Fig. 19. Diagram demonstrating the delicate balance between stromal swelling pressure, endothelial pump function, and intraocular pressure. Usually if endothelial cell pump function fails and IOP remains normal, slightly decreases, or increases, both stromal and epithelial edema occurs (center right). Only when IOP increases above the swelling pressure of the stroma and the endothelium functions normal do we see epithelial cell edema alone (center left) and only when IOP is zero and the endothelium functions abnormally do we see stromal edema alone (far right). (From Hatton MP, et al. Corneal edema in ocular hypotony. Exp Eye Res 78:549, 2004.)