Structural analysis of potential barriers to bulk-flow exchanges between uvea and sclera in eyes of rabbits.

The uveal tract of rabbit eyes was examined using transmission electron microscopy of thin sections and freeze-fracture replicas. Emphasis was placed on the organization of pigmented and fibroblastic cells near the ora serrata and more generally in the lamina fusca, since these regions were previously found to restrict ingress of tracer molecules to the choroid in hamster eyes. There were significant differences between rabbit and hamster in the disposition of the pigmented cells and fibroblastic layers, the extent and patterns of tight junctions adjoining fibroblastic cells, and the presence of vesicles or fenestrations in the attenuated fibroblastic cell processes.