EFFECT OF FIBEROPTIC DIAMETER IN DIODE-LASER TRANSSCLERAL CYCLOPHOTOCOAGULATION IN HUMAN AUTOPSY EYES

Purpose: Contact fiberoptic laser transscleral cyclophotocoagulation ( TSCPC) is an aqueous inflow-reducing surgical treatment for glaucoma. One delivery device uses a 600-mu m diameter quartz glass fiberoptic w ith a hemispheric tip. A larger fiberoptic diameter would reduce fluen ce through conjunctiva and sclera. This study determined the relation of fiberoptic to ciliary body burn diameters after TSCPC with the IRIS Medical SLx diode laser system in human autopsy eyes. Materials and M ethods: Laser energy was applied with two models of delivery probe tha t were identical except for fiberoptic diameter (600 or 800 mu m) Both had hemispheric tips, each with the hemisphere radius equal to the ra dius of the fiberoptic. Six fresh human autopsy eyes (three pairs) wer e used, each receiving eight diode laser applications at 1.75 (2 eyes) or 2.0 (4 eyes) watts for 2.5 seconds-four applications per eye with the 600-mu m fiberoptic and four with the 800-mu m fiberoptic. Eyes we re fixed in 10% formalin then opened coronally at the equator. Inner s urface burn diameters were measured parallel and perpendicular to the limbus using calipers and an operating microscope at 10x magnification . Results: Ciliary body bums with the 600- and 800-mu m fiberoptic tip s had nearly the same average diameter, range of diameter, average are a, and range of areas. Conclusion: The 800-mu m fiber, which has a 78% larger cross-sectional area than a 600-mu m fiber, reduces fluence th rough ocular surface tissue during diode laser TSCPC, theoretically de creasing the risk of surface burns. In this study, the larger fiber gi ves essentially the same size ciliary body coagulation as obtained wit h the 600-mu m fiberoptic. This suggests that the larger fiberoptic, c ompared with the standard 600-mu m fiberoptic, will be more safe yet e qually effective for TSCPC.