Treatment was usually completed in one or two sittings and included scatter (panretinal) photocoagulation extending to or beyond the vortex vein ampulae. The argon treatment technique specified 800 to 1,600, 500-micron scatter burns of 0.1 second duration and direct treatment of new vessels whether on or within one disc diameter of the optic disc (NVD) or outside this area (NVE). Focal treatment was also applied to microaneurysms or other lesions thought to be causing macular edema. Followup treatment was applied as needed at 4-month intervals. The xenon technique was similar, but scatter burns were fewer in number, generally of longer duration, and stronger, and direct treatment was applied only to NVE on the surface of the retina.