Tonometry

Alternative Names:Intraocular pressure (IOP) measurement; Glaucoma test
Definition:
Tonometry is the measurement of tension or pressure  in your eyeball. High pressure inside the eye is caused by a disease called glaucoma, which can damage your vision if it is not treated. It is recommended that all adults over age 40 have their eye pressures measured every three to five years to check for glaucoma.Because People over age 40, especially African-Americans, are at the highest risk for developing glaucoma. Regular eye exams can help detect glaucoma early, when it can usually be treated.

A tonometer is an instrument for measuring tension or pressure ……..CLICK & SEE

In ophthalmology, tonometry is the procedure eye care professionals perform to determine the intraocular pressure (IOP), the fluid pressure inside the eye. It is an important test in the evaluation of ocular conditions such as glaucoma as well as conditions such as phthisis bulbi, and iritis. Most tonometers are calibrated to measure pressure in mmHg.
How do you prepare for the test?
Remove any contact lenses before the examination.The dye can permanently stain contact lenses.  Inform the health care provider if you have corneal ulcers and infections, an eye infection, if you are taking any drugs, or if you have a history of glaucoma in your family or other type of eye problem.
What happens when the test is performed and how it is done?
The pressure inside your eye is always measured from the outside. In most cases, if you are at an eye clinic, the pressure can even be measured without anything actually touching your eye. The eye doctor has you look up close at an instrument that blows a small puff of air onto your eye. It then uses a special sensor (like a tiny radar detector) to detect the amount of indentation that the air puff causes on the surface of the eye. This indentation is normal and lasts for only a fraction of a second.

Sometimes patients need to have their eye pressure measured but they are not in an eye clinic with this type of machine (for example, some patients need to be checked for glaucoma in an emergency room). In this case, the pressure can be measured with an instrument resembling a pen. One end of the instrument is placed on the surface of the eyeball. This feels like having a contact lens put in your eye.

There are several methods of testing for glaucoma.

The applanation method measures the force required to flatten a certain area of the cornea. A fine strip of paper stained with orange dye is touched to the side of the eye. The dye stains the front of the eye to help with the examination, then rinses out with tears. An anesthetic drop is also placed in the eye.

The slit-lamp is placed in front of you and you rest your chin and forehead on a support that keeps your head steady. The lamp is moved forward until the tonometer touches the cornea. The light is usually a blue circle. The health care provider looks through the eyepiece on the lamp and adjusts the tension on the tonometer. There is no discomfort associated with the test.

A slightly different method of applanation uses an object similar to pencil. Again, you are given numbing eye drops to prevent any discomfort. The device touches the outside of the eye and instantly records eye pressure.

The last method is the noncontact method (air puff). In this method, your chin rests on a padded stand. You stare straight into the examining device. The eye doctor shines a bright light into your eye to properly line up the instrument, and then delivers a brief puff of air at your eye. The machine measures eye pressure by looking at how the light reflections change as the air hits the eye.

Must you do anything special after the test is over?
Nothing.
How the Test Will Feel?
If numbing eye drops were used, you should not have any pain. In the noncontact method, you may feel mild pressure on your eye.

What risks are there from the test?
The test might make you feel like blinking, but it does not cause any pain. There are no risks from this test.If the applanation method is used, there is a small chance the cornea may be scratched (corneal abrasion). This will normally heal itself within a few days.

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How long is it before the result of the test is known?
You can know the result of the test right away.

Results:

Normal Results

The eye pressure is within the normal range.

Normal eye pressure range is 10 – 21 mm Hg.

What Abnormal Results Mean?

Glaucoma may be detected.

Additional conditions under which the test may be performed:

Hyphema
*Trauma to the eye or head
*Before and after eye surgery

Resources:
http://en.wikipedia.org/wiki/Tonometry
https://www.health.harvard.edu/diagnostic-tests/tonometry.htm
http://www.nlm.nih.gov/medlineplus/ency/article/003447.htm

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One thought on “Tonometry”

  1. Glaucoma is the third largest cause for blindness worldwide. It is responsible for blindness in 5.2 million people across the globe. The earlier the disease is diagnosed and treated, better will be the results of treatment, as the damage caused by glaucoma cannot be reversed. Glaucoma is treated either with medication or through surgery, depending on the severity of the case. Visit here Glaucoma- The silent thief of vision

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