The exact cause for acute glaucoma is unknown. Normally, clear fluid flows through the front of the eye. Glaucoma occurs when the fluid is unable to drain from the front of the eye. The build-up of fluid causes the pressure to increase inside the eye, which results in damage to the optic nerve and eye pain.

Triggers for acute glaucoma include:

• Medications that cause acute glaucoma
• Exposure to darkness after being in bright light
• Rapid elevations of blood glucose in diabetics