MINOXIDIL-INDUCED ALTERATION OF CORNEAL TOPOGRAPHY AFTER RADIAL KERATOTOMY

Purpose: To determine the antiproliferative effect of minoxidil on hum an corneal epithelium (hCE) proliferation in vitro and to assess wheth er topical minoxidil can significantly alter corneal topography after radial kerototomy (RK) by inhibiting myofibroblast activity in the ker atotomy wound. Setting: Corneal Research Laboratory, University of Chi cago, Illnois, USA. Methods: In the in vitro evaluation, proliferation hCE was exposed to minoxidil (0.1 to 2.0 mM) for 96 hours to determin e the minimum inhibitory dose. Human corneal epithelium cell prolifera tion was assessed by the incorporation of bromodeoxyuridine (BRDU) int o DNA. In the in vivo analysis, eight New Zealand albino rabbits had a n eight-incision bidirectional RK on one eye and were divided in to tw o groups. The control eyes (n = 3) received tobramycin and dexamethaso ne (TobraDex(R)), ciprofloxacin hydrochloride (Ciloxan(R)), and balanc ed salt solution (BSS(R)) drops four times a day for three weeks, whil e the treatment eyes (n = 5) received TobraDex, Ciloxan, and minoxidil 1.0 mM drops four times daily for 3 weeks. The net change in corneal curvature at 3 weeks was analyzed with corneal topography. Myofibrobla st activity in the keratotomy wound was assessed using alpha smooth mu scle actin staining techniques. Results: At concentration of 1.0 mM an d above, minoxidil caused a statistically significant, dose-dependent reduction in hCE cellular proliferation ranging from 29 to 44% (P < .0 5). Minoxidil (1.0 mM) caused a statistically significant central corn eal flattening effect of 4.66 diopters (D) after RK in the treatment e yes compared with 1.11 D in the control eyes (P = .05). Histologically , minoxidil-treated keratotomy wounds lacked cells with contractile el ements consistent with myofibroblast differentiation. Corneal epitheli al wound healing was similar in both groups. Conclusion: At the approp riate dose, topical minoxidil may be a useful adjunctive treatment tha t can reduce the number of undercorrections after mini-RK without appa rent toxicity to the corneal epithelium.