Encyclopedia - Ocular Hypertension

Who is at risk for ocular hypertension?
What causes ocular hypertension?
How is ocular hypertension checked?

Ocular hypertension occurs when the intraocular pressure in your eyes is above the normal range, but it has not yet affected your vision or damaged the structure of your eyes. Normal eye pressure usually ranges between 10 and 21 mm of mercury. Pressure consistently above 21 indicates ocular hypertension. The condition can develop into glaucoma, a serious disease that causes damage to the optic nerve.

Who is at risk for ocular hypertension?

Most at risk for developing ocular hypertension are African Americans and those with a family history of the condition. It is also more common in those who are nearsighted, have high blood pressure, or are diabetic. Because ocular hypertension has no outward symptoms, people over the age of 40 and those in a high-risk category for glaucoma should have their pressure checked every year. A pressure check is a painless procedure that is part of any comprehensive eye examination.

What causes ocular hypertension?

In simple terms, ocular hypertension is caused by an excessive buildup of fluid inside the eye. This fluid, or aqueous humor, nourishes the cornea, iris, and lens (See Anatomy of the Eye), and maintains intraocular pressure. The typical eye produces about 4 c.c. of fluid a day, which circulates and then drains out of the eye If the drainage system becomes clogged or if too much fluid is produced, pressure inside the eye can build up. The reasons for this are not fully understood.

There are normally no symptoms of ocular hypertension, which is one of the reasons why regular eye examinations are so important. Although ocular hypertension in itself is not sight threatening, if pressure within the eye builds to the point where it damages the optic nerve (glaucoma), eyesight can be permanently damaged.

How is ocular hypertension checked?

An instrument called a tonometer is used to check eye pressure. There are two types of tonometers. One is called an applanation tonometer and uses an instrument that looks somewhat like a pen. After numbing eyedrops are administered, the instrument is applied gently to the front surface of the eye and provides a pressure reading. The other type is a noncontact tonometer, which directs a warm puff of air toward the eye without touching it.

Neither ocular hypertension nor glaucoma can be prevented or cured, and ocular hypertension does not usually require treatment unless it progresses to glaucoma. Some doctors may, however, treat the condition with eye drops or other medicines as a precautionary measure. After you are diagnosed with ocular hypertension, your eye health must be monitored closely.