Proliferation rate of rabbit corneal epithelium during overnight rigid contact lens wear

PURPOSE. To examine cell proliferation of the normal corneal epithelium and during extended rigid gas-permeable (RGP) lens wear. METHODS. Twenty-three New Zealand White rabbits were fitted unilaterally wi th either a low oxygen transmissible (Dk/t) or hyper-Dk/t RGP lens, with th e other eve serving as a control. The rabbits were injected with 5-bromo-2- deoxyuridine (BrdU) 24-hours later and killed at three time points: 1, 3, a nd 7 days after injection. Corneas were processed for immunocytochemistry, and sequential digital images were taken from the superior limbus to the ce ntral epithelium with an epifluorescence microscope. The total number of Br dU-Iabeled cell pairs was quantified. RESULTS. The limbus in normal corneas was significantly less Populated with BrdU-labeled cells than the central and peripheral epithelium (P < 0.05). The peripheral epithelium adjacent to the limbus was marked by a peak of la beled cells (P < 0.05). Both types of RGP lenses produced an increase in Br dU labeling in the limbus and a dramatic decrease in the central epithelium (80% for low Dk/t, 37% for hyper Dk/t). At day 3 and 7 after BrdU injectio n, the low-Dk/t lens continued to show decreased BrdU labeling centrally, w hereas the limbus remained increased. Hyper-Dk/t lens wear however, showed persistent limbal elevation but equivalent numbers of BrdU-labeled cells ce ntrally at days 3 and 7, compared with control corneas. Keratocytes unexpec tedly showed BrdU labeling during RGP lens wear. CONCLUSIONS. Limbus, peripheral, and central epithelium were characterized by different proliferation rates in the normal rabbit cornea. RGP lens wear significantly altered the homeostatic proliferation pattern of the epithel ium with the low-Dk/t lens having the most dramatic effect. RGP contact len s wear appears to Stimulate proliferation of keratocytes.