Tonometry: What the Eye Pressure Test Measures

In the world of medical tests, tonometry becomes the centre of attention when it comes to measuring eye pressure. What exactly it measures and what is the use of measuring that will be discussed in the following article.

Tonometry is the practice of measuring the pressure within the eye, this pressure is called intraocular pressure (IOP). The intraocular pressure is created by continuous replenishing of fluids in the eye, measuring it tells optometrists if any chronic disease is present or is in developing stages. These diseases include glaucoma, cataracts and macular degeneration.

The test is can be done several ways, the following are the most commonly used methods.
Methods of Tonometry

#1 Goldman Applanation Tonometer

#2 Tono-Pen Handheld Electronic Tonometer

#3 Pneumotonometer Contact Device

#4 The Airpuff Noncontact Tonometer

#5 Tactile Finger Applanation

How it is done

Ophthalmologists prepare the patient for the test by placing numbing drops using topical anaesthetic such as tetracaine or proparacaine on the surface of the eyes, then they place the sensor of the tonometer against the eye’s surface. The reading is measured by the firmness of the tone on the surface of the eye. The only method where the eye’s surface is not touched by the sensor is that of air noncontact procedure.

Normal Pressures

So what are the normal values for IOP, it varies according to each individual. The average values for normal IOP is 10-21 (mm Hg) or millimeters of mercury level. The abnormal values for IOP range if the pressure is above 21 mm Hg.