In a previous study1 we visualized by stereomicroradiographic techniques the filtration apparatus of the human eye. These techniques were valuable in confirming the existence of an open pathway between the anterior chamber and the episcleral venous system. The perfusion of these pathways with a radiopaque solution of thorium dioxide (Thorotrast) revealed both the intricate anastomosing network of vessels extending to the episclera and the elaborate vascular arcade in the peripheral cornea. However, this method did not show conclusively the openings into and out of Schlemm's canal, nor did it yield precise quantitative data on the number and size of these channels. It appeared that a different method would be required for such determinations.
In vascular research the technique of perfusion with graded spheres has been useful in determining the size of blood vessels.2 It seemed reasonable to suppose that this method would be applicable to the sizing of the
KARG SJ, GARRON LK, FEENEY ML, McEWEN WK. Perfusion of Human Eyes with Latex Microspheres. AMA Arch Ophthalmol. 1959;61(1):68-71. doi:10.1001/archopht.1959.00940090070009