Can An Applanation Tonometry Test Cause Eye Infections?Ophthalmologist Carolina Valdivia MD discusses the potential for eye infections from an applanation tonometry test that is used to assess eye pressure.  A 55 year-old woman from India writes:Dear Dr. Valdivia, Is there any non-invasive and non-eye-drops eye pressure test to check the eyes for glaucoma? I have cloudiness in my right eye and I am afraid of contracting eye infections later.
The gold standard for measuring intraocular pressure in a laboratory environment is ocular manometry. However, this is an invasive procedure that measures pressure inside the eye directly and is not practical at the office of an ophthalmologist. Instead, an indirect (non-invasive) method called applanation tonometry is used to measure intraocular pressure at your eye doctor's office. I present examples of different types of tonometry below in order of highest to lowest accuracy.
Each tonometry test listed above works by applanation, which involves temporarily flattening the convex surface of the cornea and correlating this with the pressure inside the eye. The difference in methods relates to the means by which the flattening is accomplished. Additionally, some factors may influence the precise outcome of the eye pressure test, such as the thickness and shape of the cornea. Goldmann Applanation Tonometry
Measuring intraocular pressure using a Goldmann Applanation Tonometry test involves mounting a special disinfected prism tip on the tonometer head and then touching it against the cornea.
Because the probe makes contact with the cornea, eye drops are used to introduce an anesthetic onto the surface of the eye. The prism tip must be disinfected prior to each use. If it is disinfected properly, the probability of contamination or later eye infections is zero. Patients sometimes complain of blurred vision after the examination, but this clears up quickly.
Historically, non-contact tonometry has been used for large-scale population screening efforts because the eye pressure test is fast and simple. However, once elevated intraocular pressure is detected, a more accurate form of tonometry typically is used for continuous monitoring. Since a non-contact tonometry test is accomplished without the instrument contacting the cornea, the potential for disease transmission and later eye infections is reduced. Although the decision to use non-contact tonometry to monitor your glaucoma is one that you should make in conjunction with your eye doctor, I would not recommend it to my glaucoma patients as a good method for the regular monitoring of intraocular pressure. Tono Pen Pascal Dynamic Contour Tonometer In general, a contact tonometry test is more accurate. Among these, the Goldmann Applanation Tonometer is recommended for monitoring a person with glaucoma. Together with pachymetry, which is the measurement of corneal thickness to fine tune results of the intraocular pressure measurement, this tool is the most reliable and accurate eye pressure test. As I mention above, patients sometimes report blurred vision following an examination using contact tonometry. This is because the process of applanation temporarily deforms the cornea and affects its refracting power. This is a transient phenomenon and patients quickly recover as the cornea regains its normal shape. Eye infections involving the cornea are rare, but can be serious. The most common cause is the improper use of contact lenses. Eye infections introduced by contact tonometry would be very rare and require 24 hours or more before symptoms appear. Symptoms of corneal eye infections include eye burning, itching, redness, and discharge. There also may be blurred vision and sensitivity to light. If these symptoms are experienced, you should see an ophthalmologist for diagnosis and treatment immediately. Carolina Valdivia, MD
REFERENCECrick RP and Khaw PT. Textbook of Clinical Ophthalmology, 3rd Ed. River Edge, New Jersey: World Scientific, 2003:555-560.
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Return from Applanation Tonometry to Answer My Health Question
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Thank you for your important question. Contracting eye infections from an eye pressure test is a concern that many people have. I am grateful for your support of glaucoma-eye-info.com.
