Morphology and function of the corneal endothelium after long-term contact lens wear

To examine whether corneal hydration control is impaired in corneas with endothelial morphologic changes (increased variation in cell size and cell angularity) due to long-term low gas-permeable contact lens wear.

Twenty-one long-term wearers of low gas-permeable contact lenses (mean age, 41 years +/- 8 SD) and 18 age-matched controls (mean age, 42 years +/- 8 SD) were studied. To assess endothelial morphology, endothelial photographs were taken, enlarged 400X, scanned 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 the lenses were removed, the rate of deswelling was determined using optic pachometry.

Morphologic analysis of the endothelial photographs showed a significant increase of polymegethism (P < 0.01) and pleomorphism (P < 0.01) in the group wearing contact lenses compared with 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 group. Multiple regression analysis showed that the PRPH decreased as the morphologic alterations increased. However, this trend appeared not to 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.

The results of this study indicate that increased endothelial polymegethism and pleomorphism may be accompanied by a decreased corneal hydration control in people who wear contact lenses.