A tonometer is usually composed of a corneal shape change generator, a corneal deformation measuring system or contact corneal device and a pressure change sensor. Used to measure intraocular pressure. Common products are tonometer, non-contact tonometer, handheld tonometer, handheld applanation tonometer, applanation tonometer, contact piezoelectric tonometer, rebound tonometer, Indentation tonometer, etc. It can assist in the diagnosis of cataracts, glaucoma and other eye diseases. The non-contact tonometer is commonly used now, which has the advantages of simple operation and rapid measurement.