Tonometer is an instrument which is used to measure intraocular pressure or tension. It is of various types like Gastric Tonometer, Applanation Tonometer, Indentation Tonometer, Rebound Tonometer, amongst others. An Applanation Tonometer is used for measuring the force which is needed for applanating or flattening an area of cornea. This type includes Dräger, Goldmann Tonometers, Halberg and MacKay-Marg. Rebound Tonometer is a compact, handheld and portable tonometer that has inbuilt digital readout and battery supply. Another important device is Non-Contact Tonometer (NCT), which can be used without any anesthesia as there is no need of making any contact with the eye and instrument.