Most glaucoma is open-angle glaucoma. The disease is a result of pressure inside the eye that is too high for the optic nerve to tolerate, resulting in damage to the nerve which then causes a loss of side or peripheral vision. Unfortunately, there is no pain or other symptoms until after vision loss has occurred. It is a leading cause of blindness, but if caught early it can be controlled. If you are over 40, you should have an eye exam by a doctor of optometry every year or year and a half. If you are African-American, or you have a family member with glaucoma, you are at higher risk for developing glaucoma and should have your eyes examined and eye pressure checked every year.
Narrow-angle glaucoma is much less common and is very different from open-angle glaucoma in that eye pressure usually goes up very fast. There is usually severe pain in the eye or brow ache over the eye, along with redness, swelling, haloes around lights and blurred vision. If not treated promptly, this glaucoma produces blindness in the affected eye in a short period of time.