Skip Navigation Links



    Learn More     Subscribe    
Join Now!      Login
Walking Quiz
Which of the following in NOT a direct benefit of a regular walking regimen?
hat Doctors Don't Tell You

© What Doctors Don't Tell You (Volume 15, Issue 7)

Tonometry An early warning for glaucoma, this simple test can detect low eye pressure, or IOP (intraocular pressure), an indicator of other eye disorders such as inflammation, a detached retina and a poor blood supply to the eye. It’s quick, and usually carried out by an ophthalmologist, but it’s also notoriously unreliable.

Tonometry comes in three varieties. The most accurate is the Goldmann applanation method, which measures the amount of force necessary to flatten the cornea; the higher the IOP, the greater the force needed. Another option is Schiotz, or indentation, tonometry, which uses a preset amount of weight to gently press a plunger into the cornea, making a slight indentation. The third method is non-contact, or air-puff, tonometry, in which a puffer blasts air at the cornea, and the rebound air is then measured. Considered the most inaccurate of the three, it is also the least invasive.

Topical anaesthetic eyedrops are used with both applanation and Schiotz tonometry, with applanation also using eyedrops containing a special dye called ‘fluorescein’. As this dye can permanently stain contact lenses, these should be removed before taking the test. The ophthalmologist should also check if you have an irregularly shaped or deformed cornea - in which case, a special tonometer will need to be used. Regardless of method, the test takes just a couple of minutes, although it may take several hours before the anaesthetic wears off.

Is it accurate? As tonometry is unreliable, researchers usually stress that the test needs to be carried out as part of a general eye examination, which may reveal problems more readily than tonometry can. Ophthalmologists who rely on tonometry alone to determine whether to carry out a more exhaustive examination may be doing the patient a great disservice.

One study tested all three types of tonometry, and found that none was entirely successful in detecting problems with eyes with known conditions. Although the most accurate was the Goldmann method, even this was not sensitive across the entire range of pressures tested. Ophthalmologists would still need to check the optic nerve and visual field to be sure of a diagnosis of glaucoma (Br J Ophthalmol, 1997; 81: 448-51).

A study by the Moorfields Eye Hospital in London arrived at similar conclusions. In this case, they concentrated only on the applanation test (Eye, 2002; 16: 562-6).

Is it safe? If the test is unreliable, it is at least safe, or so the eye specialists maintain. The worst that can happen is a slight scratching of the cornea, but this will heal within 24 hours or so, they say. The dye used in the Goldmann applanation test is also relatively harmless, though it can permanently discolour contact lenses.

However, there is a risk that Creutzfeldt-Jakob disease can be contracted from the tonometry equipment (see box above).

Add your comment      
About The Author
What Doctors Don’t Tell You is one of the few publications in the world that can justifiably claim to solve people's health problems - and even save lives. Our monthly newsletter gives you the facts you won't read anywhere else about what works, what doesn't work and what may harm you in both orthodox and alternative medicine. We'll also tell you how you can prevent illness.......more
Related Articles
Share   Facebook   Buzz   Delicious   Digg   Twitter  
From Our Sponsor
Featured Events
Wellness Inventory Certification Training
     September 16-December 16, 2014
     Teleclass, CA USA
Additional Calendar Links
Wellness, Eating, dimension!

Home       Wellness       Health A-Z       Alternative Therapies       Find a Practitioner       Healthy Products       Bookstore       Wellness Inventory
Healthy Kitchen       Healthy Woman       Healthy Man       Healthy Child       Healthy Aging       Wellness Center       Nutrition Center       Fitness Center
Free Newsletter      What Doctor's Don't Tell You      Discount Lab Tests      First Aid      Global Health Calendar      Privacy Policy     Contact Us

Disclaimer: The information provided on HealthWorld Online is for educational purposes only and IS NOT intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek professional medical advice from your physician or other qualified healthcare provider with any questions you may have regarding a medical condition.