The term ocular hypertension usually refers to any situation in which the pressure inside the eye, called intraocular pressure, is higher than normal. Eye pressure is measured in millimeters of mercury (mm Hg). Normal eye pressure ranges from 10-21 mm Hg. Ocular hypertension is an eye pressure of greater than 21 mm Hg.

Although its definition has evolved through the years, ocular hypertension is commonly defined as a condition with the following criteria:

• An intraocular pressure of greater than 21 mm Hg is measured in one or both eyes at two or more office visits. Pressure inside the eye is measured using an instrument called a tonometer.
• The optic nerve appears normal.
• No signs of glaucoma are evident on visual field testing, which is a test to assess your peripheral (or side) vision.
• To determine other possible causes for your high eye pressure, an ophthalmologist (a medical doctor who specializes in eye care and surgery) assesses whether your drainage system (called the “angle”) is open or closed. The angle is seen using a technique called gonioscopy. This technique involves the use of a special contact lens to examine the drainage angles (or channels) in your eyes to see if they are open, narrowed, or closed.
• No signs of any ocular disease are present. Some eye diseases can increase the pressure inside the eye.

Ocular hypertension should not be considered a disease by itself. Instead, ocular hypertension is a term that is used to describe individuals who should be observed more closely than the general population for the onset of glaucoma. For this reason, another term to refer to a person with ocular hypertension is “glaucoma suspect,” or someone whom the ophthalmologist is concerned may have or may develop glaucoma because of elevated pressure inside the eyes. An eye exam may show a glaucoma-damaged optic nerve.

As mentioned above, increased intraocular pressure can result from other eye conditions. However, within this article, ocular hypertension primarily refers to increased intraocular pressure without any optic nerve damage or vision loss. Glaucoma occurs when increased intraocular pressure, optic nerve damage, and vision loss are present.

Ocular Hypertension Causes

Elevated intraocular pressure is a concern in people with ocular hypertension because it is one of the main risk factors for glaucoma.

High pressure inside the eye is caused by an imbalance in the production and drainage of fluid in the eye (aqueous humor). The channels that normally drain the fluid from inside the eye do not function properly. More fluid is continually being produced but cannot be drained because of the improperly functioning drainage channels. This results in an increased amount of fluid inside the eye, thus raising the pressure.

Another way to think of high pressure inside the eye is to imagine a water balloon. The more water that is put into the balloon, the higher the pressure inside the balloon. The same situation exists with too much fluid inside the eye—the more fluid, the higher the pressure. Also, just like a water balloon can burst if too much water is put into it, the optic nerve in the eye can be damaged by too high of a pressure.

Medical Treatment:

The goal of medical treatment is to reduce the pressure before it causes glaucomatous loss of vision. Medical treatment is always initiated for those people who are believed to be at the greatest risk for developing glaucoma and for those with signs of optic nerve damage.

How your ophthalmologist chooses to treat you is highly individualized. Depending on your particular situation, you may be treated with medications or just observed. Your doctor will discuss the pros and cons of medical treatment versus observation with you.

• If you are experiencing symptoms like halos, blurred vision, or pain, or if your intraocular pressure has recently increased and then continues to increase on subsequent visits, your ophthalmologist will most likely start medical treatment.

Your intraocular pressure is evaluated periodically using these guidelines:

• If your intraocular pressure is 28 mm Hg or higher, you are treated with medicines. After 1 month of taking the drug, you have a follow-up visit with your ophthalmologist to see if the medicine is lowering the pressure and there are no side effects. If the drug is working, then follow-up visits are scheduled every 3-4 months.
• If your intraocular pressure is 26-27 mm Hg, the pressure is rechecked in 2-3 weeks after your initial visit. On your second visit, if the pressure is still within 3 mm Hg of the reading at the initial visit, then follow-up visits are scheduled every 3-4 months. If the pressure is lower on your second visit, then the length of time between follow-up visits is longer and is determined by your ophthalmologist. At least once a year, visual field testing is done and your optic nerve is examined.
• If your intraocular pressure is 22-25 mm Hg, the pressure is rechecked in 2-3 months. At the second visit, if the pressure is still within 3 mm Hg of the reading at the initial visit, then your next visit is in 6 months and includes visual field testing and an optic nerve examination. Testing is repeated at least yearly.