Tonopen and Glaucoma

Glaucoma is a group of diseases of the eye characterized by increased intraocular pressure, resulting in pathological changes in the optic disc.

A tonopen is a tool used to check the pressure exerted by the fluid inside a pet's eyes. This is done to make sure the eyes and optic nerves are healthy. The normal eye is filled with aqueous humor (fluid) that is produced behind the iris. This fluid flows through the pupil and drains from the eye. The fluid is produced and drained at approximately the same rate resulting in a stable pressure within the eye.

Glaucoma is a consequence of a blockage of the outflow and a subsequent buildup of pressure within the eye.

High pressure compresses the optic nerve and results in blindness.