Flow of water between aqueous and vitreous compartments in the rabbit eye

When fluoresceinated dextran (FD) is injected into the vitreous body of the rabbit, it diffuses out of the eye through the anterior chamber so that the ratio of its concentration in the aqueous to that in the vitreous humor remains constant. The rate of loss of the substance from the eye suggests that the vitreous body is stagnant. After penetrating the vitreous body with a 25-gauge needle through the sclera, the FD fluorescence in the aqueous humor is reduced by a factor of three times on the average. This appears to be because the loss of fluid out of the scleral hole sets up a backward seepage of fluid through the anterior vitreous body, which opposes the diffusion of dextran into the anterior chamber. In contrast, making a needle hole has little effect on the level of sulforhodamine B, a more rapidly diffusing molecule, when it has been injected into the vitreous body, and none at all when it has been introduced into the cornea. The changes in the flow across the aqueous-vitreous interface, as well as the changes in aqueous outflow after an experimental intervention to the eye, may be estimated from a comparison of the changes in fluorescence in the anterior chamber of large and small molecular weight compounds injected into the vitreous body.