There are various methods to measure intraocular pressure. Goldman Applanation Tonometry is still frequently used. However, it must be done in an office where such a device is available and it must be performed under local anaesthesia. Although painless, it is a tedious procedure for the patient.
Airpuff tonometry, on the other hand, does not require the eye to be anaesthetized but it is expensive and unpleasant for the patients. The measurement results on both types of tonometers are strongly depending on corneal thickness, a problem which is also related to other so called rebound tonometers.

The IOPEN Tonometer has been developed for portable, anaesthesia-free cost effective screening of intraocular pressure. Its unique way of measuring the viscoelastic properties of the eye leads to results which are independent from corneal thickness.