A healthy eye has fluid inside it that is always being made and drained. Glaucoma happens when this fluid drains too slowly or does not drain at all. When fluid builds up, pressure inside the eye rises. High pressure can damage the optic nerve. In some cases, doctors are not sure why, but the optic nerve can be damaged even when eye pressure is normal.
The two most common types of glaucoma are:
- Open-angle glaucoma. This is the most common type, especially in older adults. It happens when fluid drains too slowly from the eye. Pressure builds up slowly over time.
- Narrow-angle (also called angle-closure) glaucoma. In this type, the drainage system is partly or completely blocked. Pressure builds up quickly and can damage the optic nerve fast. This is a medical emergency and needs treatment right away to prevent blindness.
Risk factors for Glaucoma
- Age older than 60. Risk goes up as people get older. About 5 percent of people age 65 and older have glaucoma. About 10 percent of people age 80 and older have it.
- Race and ethnic background. People who are Black, Asian, or Hispanic have a higher risk. Glaucoma is the leading cause of blindness in Black Americans.
- Family history. Your risk is higher if glaucoma runs in your family.
- Existing eye problems. People with poor vision, a past serious eye injury, or other eye diseases are at higher risk.
- Other health conditions. Diabetes, high blood pressure, and heart disease can increase risk.
- Medication history. Risk is higher if you use steroid medicines in or around the eye. Some medicines used for congestion, depression, bladder problems, and other conditions can also raise risk.
Last Updated May 2026