The drainage routes for aqueous humor in monkeys as revealed by scanning electron microscopy of corrosion casts.

The outflow routes for aqueous humor from the anterior chamber in cynomolgus monkeys were studied. The routes were filled with a mixture of Mercox CL2R and methyl methacrylate, 4:6, which had a low viscosity. Polymerization was delayed by cooling. Some experiments were performed after fixation with glutaraldehyde. Scanning electron microscopy was used to study the casts after dissolution of the tissue. The casts indicate inflow into the first intertrabecular space through a limited number of 10-100 microns openings. The first space is an irregular circular plexus. Subsequent uveal intertrabecular spaces also constitute complex channels. In the ciliary muscle the plastic entering from the uveal intertrabecular spaces could pass through narrow spaces into the supraciliary and suprachoroidal spaces. The intertrabecular spaces in the corneoscleral meshwork were thinner than those in the uveal meshwork. The outermost layer which tended to fill incompletely especially in fixed preparations communicated with the spaces of the juxtacanalicular tissue. In this tissue there was very limited filling even in unfixed preparations. On the casts of the canal of Schlemm there were remnants of communications with the juxtacanalicular tissue. These remnants indicated that only pores with diameters of 2-3 microns or more had been large enough to drain plastic into the canal. The collector channels formed a deep scleral plexus at many places. This plexus and direct collector channels drained into superior and inferior episcleral veins. Apparently the casting technique permitted visualization of most of the uveal and corneoscleral intertrabecular spaces and of preferential channels through the juxtacanalicular tissue and the inner wall of Schlemm's canal. The number of such channels was about 10-20/mm2 of inner wall.