MORPHOLOGY AND FUNCTION OF THE CORNEAL ENDOTHELIUM AFTER LONG-TERM CONTACT-LENS WEAR

Purpose. To examine whether corneal hydration control is impaired in c orneas with endothelial morphologic changes (increased variation in ce ll size and cell angularity) due to long-term low gas-permeable contac t lens wear. Methods. Twenty-one long-term wearers of low gas-permeabl e contact lenses (mean age, 41 years +/- 8 SD) and 18 age-matched cont rols (mean age, 42 years +/- 8 SD) were studied. To assess endothelial morphology, endothelial photographs were taken, enlarged 400X, scanne d into a computer, and evaluated. Hydration control was assessed by a corneal stress test. Corneal swelling was induced by applying low gas- permeable soft contact lenses for 2 hours during eye closure. After th e lenses were removed, the rate of des welling was determined using op tic pachometry. Results. Morphologic analysis of the endothelial photo graphs showed a significant increase of polymegethism (P < 0.01) and p leomorphism (P < 0.01) in the group wearing contact lenses compared wi th the control group. The percentage of recovery of corneal thickness per hour (PRPH) from induced swelling proved to be significantly lower (P = 0.03) and the induced swelling proved to be significantly lower (P < 0.01) in the group wearing contact lenses than in the control gro up. Multiple regression analysis showed that the PRPH decreased as the morphologic alterations increased. However, this trend appeared not t o be significant at the 5% level. A significant relationship was found between morphologic parameters and induced swelling, indicating that induced swelling decreased as the morphologic alterations increased. C onclusions. The results of this study indicate that increased endothel ial polymegethism and pleomorphism may be accompanied by a decreased c orneal hydration control in people who wear contact lenses.