There is a continuous process of development of new tonometer types following different measurement principles. The impedance measurement method, using the elasticity of the eyeball, allows tonometry even through the eyelid. Two new tonometers based on the impedance principle were investigated by clinical comparison measurements according to the international standard for human eye tonometers ( ISO 8612). The tested tonometers determine the intraocular pressure without topical anaesthesia. The different elastic properties of an individual eyelid and also the different elastic properties of the human eye due to a large variation in rigidity cause serious problems for these measurements. Statistical properties of the two investigated tonometers are presented and discussed. Statements and conclusions about the medical application of these measurement devices for ophthalmologists are made.