How Is Eye Pressure Measured?


Quick Answer

Eye pressure is measured through one of several tonometry procedures. In most procedures, the eye is numbed first to ease any discomfort. In the applanation procedure, the cornea of the eye is gently flattened by a probe, and the doctor uses a slit lamp microscope to examine the eye.

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Another type of tonometry uses electronic indentation. An instrument is placed on the cornea, and the results are read on a computer. Pneumotonometry uses a puff of air to measure eye pressure. The air flattens the cornea for a short period. This process is the least accurate type of tonometry, but it is useful to check the eye pressure in children and to test for very high eye pressure. It also does not require numbing eyedrops.

Eye pressure is measured in millimeters of mercury, and normal eye pressure for an adult is 10 to 21 mmHg. Any reading more than 21 mmHg means that the pressure in the eye is so high that it puts a person at risk for glaucoma. Glaucoma occurs when eye pressure is so high that it damages the optic nerve. This condition is a leading cause of blindness.

Medications such as eyedrops are prescribed to reduce high eye pressure, and laser surgery is possible if medications are not successful.

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