Important details of the aqueous humor outflow system, previously inaccessible to study in the intact eye, can now be observed by radiography. The technique is based on radiographs of the angle of the anterior chamber taken after replacing aqueous humor with water-soluble radiopaque material.
Biomicroscopy is limited as a tool for the study of the crucial details of the mechanism of aqueous humor outflow. A gonioscopic view of the angle of the anterior chamber reveals the trabecular meshwork, which is only the beginning of the outflow system. And with the slit lamp the aqueous veins and laminary veins, beneath the conjunctiva, can be identified and traced in a retrograde direction to the point where they disappear into the sclera. The system of minute drainage channels, between the inner trabecular and outer episcleral surfaces, within the optically opaque sclera, and beyond the limits of biomicroscopy, has been studied by two major
COHAN BE. Radiography of Aqueous Humor Outflow. AMA Arch Ophthalmol. 1958;60(1):110-115. doi:10.1001/archopht.1958.00940080124015