Glaucoma is a group of eye diseases which result in damage to the optic nerve and vision loss.
For eye pressures a value of greater than 21 mmHg or 2.8 k Pa is often used with higher pressures leading to a greater risk. However, some may have high eye pressure for years and never develop damage. Conversely, optic nerve damage may occur with normal pressure, known as normal-tension glaucoma. The mechanism of open-angle glaucoma is believed to be slow exit of aqueous humor through the trabecular meshwork while in closed-angle glaucoma the iris blocks the trabecular meshwork.
Diagnosis — is by a dilated eye examination. Often the optic nerve shows an abnormal amount of cupping.