This document discusses tonometry and intraocular pressure (IOP). It defines tonometry as the standard eye test used to determine fluid pressure inside the eye. IOP is the pressure of fluid inside the eye, which is normally between 10.5-20.5 mmHg. High IOP can lead to glaucoma, which damages the optic nerve. Factors like aqueous humor formation and drainage affect IOP. Tonometry methods include direct and indirect techniques, with indirect using contact applanation or non-contact methods to measure eye deformation from applied force.