Understanding the Principle and the Functions of Applanation Tonometers

Tonometry is an eye test that can distinguish changes in eye pressure sometime before you might know about them.

The most well-known kind of tonometry test is known as the “Goldmann applanation tonometry test.” It has been viewed as the global highest quality level for estimating eye pressure for quite a long time. It includes utilizing a level-tipped test that is delicately squeezed against the outer layer of your eye.

There are a few different techniques for testing for eye pressure. These incorporate an elective kind called non-contact tonometry and utilize the Tono-Pen. These tests are generally thought to be less exact than Goldmann applanation tonometry. In non-contact tonometry, pneumatic force is applied to your eye utilizing an instrument that somewhat straightens the cornea.

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The principle upon which Applanation Tonometer works

The exact measurement of intraocular pressure (IOP) is essential in the finding and follow-up of glaucoma since IOP stays the central treatable gamble considering the administration of glaucoma.

The Goldmann applanation tonometer (GAT) is presently the most generally involved gadget in the clinical setting and is viewed as the best quality level for IOP estimation.

Applanation tonometry depends on the Imbert-Fick guideline, which expresses that the strain inside a perfect, dry, dainty walled circle rises to power, which is vital to smooth its surface isolated by the area of leveling (P = F/A, where P = pressure, F = force, and A = region).

In applanation tonometry, the cornea is leveled, and the Intraocular Pressure is calculated by varying the applanating force or the area of the cornea flattened.

The Maklakoff tonometer was an early illustration of this strategy, while the Goldmann tonometer is the most generally involved rendition in current practice. Because the test connects with the cornea, an effective sedative, for example, proxymetacaine, is acquainted with the eye’s outer layer as an eye drop.

Data and statistics of the market trend of tonometers.

The primary consideration credited to the development of the concentrated market is the rising frequency of glaucoma and the rising geriatric populace and diabetic patients who are more inclined to suffer from glaucoma shortly.

Glaucoma Research Foundation (2020) states that around 3 million Americans live with glaucoma, and 19% of all visual impairment among African Americans is related to open-point glaucoma.

As per an exploration concentrated by Gabriela Thomassiny et al., distributed in ARVO Journal in June 2020, glaucoma is one of the primary sources of visual deficiency in Latin America. Latin Americans have an expanded gamble of creating glaucoma.

Around 75% of the impacted populace is undiscovered, and Mexico is the second most populated country in Latin America. The investigation results discovered that in Mexico, in 2030, the number of individuals with glaucoma will probably be 2.5 million, expanding to 3 million by 2040 and 3.4 million by 2050. Expanding mindfulness among patients about early findings and routine checking of intraocular pressure (IOP) to forestall avoidable vision misfortune is expected to drive the market soon.

Consequently, the high frequency of glaucoma is supposed to drive the interest in tonometer gadgets. Giving positive repayment approaches to tonometers is supposed to help its reception rate in clinics and medical facilities.

Functionality of Goldmann and Perkins applanation tonometers

The Goldmann applanation tonometer estimates the force essential to straighten a corneal area of 3.06mm width. At this measurement, the cornea’s obstruction to leveling is offset by the slender fascination of the tear film meniscus for the tonometer head.

The IOP (in mmHg) approaches the smoothing force (in grams) duplicated by 10. The fluorescent color is put on the patient’s eye to feature the tear film. A split-picture crystal is utilized to partition the attacked picture into an unrivaled and a substandard circular segment. The intraocular pressure is taken when these bends are adjusted to contact their internal edges.

Applanation tonometry estimations are impacted by the central corneal thickness (CCT). When Goldmann planned his tonometer, he assessed a standard corneal thickness of 520 microns to drop the contradicting force of surface pressure and unbending corneal nature to permit space.

It is currently realized that a wide variety exists in corneal thickness among people. Thicker CCT might give a misleadingly high IOP estimation, while more slender CCT can give a falsely low reading.

Different mistakes that might influence the precision and accuracy of readings from a Goldmann tonometer include excessive or lacking amount of fluorescein dye for the tear film to influence the thickness of the covering curves, high astigmatism, and unpredictable or scarred cornea.

Even some excessive pressure from a finger on the eyelid while taking the calculation and breath-holding or Valsalva move by the patient during estimation can also affect the readings of the Goldmann tonometer.

The Perkins tonometer is a convenient Goldmann applanation tonometer that can be utilized with the patient in either the upstanding or prostrate positions.


This is all you need to know about the Principle and the Functions of Applanation Tonometers. Almagia International offers Easyton Tonometer that offers next-level treatment in the study with the Goldmann method. This method has been used as a reference standard.

Visit https://almagia.com/ to shop for Applanation Tonometer.