Many people are familiar with the association between elevated eye (intraocular) pressure and glaucoma. While elevated pressure is the principal risk factor for developing glaucoma, there are a number of people who develop glaucoma who have never had pressures above the normal range (10-21). Glaucoma affects nearly three million Americans and it is estimated that at approximately 20-40 percent of these patients have a condition known as “Normal Tension Glaucoma (NTG).”

Like virtually all other glaucomas, NTG causes painless, yet slow damage to the optic nerve, which is the major nerve that sends vision from your eyes to your brain. Most often, the peripheral vision is lost first, and with further damage, the central part of your eyesight is lost. Many people are unaware of any vision problems until the later stages of the condition.

Although NTG affects a good percentage of glaucoma patients, the cause is not completely understood. Despite having pressures in the normal range, a given pressure level may still be too high for the optic nerve fibers to withstand. Some glaucoma experts believe that people with NTG have abnormal optic nerve structure, or perhaps reduced blood supply due to atherosclerosis, fatty deposits within the optic nerve's blood vessels. Some risk factors include age, race, family history and cardiovascular disease.

While intraocular pressure measurements are important, meticulous examination of the optic nerve by your doctor will determine if additional diagnostic tests are necessary. If glaucoma of any kind is suspected, the pressure is measured, photographs and tissue scans of the optic nerve are taken, corneal thickness is measured and a visual field test is performed to assess any loss of the patient's peripheral vision.

Typically, NTG is treated with eye drops taken one-to-two times per day, with periodic repeat testing to ensure the condition is not worsening. The clinical challenge is that about 10 percent of NTG patients will still suffer vision loss despite receiving the best treatments from the best doctors. Yet, for most, NTG progresses very slowly, and the majority of people do not have significant vision loss if treated properly.

Unfortunately, there is no cure for glaucoma, and early intervention remains the best way to preserve your vision. Periodic eye exams are recommended for people of all ages, especially those over age 60. At the end of each exam, make sure you ask your doctor if you have any diseases or what you can do to keep your eyes healthy. In general, exams every year or two, combined with a balanced diet and healthy lifestyle, are the best things you can do for your eyes.

David J. Weis, O.D. is a comprehensive eye care specialist at Milwaukee Eye Care Associates, Dr. Peter S. Foote is the medical director. Dr. Weis is currently accepting new patients. To schedule an appointment with Dr. Weis, or any of the providers at Milwaukee Eye Care Associates, please call 414-271-2020.