Intraocular pressure is the pressure inside the eyeball which is determined by the production and the drainage of aqueous humor. The draingage is done mainly through the trabecular meshwork located in the anterior chamber angle, and into Schlemm's canal. it flows through 25 - 30 collector canals into the episcleral veins. The aqueous humor is produced by the ciliary body. Intraocular pressure is measured with a tonometer.
Intraocular pressure can rise when there is an increased pruduction or a bad outflow of aqueous humor due to an abnormal trabecular meshwork. This increase in the intraocular pressure is called ocular hypertension.