Normal-tension glaucoma is a type of glaucoma in which the optic nerve damage and vision loss occur even though there are normal levels of tension in the eye. Typically, glaucoma is caused by high eye pressure, which leads to damage of the optic nerve, but in normal-tension glaucoma, this is not the case.
Eye pressure, known as intraocular pressure, is measured in millimeters of mercury, just like your blood pressure. A normal eye pressure reading is between 10 to 21 mm Hg. Typical glaucoma patient’s readings of eye pressure are over 21 mm Hg, but in normal-tension glaucoma readings are appear to be normal, yet damage still exists.
Normal-tension glaucoma is similar to primary open-angle glaucoma. In the U.S., 15 to 25 percent of glaucoma patients have normal-tension glaucoma.
Normal-tension glaucoma isn’t completely understood. It is believed to be caused by either an unusual fragile optic nerve that can still become damaged under normal pressure or a reduction in blood flow to the eyes.
Many patients with normal-tension glaucoma do not experience any symptoms. This can be problematic, because by the time it is caught by your eye specialist it may have already progressed quite a bit. It’s important to go for regular eye exams in order to check for any changes in your vision or eye pressure.
Patients may experience some level of vision loss as the disease progresses, and at that point there is already a significant amount of damage to the optic nerve. In this case, the damage to the optic nerve and vision loss are permanent.
As mentioned, the best way to be tested for normal-tension glaucoma is through a regular eye exam. Your eye doctor can measure your eye pressure, including optic blood pressure, in order to rule out ocular hypertension.
Another test your doctor can perform is a gonioscopy, which checks for drainage angle in the eye. To complete this test, the doctor places a contact lens on the eye. The results reveal if the angles of the eye are open, narrowed, or closed.
Other tests include imaging tests, fundus photographs, retina examination, and visual field testing which checks the peripheral vision of the patient.
There are many different treatments for normal-tension glaucoma, depending on severity of the condition. For starters, your doctor may prescribe medications to reduce pressure in the eye. Following your doctor’s instructions is integral for a favorable outcome. These medications may come in the form of eye drops and have been found to reduce eye pressure by 30 percent.
Another option for normal-tension glaucoma is surgery, which is known as trabeculoplasty. During this procedure, a laser beam is placed in the small spots of the trabecular meshwork, further opening them up to allow greater drainage of the fluid to reduce pressure.
For proper treatment, at least 100 different spots are placed over the entire trabecular meshwork. This type of procedure may be split up into two sessions. The procedure takes about 30 minutes or less and is relatively painless.
Although this procedure is effective, the effect is temporary and only lasts about three to five years. In addition to this procedure, you will be prescribed anti-inflammatories, along with your regular glaucoma medications.
After any procedure or treatment, you will still be required to attend follow-up appointments for your normal-tension glaucoma to monitor progress. These appointments may be scheduled every three to six months.