Less frequent than chronic open-angle glaucoma, acute narrow-angle glaucoma is caused by a quick rise in eye pressure to extremely high levels (60 mm Hg or more). This happens when the drainage canals inside the eye get blocked completely. It is usually manifested by the sudden onset of intense pain over one eye, associated with very blurred vision. The aim of treatment is to decrease eye pressure as soon as possible, before permanent and severe damage occurs.
The eye doctor can often (though not always) see whether you are at high risk for acute glaucoma during a regular eye exam. If this is the case, preventive laser therapy can be advised. Women, severely farsighted people, and people with cataract have a greater tendency for developing acute glaucoma than do other people. Certain drugs can also cause this type of glaucoma, mainly comprising those used for common cold, diarrhea, depression and Parkinson's Disease. These drugs do not, however, affect eye pressure in persons with chronic open-angle glaucoma.