A comparison of three different setting protocols of transscleral diode laser cyclophotocoagulation in chronic canine glaucoma

Abstract

Transscleral diode laser cyclophotocoagulation is the method to lower the intraocular pressure by causing coagulative necrosis of ciliary epithelium, resulting in a decrease of aqueous humor production. This study was to compare clinical outcome and pathological changes of ciliary body, using three different setting protocols in chronic canine glaucoma. Protocol I 1500:1500 (power:duration), 40 spots, 270 degrees around the globe at 3, 4 and 5 mm posterior to the limbus, Protocol II 1500:1500 (power:duration), 80 spots, at the area as described in protocol I, and Protocol III 1000:2500 (power:duration), 80 spots, 360 degrees circumferential at 3 and 4 mm behind the limbus. Rate of success in reducing intraocular pressure was 60%, 90% and 100% in protocols I, II and III, respectively. Number of laser spots and total energy delivery per eye were highly correlated to the success. Reduction of intraocular pressure, topical hypotensive medication application and axial globe length were relatively comparable among the three protocols. Ulcerative keratitis was the main complication in all protocols while aqueous flare was the major cause of uncontrollable intraocular pressure, leading to enucleation in protocols I and II. Coagulative necrosis and ciliary tissue separation were found in all protocols with different extent, while pars plana was intact.