There are four different types of test that can help detect glaucoma. Each test measures the pressure inside your eye, also known as intraocular pressure, by determining the resistance of your cornea to indentation. Nothing says fun like getting poked in the eye!
Non-contact tonometry, also known as pneumotonometry, uses a puff of air to flatten your cornea. This is the least accurate but easiest tonometry test out there. It basically screens only for high intraocular pressure. If you’ve been in for an eye exam, you’ve probably had the air-puff eye test. Personally, it’s my least favorite part of the experience.
Applanation tonometry uses a special probe to flatten part of the cornea to measure pressure. The doctor will apply a numbing agent first, don’t worry. A slit lamp microscope will examine the eye; this test is often used as a follow-up if the air-puff test detects high levels of intraocular pressure.
Indentation tonometry uses a plunger to indent your cornea. This one isn’t as popular among optometrists and ophthalmologists, but may be used by emergency care doctors or family practitioners to measure pressure inside the eye. Eye drops will numb your eye before the test is done.
Electronic indentation tonometry uses a pen-like instrument to indent the cornea and transmit your readings to an LCD panel. Your eye doctor will give you numbing eye drops before the test so you don’t feel anything.
Be sure to talk to your doctor if you or someone in your family has glaucoma. Take out your contact lenses before your eye exam, and leave them out for a few hours after the test. The hardest part is trying to relax — it’s hard to stay still when you KNOW somebody is going to be touching your eye. But pressure on the veins in your neck (from tension) can increase the pressure inside your eyes and possible give a false pressure reading.
Normal eye pressure varies from one person to another. An average person has intraocular pressure between 10 and 21 millimeters of mercury. More than 21 mm HG is considered abnormal or high pressure.
Read more about safe driving as you (and your eyes) age.