Differential swelling in compartments of the corneal stroma.

When a hypotonic solution is applied to the corneal surface the stroma swells. This well-known osmotic response masks a surprising hydration change in the posterior stroma. This was studied by measuring thickness changes in the anterior, middle, and posterior stroma of the rabbit cornea. Measurements were made continuously for 1 hour following osmotic perturbation of the epithelial surface. The data revealed that following a hypotonic shift on the epithelial surface, the posterior stroma thinned briefly. This unexpected effect is predicted satisfactorily by Klyce and Russell's mathematical model. The method of measuring fluid flow between stromal compartments will allow further development of the model in describing the dynamics of stromal hydration.