The effect of intraocular pressure on resistance to outflow.

As intraocular pressure is increased, facility of aqueous outflow decreases. For many years this fact was obscured by the often used procedure of experimental perfusion into the anterior chamber. Anterior chamber perfusion deepens the anterior chamber; retrodisplacement of the iris-lens diaphragm tenses the trabecular mesh with resulting facility increase and obscuration of the facility-reducing effect of pressure. The probable mechanism of facility reduction under experimental conditions is apposition of the inner wall of Schlemm's canal to the outer wall. Since facility of aqueous outflow is not constant at different intraocular pressures, application of poiseuille's law to the eye must be restricted to each pressure investigated.