One of the most serious concerns about glaucoma is that it usually has no symptoms or signs in its early stages. As many as half of glaucoma sufferers in the U.S. have the disease and don’t know it, according to the National Eye Institute. Because of the lack of symptoms, regular eye examinations and glaucoma-screening programs are important to the early detection and successful treatment of glaucoma.

In the later stages of the disease, some of the following symptoms may be present:

• loss of peripheral (side) vision,
• headache,
• blurred vision,
• difficulty or inability to adjust vision in darkened rooms,
• difficulty focusing on close work,
• rainbow-colored rings or halos around lights, and
• frequent need to change eyeglass prescriptions.

By the time any of these symptoms occur, however, the eye has already been severely and irreversibly damaged, and the glaucoma may be harder to control. That is why glaucoma is sometimes called “the thief in the night”, because it robs your vision without any signs or symptoms. For that reason, periodic eye exams including glaucoma testing are very important for everyone, even people who seem to have perfect vision.