Anatomical and physiological studies on the aqueous sinus artery of the pigeon eye.

PURPOSE To test the hypothesis that ischemia of the Schlemm's canal endothelium is involved in the control of intraocular pressure (IOP). METHODS Experiments were conducted on pigeons. The course of the aqueous sinus and the aqueous sinus artery was determined by examining serial sections and the distribution of polymerized resin in the limbal region of the pigeon eye. Ischemia was produced by blocking two major arteries to the aqueous sinus artery and then determining the effect on the IOP. RESULTS The anatomy and course of the pigeon aqueous sinus and aqueous sinus artery indicated that they are homologous to the human Schlemm's canal and Schlemm's canal artery, respectively. When the arterial inflow to the aqueous sinus artery was blocked by laser treatment, injected resin was absent in the artery but a small amount invaded the aqueous sinus. Blockage of the two major arteries to the aqueous sinus artery did not alter the IOP. CONCLUSIONS The similarity of the pigeon aqueous sinus and aqueous sinus artery to the human Schlemm's canal and Schlemm's canal artery indicates that the pigeon eye can be used to study the relationship between ischemia of the endothelial meshwork cells and IOP. The lack of a change in IOP in pigeons after ischemia induction was probably the result of anastomotic arterial blood inflow to the aqueous sinus directly, and thus ischemia was not produced by blocking the two major arteries to the aqueous sinus artery.