THC:YAG laser sclerostomy with mitomycin subconjunctival injection in rabbits

We performed sclerostomy using THC:YAG laser (thulium, holmium, chromium doped YAG crystal) and subconjunctival injection of mitomycin soon after the filtering process in rabbits to observe the lowering effect of intraocular pressure(IOP) and filtering bleb formation. A 1-mm conjunctiva wound was made 12 mm away from the sclerostomy site to allow the entry of the optic probe for delivering energy. Forty-eight rabbits were divided into 3 groups. After sclerostomy, Group I received 0.2 ml normal saline subconjunctival injection and Group II and III received 0.2 ml mitomycin injection of 0.1 and 0.2 mg/ml respectively. One eye of each rabbit was randomly selected for the experiment while the fellow eye served as control. The bleb lasted 1.4 +/- 0.5 days (or 1 to 2 days) in Group I, 8.5 +/- 4.5 days (or 4 to 17 days) in Group II and 15.4 +/- 10.9 days (or 4 to 37 days) in Group III. The IOP lowering effect was significantly enhanced in Group III. The postoperative complication was minimal corneal punctate erosion in the mitomycin group, but all of them, however, resolved within one week. The results demonstrated that mitomycin is effective in prolonging the filtering effect produced by the THC:YAG laser.