Non-contact-based Tonometer and its Principles

Tonometry is the method that helps eye-care professionals in the measurement of pressure of their patients’ eyes. Technically, it is not pressure of eyes but of its fluids. Tonometry is quite a significant opthalmological test for the detection of glaucoma and the risk that it poses to patients. The method of almost every tonometer shows measurements in mm (millimetre) of mercury (Hg) and is denoted as “mm of Hg”.

A Non contact tonometer is not same as a Pneumatonometer. This type of tonometers can be better called an air-puff tonometers. Reichert Incorporation’s Bernard Grolman had invented tonometer that do not require any contact. The process requires fast air pulses for flattening of the cornea or applanation. Electro optical procedures are used for the detection of flattened cornea. The pressure of eyes of patients is verified by capturing the force of the jet of pressurised air when corneal flattening or applanation is in the process.

these devices were not considered to be reliable sources earlier. Instead, they were considered as devices for quick and simple measurement of the pressure inside the eyes be called a preparation for higher screening processes. It has now been established that a non contact tonometer of modern standards correlates quite nicely with measurements that are taken through the method of Goldmann tonometry. Tonometers that can work without any physical contact are very helpful devices as they capable of detecting ocular conditions in children and of those humans who are do not comply.

An Ocular Response Analyser or ORA is a type of non contact tonometer and functions depending upon the air-puff. It can be dispensed by using tropical anaesthesia. Additional information regarding biochemical properties of the cornea and other aspects of it are provided. A tonometer uses air-pulses to slight deform corneas into concave shape. Differences in ocular pressure during inward flattening and outward flattening of the cornea is then measured by tonometers. The values are used by tonometers for rectification of effects of the cornea on measurements.

Employment of Optical Coherence Tomography or OCT in non-contact-based tonometry is under development at present. Like other variations of tonometry, this method depends upon records of reaction of cornea during the application of force on it. For non-contact Optical Coherence Tonometry, applied force is measured by shock waves or an acoustic as aair in high pressure is released in form of jets. This technique also involves air at lower pressure that is forced through sealed chambers that occur around human eyes. Alteration in corneal curvature is measured by tonometers. It is utilised for the study of shift in the interface of cornea at the apices according to posterior interfaces of eyes such as retina, etc. Difference between the shift in those two interfaces provides an understanding of compression of the globe. The similarities between the shift in those two interfaces indicate globe retropulsion.

Presently, these devices have become reliable. The advancement witnessed this device has made it acceptable among optometrists and ophthalmologists. This is a very good process.

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