Screening for glaucoma

A test measures your intraocular pressure (tonometry) — the fluid pressure inside your eyes. It helps your eye doctor detect glaucoma, a disease that damages the optic nerve. However, eye pressure measurement is just one thing your eye doctor considers when determining your risk of glaucoma. It's possible to have higher than average eye pressure and not have glaucoma or to have glaucoma if you have normal eye pressure. Your eye doctor will also carefully evaluate your optic nerve for signs of damage.

Methods your eye doctor may use to measure intraocular pressure include:

  • Applanation tonometry. This test measures the amount of force needed to temporarily flatten a part of your cornea. Fluorescein, the same dye used in a regular slit-lamp exam, is usually put in your eye to make your eye easier to see. You'll also receive eyedrops containing an anesthetic. Using the slit lamp, your doctor moves the tonometer to touch your cornea and determine the eye pressure. Because your eye is numbed, you won't feel anything.
  • Noncontact tonometry. This method uses a puff of air to estimate the pressure in your eye. No instruments will touch your eye, so you won't need an anesthetic. You'll feel a momentary pulse of air on your eye, which can be a surprising.

If your eye pressure is higher than average or your optic nerve looks unusual, you doctor may use pachymetry. This test uses sound waves to measure the thickness of your cornea. The most common way of measuring corneal thickness is to put an anesthetic drop in your eye, then place a small probe in contact with the front surface of the eye. The measurement takes seconds.

You may need more-specialized tests, depending on your age, medical history and risk of developing eye disease.