Spontaneous and pharmacologically-modulated wound healing after Nd:YAG laser sclerostomy ab interno in rabbits

The course of tissue repair evoked by Nd:YAG laser sclerostomy ab interno and the effect of mitomycin-C on same were investigated ultrastructurally in 15 rabbits. In ten of them, the dynamics of the spontaneous postoperative healing response (i.e. in the absence of medication) was analyzed at two-day intervals by light- and electron microscopy. In two, fibroblast activity was assessed autoradiographically. In the last three rabbits, the sclerostomy site was exposed transconjunctivally to mitomycin-C (0.5 mg/ml; 5 minutes) before surgery, and morphological analysis was done on postoperative days 6 and 12.

In the spontaneously healing group, blebs disappeared within five days of surgery. This corresponded to a massive invasion of macrophages and fibroblasts from the episclera and iris root. The sheath of coagulated tissue around the fistula appeared to act as a barrier to cell migration from the sclera itself at this stage. By days 8 to 12, the canal had become occluded by a network of cells and capillaries, and collagen fibrils in the coagulation sheath had undergone repolymerization. In the mitomycin-C group, large filtering blebs and patent, cell-free fistulas were observed over the entire period. Although applied transconjunctivally, the drug penetrated the whole scleral depth, as the iris root and ciliary body cell reaction was inhibited. Repolymerization of heat-damaged collagen was also hindered. The overall findings provide information on the sequence of repair events following laser sclerostomy. Local, non-invasive application of mitomycin-C delays the onset of this process, not only by inhibition of cell proliferation but also by suppressing the collagen recovery.