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Cavanagh H. D., Li S., Yamamoto K., Ladage P. M., Petroll W. M., Jester J. V.
Background. To determine the effect(s) of open or closed eye and overnight contact lens (CTL) wear on rabbit corneal epithelial homeostasis.
Methods. Rabbits were fit unilaterally with CTLs of varying O2-transmission for up to 7 days with the contralateral eyes serving as controls or sutured closed. Surface cell apoptosis was measured in situ using Annexin-V binding, ethidium homodimer viability assay, and Bcl-2 or TUNEL immunocytochemical localization and Western blotting.
Results. 1) Open eye conditions (no lens) showed a central peak of non-viable corneal surface cells with 10.8±3.3 Bcl-2-negative and 3.5±1.7 TUNEL-positive cells/mm2; 2) closed eye conditions (no lens) significantly reduced the number of non-viable apoptotic surface cells (p<0.05); 3) all rigid gas permeable (RGP) or soft lens (SCTL) wear decreased corneal surface cell apoptosis with a significant decrease in Bcl-2-negative and TUNEL-positive surface cells (p<0.05).
Conclusions. 1) The O2-related Bcl-2 protein appears to play an important role in the regulation of apoptotic shedding in the normal rabbit corneal epithelium; all Bcl-2-positive cells are uniformly TUNEL-negative; 2) eyelid closure or the physical presence of the contact lens may protect against eyelid shear forces exerted by blinking; all lens wear decreases surface cell apoptosis associated with retained Bcl-2 expression.