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Tonometry

Ocular tonometry is a diagnostic test performed to measure the Intraocular pressure and detect injuries that could affect the optic nerve. It is a simple and non-invasive test.

There are different types of tonometry in order to adapt to both the patient's conditions and the needs of the ophthalmologist.

En Área Oftalmológica Avanzada We explain what a tonometry is and how it is performed.

What is an ocular tonometry?

El vitreous humor and aqueous humor are substances that exert pressure on the rigid structures of the eye, this pressure is what is defined as intraocular pressure.

In general, intraocular pressure should be maintained in a range between 10 to 21 mmHG in normal values.

A significant increase in eye pressure may be a sign of glaucoma, a pathology that affects the optic nerve in a very important way.

Tonometry is the diagnostic test that measures the intraocular pressure of the eye and diagnoses the glaucoma.

Types of tonometry

When measuring intraocular pressure, different procedures can be established, which are:

air tonometry

It is also known as non-contact tonometry, pneumatic tonometry or pneumotonometry.

This test is performed through a tonometer that blows air into the patient's eye to flatten the cornea.

With the cornea completely flattened in the central part, the air tonometer proceeds to measure the intraocular pressure.

The more air pressure the tonometer has to emit to flatten the central part of the cornea, the higher the value of IOP or intraocular pressure that will give us as a result of the diagnostic test.

The air tonometer is the least accurate type of tonometry, because the breath of air can cause the patient to close their eyes or blink, which can give us abnormal results of intraocular pressure.

Air or non-contact tonometry is not recommended in people with corneal scarring.

Applanation or Goldman tonometry

This type of ocular tonometry measures eye pressure indirectly with the help of a tonometer placed in a slit lamp.

It is required that the patient supports the head in the slit lamp where the diagnostic test will be performed.

To perform applanation or Goldman tonometry, we will require the instillation of a dye (fluorescein) and an anesthetic eye drop, since to perform this test it is necessary to contact a small cone with the cornea to measure the IOP or intraocular pressure.

Currently, it is the most widely used technique in ophthalmology.

Perkins Applanation Tonometry

It is carried out with the Perkins tonometer, a portable device that allows pressure to be measured without the need for a slit lamp.

In order to measure the IOP, as with the applanation tonometer, we will need to instill fluorescein (dye) and anesthetic drops because there is direct contact with the eye.

Experts recommend practicing the use of the Perkins system several times in order to obtain accurate results because despite having a small platform to support the patient's head, it is done by free hand.

This Perkins applanation tonometry is especially useful in hospitals where the ophthalmologist must examine patients who cannot move.

rebound tonometry

It is the newest technique. The measurement is performed through the emission of a metal probe that is placed perpendicular to the cornea.

As the probe comes into contact with the cornea, it slows down and bounces off the cornea. At this time the tonometer measures the pressure it is exerting on the cornea.

The value of intraocular pressure that it provides us is proportional to the deceleration value of the probe when it comes into contact with the eye.

How is tonometry performed?

The procedure varies depending on the type of exam being performed.

The type of tonometry that offers the most accurate results and is most used by ophthalmologists is applanation or Goldman tonometry.

To perform this technique, the doctor must apply a few drops of anesthesia on the patient's eyes and, in addition, fluorescent dye is used to dye the yellow tears.

Once the patient is anesthetized, they should remain seated and rest their chin on the slit lamp chinrest without closing their eyes.

Then, the doctor will proceed to place the tonometer's biomicroscope in the front area of ​​the eye to perform the measurement.

The examination is carried out in a semi-dark room.

When is a tonometry recommended?

Tonometry is the test that most accurately measures IOP or intraocular pressure, therefore it must be performed in a Ophthalmological examination complete, especially as long as the doctor wants to diagnose glaucoma.

After 40 years of age, a person's risk of suffering from glaucoma increases, therefore, it is important to include ocular tonometry in the annual ophthalmological examination to diagnose this disease in time.

It can also be indicated before or after eye surgery to carry out a more precise follow-up of the patient's evolution.

Do you want to know more about ocular tonometry and its procedure? Get in contact with us! In Área Oftalmológica Avanzada, our professionals will be delighted to receive your inquiry.

Summary
Tonometry
Article name
Tonometry
Description
Tonometry is a simple, non-invasive test performed by an ophthalmologist. We tell you what it is for and how it can be done.
Author
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Área Oftalmológica Avanzada
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Synonyms:
tonometry, ocular tonometry
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