Tonometry is a medical test used to measure the pressure inside the eye, known as intraocular pressure (IOP). This measurement is important for diagnosing and monitoring conditions like glaucoma, which can lead to vision loss if not treated. The most common method of tonometry is the applanation tonometry, where a small probe gently flattens a part of the cornea to gauge pressure. Other methods include non-contact tonometry, which uses a puff of air, and indentation tonometry, which involves pressing a small device against the eye. Regular tonometry tests help maintain eye health.