Differential permeance of retina and retinal pigment epithelium to water: implications for retinal adhesion.

Water movement from the vitreous to the choroid would tend to maintain retinal apposition, if the retina were less permeable than the retinal pigment epithelium (RPE). We used a rabbit model, to test the relative permeability of retina and RPE to tritiated water. The retina was found less permeable than the RPE. This result suggests the presence of a hydrostatic pressure gradient across the retina which could enhance apposition of retina to the RPE.