It is generally believed that the normal corneal stroma has a tendency to swell in vivo and that this tendency is countered by some metabolic process in the epithelium, or endothelium, or both.1-10 One way that this process could act is through the removal of one or more of the constituents of the tissue fluid of the stroma across the cellular surface layers of the cornea. The active transport of water or of any single solute present to the extent of 5 millimoles per liter could be effective in overcoming the swelling force of the stroma.11 Harris12,13 has presented some evidence that water itself is actively moved, but others1,11,14 have suggested that the active transport out of the stroma of an ion such as Na might be a more efficient mechanism.
The isolated corneal preparation described in the previous paper has been used to study the
DONN A, MAURICE DM, MILLS NL. Studies on the Living Cornea In VitroII. The Active Transport of Sodium Across the Epithelium. AMA Arch Ophthalmol. 1959;62(5):748-757. doi:10.1001/archopht.1959.04220050010002