untreated, it can ultimately cause blindness. 
  2. Angle-closure glaucoma. In this type of glaucoma, drainage of intraocular fluid is partly or completely blocked. Fluid in the eye builds up, increasing intraocular pressure and damaging the optic nerve. In contrast to open-angle glaucoma, with angle-closure glaucoma intraocular pressure rises rapidly, which can cause severe damage and vision loss. This is a medical emergency and requires immediate treatment to prevent blindness.

How Common is Glaucoma?

Your odds of developing glaucoma increase as you get older. About 1 in 20 adults 65 and older develop glaucoma. Roughly 1 in 10 adults 80 and older develop the disorder.

Risk factors

Your risk of developing glaucoma is higher if you have these factors:

  • Age older than 60. The older you are, the higher your risk.
  • Race and ethnic background. There is a higher risk if you are African-American, Asian, or Hispanic. Glaucoma is the leading cause of blindness in African Americans.
  • Genetics. You have a higher risk if glaucoma “runs in your family.”
  • Pre-existing eye conditions. If you already have poor vision, previous severe eye injury, or other eye problems, you are at higher risk.
  • Other health conditions. Diabetes, high blood pressure, or heart disease puts you at a higher risk.
  • Medication history. You are also at a higher risk if you have used corticosteroid eye drops or ointments, or medications such as prednisone, for long periods of time.


Last Updated August 2020