The eye condition glaucoma, in which the pressure inside the eye is elevated, can be detected using an instrument called a tonometer. Anaesthetic drops are put into your eye, then the tonometer is pressed gently against the cornea, the transparent front part of the eye, and the force needed to flatten the cornea is measured. The test takes only a few seconds and is painless. A simpler form of tonometry (called non-contact tonometry) may be carried out during a routine eye test. This involves having a puff of air directed at your eye. The pressure in your eye is then calculated on the basis of your eye’s resistance to the puff of air.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.