The filtration characteristics of the aqueous outflow system

To determine the filtration characteristics of the aqueous outflow system, microspheres (0·18 μm–1·1 μm) were perfused through enucleated human and bovine eyes. The microspheres were smaller than morphologically determined flow dimensions, and yet a significant fraction of all sizes of microspheres were captured. The bovine (calf) aqueous outflow system was found to be a far more efficient filter than was the human outflow system. Combining the experimental results with morphological observations and theoretical calculations leads to the conclusion that ‘sticky wall’ interactions are responsible for much of the microsphere capture, and that the site of filtration may be distinct from the site of flow resistance. Consequently, the dimension of the sites generating flow resistance cannot be determined from filtration studies.