Abstract: A tonometer for measuring the Intra-ocular pressure of an eye includes an emitter for emitting a primary signal towards the cornea of the eye, a receiver for receiving the primary signal on being reflected from the cornea, and a monitoring device for monitoring the peak-to-peak amplitude of the reflected primary signal received by the receiver. The monitoring device is capable of taking and/or storing a measurement when the distance between the eye and the receiver is such that substantially the largest peak-to-peak amplitude of the primary reflected signal is received. The measurement is calibrated to provide the Intra-ocular pressure of the eye. A method of monitoring the Intra-ocular pressure of an eye is also disclosed.