Definition of Intraocular pressure

Intraocular pressure: The pressure created by the continual renewal of fluids within the eye. The intraocular pressure is increased in glaucoma.

In acute angle-closure glaucoma, the intraocular pressure rises because the canal into which the fluid in the front part of the eye normally drains is suddenly blocked.

In chronic glaucoma, there is a gradual imbalance between the production and removal (resorption) of the fluid in the back part of the eye (with supply exceeding demand).