TOPICAL MINOXIDIL FOR GLAUCOMA FILTRATION SURGERY IN THE RABBIT

Studies evaluated the effect of topical minoxidil on the proliferation of limbal fibroblasts in rabbits following filtration surgery. New Ze aland white rabbits underwent unguarded trabeculectomies in a masked, randomized, paired-design prospective study. Rabbits were treated topi cally every 3 hr around the clock for 1, 2 or 4 days post-operatively, with one drop of a 50-mu l solution containing either 20, 40 or 120 m M minoxidil or the vehicle alone. Another group of animals continued t o receive 120 mM minoxidil topically every 8 hr for up to 10 days. Int raocular pressure (IOP), bleb appearance, signs of ocular toxicity and anterior chamber reaction were monitored. Animals were killed and tis sues immediately surrounding the trabeculectomy ostium were removed an d processed for vimentin detection by immunohistochemistry. Minoxidil, in 20 and 40 mM concentrations, did not induce a significant IOP redu ction, nor prolonged bleb survival at any time point, and the changes in fibroblast counts between treated and control eyes were insignifica nt (P > 0.05). Fibroblast counts in the 120 mM minoxidil-treated eyes were significantly reduced by 42.6% within 24 hr compared to control ( P < 0.001). This inhibitory effect remained for at least 2 days after surgery (P < 0.05), the critical period for scar formation. The blebs in this group remained consistently higher than in any other group, an d some blebs survived for up to 8 days after surgery. IOP remained bel ow preoperative level for at least 6 days in 50% of the eyes treated w ith 120 mM minoxidil (P < 0.05). There was no significant reduction in fibroblast counts after 4 days from surgery (P > 0.05). For the contr ol eyes, all blebs were 'flat' to masked grading, and IOP returned to preoperative levels by post-operative day 5. No adverse reactions were noticed in any eye. In summary, minoxidil can delay surgical wound he aling. In concentration of 120 mM, minoxidil increased the longevity o f the bleb and the duration of postoperative ocular hypotension.