It’s used to measure intraocular pressure (IOP).
There are several types of tonometers, including:
1. Indentation tonometer: Measures how much the cornea indents with a known weight.
2. Applanation tonometer: These measure the force required to flatten a constant area of the cornea. The Goldmann applanation tonometer is the most widely used type.
3. Non-contact tonometer (Air puff tonometer): Uses a puff of air to measure IOP without touching the eye.