Glaucoma is an eye disease caused by increased fluid pressure inside the eye. The disease is the number one cause of irreversible blindness when left untreated. Here, a brief animated video describes why glaucoma develops and how it leads to vision loss.*

Eye Anatomy (0:13)

The front of the eye consists of two chambers.

• The anterior (front) chamber is found between the iris (colored part of the eye) and cornea (clear front surface covering the iris, pupil, and anterior chamber).
• The posterior (rear) chamber is located between the iris and the lens.

There are two main eye structures involved in glaucoma:

• The ciliary body, in the rear chamber, produces a lubricating fluid called aqueous humor that flows from the rear chamber into the front chamber through the pupil.
• The trabecular meshwork, in the front chamber, drains fluid from the eye.

In a healthy eye, fluid is produced and drained at an equal rate, maintaining a normal, constant pressure. 

Why glaucoma develops (0:53)

Glaucoma occurs when this delicate balance between fluid production and drainage is upset. This is usually caused by overproduction of fluid or insufficient drainage, from either disease or injury. When the drainage system becomes blocked, or otherwise goes awry:

• Fluid builds in both chambers, raising pressure inside the eye,
• The increased pressure pushes the lens backward into the vitreous body (the main eye cavity), and 
• Blood vessels and nerve fibers at the back of the eye become compressed and sustain damage. 

Initial damage causes patches of vision loss. If left untreated, total blindness can result.

Open-angle glaucoma (1:21)

Open-angle, or chronic, glaucoma is one of two major types (and the most common form) of the disease.

• Open-angle glaucoma happens when there’s a partial blockage of fluid drainage.
• The angle (space) between the iris and cornea remains open, so the entrance to the drainage canal is unobstructed, but fluid outflow is abnormally slow.
• Pressure rises gradually over a long period, often years.

Symptoms are progressive and may initially go unnoticed.

• Loss of peripheral (side) vision generally occurs first.
• Central vision loss happens over time, if left untreated.

Angle-closure glaucoma (2:05)

Angle-closure, or acute, glaucoma is the second major type of glaucoma.

• Angle-closure glaucoma happens from a sudden and complete drainage block.
• Eye pressure rises rapidly and blindness can happen quickly.
• Eye anatomy issues can make a person susceptible to angle-closure glaucoma.
• It can also happen to anyone with blunt eye trauma.

Monitoring eye pressure (2:29)

When glaucoma is suspected, a tonometer can be used to measure the flexibility of the cornea to external pressure from air or a gently applied device.

• Like a balloon, the cornea will have less flexibility and become more rigid as internal pressure rises.
• Tonometer measurement is routinely performed during eye exams.

Glaucoma progression can be stopped, but any vision loss is permanent. This is why early disease detection is critical through regular eye exams.

*Fauquier ENT. (2022, July 8). Glaucoma (Animation of Why It Happens and How It Can Cause Blindness) [Video file]. Retrieved from https://www.youtube.com/watch?v=hz7MKn3Gwig