Mosa'a AL-Abdulmunem


Contact lenses induce physiological changes in the cornea. The contact lens acts as a barrier by impeding oxygen influx into the cornea and carbon dioxide efflux from the cornea. The effect of oxygen deprivation on corneal tissue at a cellular and subcellular level is not fully understood. The present study describes the corneal response to hypoxia in the absence of a contact lens. Contact lens wear was avoided since the lens may provoke trauma by nature of its physical presence and such changes could be confused with those caused by hypoxia alone. The cornea of one eye of a rabbit was exposed to humidified 100% nitrogen at 35 degrees C for four hours. The other eye, which acted as a control, was exposed to humidified air. Immediately following the exposure, the eyes were removed and prepared for transmission electron microscopy. Evaluation of the tissue showed a number of ultrastructural changes in the corneal epithelium. Fine intercellular edema was observed primarily among the basal cells. Mitochondria were often swollen or had disintegrated, especially in the deeper epithelial layers. Endoplasmic reticulum was dilated in several places. An increase in cell sloughing and a reduction in microvilli among surviving surface cells was also noted. Lactate accumulated in the epithelium and stroma because of oxygen deprivation. Membrane function may become defective secondarily to cellular energy depletion. We suggest that hypoxia-induced accumulation of lactate in the epithelium affects the ion pump (Na+,K+-ATPase) localized on the basolateral membranes of these cells, leading to intercellular edema. This interference with cellular membrane function leads to a defect in the mitochondria, which are the main source of energy in the cell. The observation that the epithelial intracellular changes occur predominantly in its deeper layers suggests that most metabolic activity takes place at this level. It is interesting that these, perhaps the earliest, ultrastructural chan


Year: 1992

Program Number: Poster 2

Author Affiliation: n/a

Co-Authors: B.Sc Optom, Nathan Efron, Ph.D. Cronly-Dillon, Jan Bergmanson

Co-Author Affiliation: n/a

Room: Great Hall