PURPOSE: To study the effect of long-term polymethyl methacrylate (PMMA) contact lens wear (CLW) on corneal endothelial morphology and corneal hydration control (CHC). METHODS: Sixteen long-term PMMA CL wearers (mean duration of wear 20.8 +/- 8.39 SD years; mean age 40.37 years +/- 10.47 SD) served as subjects and 14 age-matched, non-lens wearing subjects (mean age 41.29 years +/- 10.15 SD) served as controls. Corneal function was assessed by measuring the corneal thickness recovery rate (PRPH) after induced edema from a hypoxic stress load. Endothelial morphology was assessed by taking specular microscopy photographs, digitizing the images, and calculating the cell density, size, and coefficient of variation of cell size (CV). RESULTS: Morphologic analysis showed a significant decrease in mean endothelial cell density (2147 vs. 2865, p < 0.01), an increase in mean cell size (582 vs. 381, p = 0.001), and an increase in polymegethism (CV, 0.32 vs. 0.26, p < 0.01) for PMMA lens wearers compared to agematched controls. Corneal function as measured by PRPH was not significantly different for PMMA lens wearers compared to controls when taken as a whole. However, a subgroup of PMMA lens wearers (seven eyes, four subjects) did show a substantial reduction in PRPH. These subjects also showed a strong relation between reduced PRPH, morphology, and years of lens wear (r2 = 0.99). CONCLUSIONS: Longterm PMMA CLW leads to increased polymegethism in most, if not all, cases and results in a substantial decrease in corneal function in some cases.
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McMahon et al. (1996) studied this question.