A tonometer is
an instrument that is used to estimate intraocular pressure which is the fluid
pressure behind the eye. Most tonometers are calibrated to measure pressure in
millimeters of mercury. It can measure either the degree of corneal deformation
produced by a known force, or the force needed to produce a given degree of
corneal deformation. Optometrists often use these to screen for certain
conditions and monitor those with known eye problems, particularly that of
glaucoma. Glaucoma is an eye disease in which the optic nerve is damaged in a
characteristic pattern. This can lead to permanent damage and affect vision in
the affected eye, eventually leading to blindness if left untreated. Because of
the risks involved, the test is often included as a routine eye pressure test
as it is vital to diagnose and treat glaucoma as soon as possible.
There are various methods of tonometry and each ophthalmologist and/or
optometrist determines which method to use for an eye pressure test. These
methods include Applanation tonometry, Goldmann tonometry, Perkins tonometry,
Dynamic Contour tonometry, Non-contact tonometry, Ocular response analyzer,
Electronic indentation tonometry, Rebound tonometry and Pneumatonometry to name
Goldmann tonometry is considered to be the most accurate as well as the most
widely accepted method. Numbing eye drops are used prior to the procedure to
alleviate any discomfort. A small probe is then used to flatten a portion of
the cornea. The eye care professional will evaluate your cornea while looking
through a microscope. The force needed to flatten the cornea then determines
the eye pressure. Usually this test is done after utilizing air-puff tonometry.
These two tests are usually enough to determine the eye pressure.
The accuracy of a tonometer reading is usually determined by several factors.
People have slight differences in the thickness and hardness of their corneas,
so a person with a particularly hard cornea might have an abnormally high IOP
reading but still be healthy. Many factors can attribute to a person's IOP. Eye
inflammation, illness, diet and exercise also determine a person's IOP. It is
hard for some patients to remain still during the procedure so in these
instances air puff, Icare, or Diaton tonometers are used. This occurs mostly
with people who do not like things touching the eye and with children.
Eye care is very important in order to maintain quality of life and should not
be neglected for any reason.