Tonometer (təˈnɒmɪtə) is a medical device used to measure the pressure within the eyeball, commonly known as intraocular pressure or IOP. The spelling of the word "tonometer" can be explained using the International Phonetic Alphabet (IPA) transcription. The prefix "t(o)no-" comes from the Greek word tonos, meaning tension or tone. The suffix "-meter" is derived from the Greek word metron, which means measure. Thus, tonometer is a device used for measuring the tension or tone of the eye, aiding in the detection and management of glaucoma.
A tonometer is a medical instrument specifically designed for measuring the intraocular pressure (IOP), which is the pressure within the eyeball. It is primarily used in ophthalmology to diagnose and monitor conditions such as glaucoma, wherein an elevated IOP can lead to damage of the optic nerve and potential loss of vision.
There are different types of tonometers, but the most common one is called the applanation tonometer. This instrument typically consists of a small probe that gently touches the cornea (the transparent front part of the eye) to measure the pressure accurately. By applying force to the cornea, it causes a slight flattening or indentation, which is measured to determine the IOP. Other less common tonometers use an air puff or indentation of the cornea to determine the pressure.
The tonometer's measurements are typically expressed in millimeters of mercury (mmHg), and the normal range for IOP is usually between 10 and 21 mmHg. An abnormally high or low IOP can be indicative of various eye conditions and can help ophthalmologists make accurate diagnoses and determine appropriate treatment plans.
In conclusion, a tonometer is a specialized medical instrument used to measure the intraocular pressure, aiding in the diagnosis and management of eye disorders such as glaucoma.
1. An instrument for determining intraocular tension. 2. An instrument for determining the degree of blood-pressure; see sphygmomanometer and Bishop, Gaertner, Janeway, Riva-Rocci, and Rogers.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
The word "tonometer" has its roots in Greek. It is derived from two Greek roots: "tonos" meaning "tension" or "pressure", and "metron" meaning "measure". Thus, the meaning of the word "tonometer" is a device used to measure or indicate the pressure or tension. In the context of medical science, a tonometer is specifically used to measure the pressure within the eye.