Open-angle glaucoma is the most common type of glaucoma, in which slow damage to the optic nerve in the back of the eye causes gradual loss of vision. The cause is not well understood but in some cases may be increased pressure in the eye (intraocular pressure) that results from the buildup of fluid inside the eye.

Open-angle glaucoma usually occurs in both eyes at about the same time. However, one eye may be more severely affected than the other eye. At first, the person loses eyesight in the sides or outer parts of vision (peripheral vision) and night vision. Sometimes much of the person's eyesight may be affected before the glaucoma is detected.

If open-angle glaucoma is not treated, the person will continue to lose vision until total blindness develops. Treatment for open-angle glaucoma may require medication (eyedrops) that lowers the pressure inside the eye, laser treatment, or (rarely) surgery.