Effects of eyelid closure and disposable and silicone hydrogel extended contact lens wear on rabbit corneal epithelial proliferation

PURPOSE. To examine the rabbit corneal epithelial cell proliferation rate after extended wear of disposable or silicone hydrogel contact lenses or prolonged eyelid closure. METHODS. One randomly chosen eye of 40 New Zealand White rabbits was assigned to silicone hydrogel contact lens wear (n = 15, SH), disposable hydrogel contact lens wear (n = 6, DH), eyelid suturing (n = 15, SUI), or no intervention (n = 4). Contralateral eyes served as the control. After 24 hours or 1 week of lens wear, 5-bromo-2-deoxyuridine (BrdU) was injected intravenously to label dividing corneal epithelial cells, and animals were killed 24 hours after injection. Corneas were stained with monoclonal anti-BrdU antibody and FITC-conjugated secondary antibody. A series of continuous digital images of the wholemounted epithelium were collected from the superior to inferior limbus, and the number of BrdU-labeled cell pairs was counted. RESULTS. SH, DH, and SUT caused a significant decrease in BrdU-labeled pairs of cells over the entire corneal epithelium at day 2 compared with the number in contralateral control eyes (P < 0.001). One week of SUT or SH caused a significant increase centrally in BrdU-labeled cells (P < 0.01). BrdU labeling at the limbus in all groups was not significantly different from the control. Unexpectedly, the proliferation rate of the control corneas was also significantly affected by contralateral lens wear and suturing. CONCLUSIONS. Short-term overnight SH, DH, and SUT all significantly suppressed the cell proliferation rate in the rabbit corneal epithelium. However, adaptation, with central hyperproliferation of cells, appeared to occur at 8 days. The effects of lens wear and eyelid suturing on the cell proliferation rate in contralateral control eyes suggests a central mechanism that regulates corneal epithelial proliferation.