1. An instrument that measures pressure in a body part; such as, the blood vessels, or the eyeball as a test for glaucoma.
2. An electronic device that measures hydrostatic pressure within the eye.

When it is put into position, a tiny movable plate is pressed against the eye, flattening a circular section of the cornea; a current is then sent through a small electromagnet, of such value that it will just pull the plate away from the eye.

The value of the current is proportional to eye pressure and a measurement can be made in about one second.

It is usually used in the diagnosis of glaucoma.