context: Glaucoma is a disease that damages the optic nerve, which connects your eye to your brain so you can see. The condition usally is due to too much pressure in the eye. But the "normal-tension" kind is different. There's a fluid that normally circulates around the front of your eye. With many kinds of glaucoma, that fluid doesn't drain as well as it should. So it backs up, much like water in a clogged drain. As a result, pressure builds up inside your eye. Over time, it starts to harm the optic nerve. But with normal-tension glaucoma, the optic nerve becomes damaged even though eye pressure stays within normal levels. Your doctor may call it "low-tension" or "normal-pressure" glaucoma. Doctors aren't sure why some people get normal-tension glaucoma. It may be that your optic nerve is more sensitive or fragile, so even normal amounts of pressure can damage it. The doctor should also ask whether you have had periods of abnormally low blood pressure either from excessive reaction to blood pressure medicine or from having had severe blood loss. This type of glaucoma also could be caused, in part, by not enough blood getting to your optic nerve. Poor blood flow can damage and eventually kill the cells that carry signals from your eye to your brain. A condition such as atherosclerosis, which is the buildup of fatty deposits in the arteries, can hamper how well your blood circulates. You're more likely to get this type of glaucoma if you: Have a family history of the condition Are of Japanese descent Have ever had heart disease You might not notice any problem in the early stages. Glaucoma is sometimes called a "silent thief of sight." Your optic nerve is like an electric cable. It's made up of more than a million tiny fibers, or "wires." As the nerve fibers die, you'll begin to get blind spots in your vision. But you may not notice them until most of your optic nerve fibers are dead. Without treatment, the first sign of normal-tension glaucoma is often the loss of your peripheral, or side, vision. You might start to miss things out of the corner of your eye. As the condition gets worse, your vision narrows. It's as if you're looking through a tunnel. If all the fibers in your optic nerve die, you become blind. Normal-tension glaucoma tends to worsen slowly. It's important to keep up with your regular eye exams with an ophthalmologist. That's a medical doctor who specializes in eye care and surgery. The exams can help find the disease before you lose vision. Your ophthalmologist will review your medical history and do a complete eye and vision exam. This will include taking your eye pressure. You'll get drops in your eyes to widen (or dilate) your pupils. Then your doctor will use a special magnifying glass to check the color and shape of your optic nerve. She'll also look for any damage or defects. The doctor will use different tests to measure the pressure inside your eye as well as the thickness of your cornea in the front of the eye. The ophthalmologist will also do what's called a visual field test to check for any losses in your peripheral vision that you may not notice yourself. Some people with normal-tension glaucoma have symptoms of blood vessel problems such as migraine headaches, cold hands and feet, or low blood pressure. Although glaucoma's damage can't be reversed, your doctor will try stop it from getting worse and slow or prevent more vision loss. She may prescribe eye drops, suggest laser treatment, or talk with you about surgery. Eye Drops These are usually the first step in glaucoma treatment. Some prescription drops cause your eye to make less fluid. That helps lower pressure. Other drops help the fluid drain from your eye better. Like all medicines, these may cause side effects, such as: Stinging or itchy eyes Blurry vision Changes in your pulse or heartbeat. Some drugs can cause problems when taken with other medications. Give your doctor a list of every medicine you take before you begin this treatment. Laser Treatment An eye surgeon will use a laser to unclog and open the drain holes in your eye. This way, fluid can flow out more easily and eye pressure will be reduced. You can get the laser treatment done in your ophthalmologist's office or an outpatient surgery center. Surgery If medicines and laser treatments don't control your eye pressure, your doctor may talk to you about different surgery options. One procedure, called a trabeculectomy, creates a new opening in the white of your eye (or sclera) for fluid to drain. Or you might be able to get a tiny drainage tube implanted in your eye to reduce pressure. Researchers are working to find the best treatment for normal-tension glaucoma that will help protect the optic nerve or improve blood flow to the nerve. Unfortunately, you can't prevent glaucoma. But blindness from the condition can often be prevented if it's diagnosed and treated early. So keep up with your regular eye exams done by an ophthalmologist.