TONOMETRY

 

Tonometry is a standard test performed by an ophthalmologist or optometrist. Its purpose is to determine the fluid pressure inside the eye. The medical term for this is intraocular pressure (IOP).

Increased IOP is a major risk factor for developing glaucoma, an eye disease that potentially can be very serious if it is not detected and treated promptly.

IOP is measured using one of two major methods.

1. Applanation Tonometry. This test involves mounting a special disinfected prism tip on the tonometer head and then placing it against the cornea. The examiner then uses a cobalt blue filter to view two green semicircles. The force applied to the tonometer head is then adjusted using a dial until the inner edges of these green semicircles meet. Because the probe makes contact with the cornea, eye drops are used to introduce an anesthetic onto the surface of the eye. Thickness of the cornea can influence accuracy of the intraocular pressure measurement.
2. Non-Contact Tonometry. Also known as an "air-puff test", this type of tonometry uses a rapid air pulse to flatten the cornea and therefore does not require that the surface of the cornea be touched. Intraocular pressure is estimated by detecting the force of the air jet at the instance of applanation (flattening of the cornea). This eye pressure test tends to underestimate intraocular pressure when it is high and to overestimate it when it is low.

Adults over age 40 should have IOP measured in both eyes every 2-3 years and more often if they have risk factors for glaucoma.

 

Additional Information about Tonometry

Tonometry from the National Institutes of Health (USA)

IOP and Tonometry from the American Academy of Ophthalmology

Tonometry - book chapter by Patrick C. Alguire, appearing in Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990.

Can An Applanation Tonometry Test Cause Eye Infections? from glaucoma-eye-info.com

 

Related Topics

Glaucoma Suspect

Neovascularization

Ocular Hypertension

Ophthalmology

 

 

 

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