Bipolar cautery and internal thermal sclerostomy in a rabbit model

Internal thermal sclerostomy (ITS) was performed unilaterally in 35 adult New Zealand rabbits using a pinpoint bipolar cautery probe and radio-frequency power supply, with the nonoperated eyes serving as controls. Standard trabeculectomy using a limbal-based flap was also performed on 10 additional rabbits, and served as a second bench mark for comparison with the ITS technique. Intraocular pressure (IOP) was measured in all eyes preoperatively and on postoperative days 2, 4, 6, and 8. A significant (P = .005) difference between the reduction in IOP in the ITS eyes and in the control eyes was found up to postoperative day 8; on that day the reduction in IOP was 5.2 mm Hg. IOP in the eyes undergoing standard trabeculectomy was significantly (P = .05) reduced up to postoperative day 2, and gradually decreased, to 2.5 mm Hg, on postoperative day 8. The greatest reduction in IOP (2.9 mm Hg) for these eyes also occurred on postoperative day 2. Complications of ITS included iris burn (23%), peripheral corneal edema (17%), and iritis (9%). No ruptured blebs, flat anterior chambers, hyphemas, or lens damage occurred. The potential advantages of the ITS procedure using the bipolar cautery probe include a decreased risk of cataract formation because of the curved probe design. The procedure is also technically simple to perform and requires only inexpensive and readily-available equipment.