Tonometry

Glaucoma Screening Test

How It Is Done

Tonometry takes only a few minutes to do.

Applanation (Goldmann) method

This type of tonometry is done by an ophthalmologist or an optometrist. Your doctor will use eyedrops to numb the surface of your eyes so that you will not feel the tonometer during the test. A strip of paper containing a dye (fluorescein) will be touched to your eye, or eyedrops containing the dye will be applied. The dye makes it easier for your doctor to see your cornea.

You will rest your chin on a padded support and stare straight into the microscope (slit lamp). Your doctor sits in front of you and shines a bright light into your eye. Your doctor gently touches the tonometer probe to your eye. Your doctor checks the tension dial on the tonometer that measures the IOP of your eye.

Do not rub your eyes for 30 minutes until the numbing medicine has worn off.

Electronic indentation method

Electronic tonometry can be done by a technician, an optometrist, an ophthalmologist, or a family medicine doctor. Your doctor will use eyedrops to numb the surface of your eyes so that you will not feel the tonometer during the test.

You will rest your chin on a padded support and stare straight ahead. Your doctor gently touches the tonometer probe to your eye. Four readings will be taken on each eye. You will hear a clicking sound each time an accurate reading is obtained. After four accurate readings, a beep will sound, and the averaged IOP measurement will appear on the instrument's display panel.

Do not rub your eyes for 30 minutes until the numbing medicine has worn off.

Noncontact (or air-puff) method

This type of tonometry is done by an ophthalmologist or an optometrist. You do not need drops to numb your eye for this method.

You will rest your chin on a padded support and stare straight into the microscope (slit lamp). Your doctor sits in front of you and shines a bright light into your eye. A brief puff of air is blown at your eye. You will hear the puffing sound and feel a coolness or mild pressure on your eye. The tonometer records the intraocular pressure (IOP) from the change in the light reflected off the cornea as it is indented by the air puff. The test may be done several times for each eye.

Indentation (Schiotz) method

This type of tonometry is usually done by an ophthalmologist or an optometrist. Your doctor will use eyedrops to numb the surface of your eyes so that you will not feel the tonometer during the test.

You will lie on your back on an examination table. Try to stay relaxed and not cough, blink, or squeeze your eyelids together because these movements can increase the pressure inside your eyes.

You will look up at a spot on the ceiling. Your doctor will gently touch the tonometer to your eye and hold it there for a few seconds. The test may be done on the other eye also.

Do not rub your eyes for 30 minutes until the numbing medicine has worn off.

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Author:	Jeannette Curtis	Last Updated: April 8, 2008
Medical Review:	Kathleen Romito, MD - Family Medicine Christopher J. Rudnisky, MD, FRCSC - Ophthalmology
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