Traditionally, intraocular pressure (IOP) has been measured by applanation of the cornea, using a topical anaesthetic, or by non-contact tonometry (NCT), using a puff of air on to the cornea. 

Recently a new type of contact tonometer has been made available: the iCARE is a rebound tonometer that does not require the use of an anaesthetic. Rebound or dynamic tonometry is based on making a moving object collide with the eye, and the motion parameters of the object are monitored following contact. 

Measuring the IOP in a domiciliary environment can be difficult; it was therefore decided to compare this new instrument with the two tonometers most commonly used by domiciliary companies – the Tonopen and the Pulsair. These instruments are used since they allow IOP measurements to be obtained in an objective manner, as does the iCARE. Instruments such as the Perkins, which require a subjective assessment, are less common in domiciliary practice.