Optical Detectors are used for the detection of optical radiation that is usually accomplished by converting the optical energy into an electrical signal. It include photon detectors, in which one photon of light energy releases one electron that is detected in the electronic circuitry and thermal detectors, in which the optical energy is converted into heat, which then generates an electrical signal.

Optical non-contact tonometer is an instrument used to determine the intraocular pressure (IOP), the fluid pressure inside the eye. It is used in the evaluation of ocular conditions such as glaucoma as well as conditions such as phthisis bulbi, and iritis. It has the obvious advantage of not requiring contact with cornea. This minimizes the potential for corneal compromise, negates the need for anaesthesia, and in many cases is preferred by the patient. The basic operation relies upon the applanation of an area of cornea by a jet of air, which usually switched on and off at a point dictated by the quality of image of reflected light from a source on the tonometer.