Reasons you may not be able to
have the test or why the results may not be helpful include:
Having a sore on your eye or an eye infection.
This increases your risk of an eye injury during the test.
nearsighted, having an irregularly shaped cornea, or
having had major eye surgery in the past.
Blinking or squeezing
your eyes shut during the test.
Having had laser refractive surgery
(such as LASIK).
What To Think About
Tonometry tests may be done over months or
years to check for glaucoma. Also, because intraocular pressure (IOP) can
change at different times of the day, tonometry is not the only test done to
check for glaucoma. If the IOP is high, more tests, such as ophthalmoscopy,
gonioscopy, and visual field testing, may be done. For more information, see
ultrasound to measure the thickness of the cornea. The thickness of the cornea
can affect IOP measurement. Pachymetry is often done during a tonometry test.
It can help your doctor know your chance for developing glaucoma.
Normal IOP is different from person to person. About 40% to 50% of people who
have optic nerve damage caused by glaucoma have normal IOP.1, 2 In some cases of glaucoma there is
damage to the optic nerve even though the eye pressure is never above
Shah R, Wormald R (2009). Glaucoma, search date November 2007. Online version of BMJ Clinical Evidence: http://www.clinicalevidence.com.
Trobe JD (2006). Principal ophthalmic conditions.
Physician's Guide to Eye Care, 3rd ed., chap. 6, pp.
107-111. San Francisco: American Academy of Ophthalmology.
Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis:
Primary Medical Reviewer
Kathleen Romito, MD - Family Medicine
Specialist Medical Reviewer
Christopher J. Rudnisky, MD, MPH, FRCSC - Ophthalmology