Fig. 29. Diagram illustrating the total transendothelial osmotic force due to Na+ activity, CL− activity, and imbibition pressure. Although the Na+ activity within the aqueous humor is greater than that within the stroma (142.9 vs. 134.4 mEq/L, P < 0.05.), using a reflection coefficient of 0.6, the calculated osmotic force due to Na+ is 98.5 mm Hg. Similar calculations for Cl− and imbibition pressure result in osmotic forces of −8.1 and −60 mm Hg, respectively. The sum of these forces results in a total osmotic force of +30.4 mm Hg, which ultimately results in deturgescence of the cornea. (From Stiemke MM, et al. Na+ activity in the aqueous humor and corneal stroma of the rabbit. J Exp Eye Res 55:425, 1992.)