Wilson G
Vision Science Research Center, School of Optometry, University of Alabama at Birmingham 35294-4390, USA.
Cornea. 1996 May;15(3):240-4. doi: 10.1097/00003226-199605000-00003.
It has been stated that in dry eye hyperosmolality damages the epithelium of the ocular surface by increasing the rate at which cells are shed. To test this hypothesis, paired excised rabbit corneas were superfused with balanced salt solutions in which all conditions were held constant except the osmolality in contact with the epithelium. For a period of 400 min the epithelium of one of the corneas was exposed to one of seven test osmolalities (200-425 mOsm/kg), whereas the other cornea was used as a control (305 mOsm/kg). The number of cells shed from each corneal surface was counted, and thickness changes in the epithelium and stroma were measured. Only hypoosmotic solutions of 260 mOsm/kg or less increased the number of cells shed relative to the control. None of the hyperosmotic solutions significantly increased the shedding rate. There was no significant change in the thickness of the epithelium, whereas the stroma swelled in hypoosmotic solutions and thinned in hyperosmotic solutions. It is concluded that hyperosmolality in the range encountered in dry eyes is not sufficient in itself to increase the shedding rate.
