Tonometer is a measuring instrument which is used at the time of diagnosis to measure the pressure inside the eye, meaning, the intraocular pressure (IOP). This measuring test, apart from part of a routine eye checkup, is most important for any medical practitioner to determine whether or not a patient is at a risk of glaucoma. Any individual’s intraocular pressure (IOP) must generally be 15, and readings in the region of 21 or 22 determine an increased probability that the patient will go on and develop glaucoma. Glaucoma is a severe eye disease wherein there exists an elevated fluid pressure within the eye, and this increased pressure is damaging to the optic nerve. According to the tonometer research analysis, glaucoma is more probable in people who are above 60 years of age and is one of the leading reasons for blindness. Most of the tonometers are calibrated to measure pressure in millimeters of mercury (mmHg).

Tonometry checks IOP by determining the resistance of the cornea to pressure (indentation). Anesthetic eye drops to numb the surface of the eye before any of the following methods:

Electronic indentation tonometry – One of the most widely used tonometer to check for increased IOP. Even though the results are quite accurate, electronic tonometry results might differ to other tonometry methods. This method involves placing of a rounded tip of a tool which looks like a pen directly on the cornea.

Applanation (Goldmann) tonometry – This variant of tonometry makes use of a tiny poke onto a gently flatten part of the cornea to measure the pressure of the eye with the help of a microscope called a slit lamp. The pressure is determined by the amount of force required to flatten the cornea.

Noncontact tonometry (pneumotonometry) – This method does not come in contact with the eye, instead uses a puff of air to flatten the cornea. This might not be the most effective way to measure the intraocular pressure, but is one of the easiest ways to test children and does not involve the use of numbing eye drops.