Immunohistochemistry for the mitosis marker Ki-67 (green) with DAPI straining (blue) of all cell nuclei in rabbit corneas that had −9.0 D PRK for myopia with mitomycin C or vehicle balanced salt solution (BSS) application at the time of surgery and studied at 24 hours or 4 weeks later. Note there was marked cell proliferation (arrowheads) in the anterior stroma in the BSS group (C) at 24 hours after PRK, with some stromal cell mitosis continuing at 4 weeks after surgery. Markedly reduced proliferation of anterior stromal cells was found at 24 hours and at four weeks after PRK surgery in corneas treated with 0.02% mitomycin C for two minutes. If rabbit corneas were treated with 0.002% mitomycin C for 12 seconds, there were more anterior stromal cells undergoing mitosis at 24 hours and four weeks after PRK than with 0.02% mitomycin C, but less than in the BSS group. Mag. 200X. Reprinted with permission from Netto, et al. J. Ref. Surgery, 2006;22:562-574.