[Retinal vascular closure using laser photocoagulation].

The aim of this experimental work was to produce a vascular occlusion of the retina by laser photocoagulation. Three types of lasers were used: argon green (514 nm), yellow laser (574 nm) and double frequency Neodymium YAG (514 nm) (DF-Nd: YAG) (532 nm). Pigmented retinas from 18 rabbits were photocoagulated using the three mirror technique under general anaesthesia. A fluorescenin angiogram of the retina was done after the photocoagulation to verify vessel occlusion. The rabbits were sacrificed at one day, one week and three weeks after photocoagulation for histology examinations. In most cases, laser photocoagulation did not cause vessel constriction. The angiograms showed that flow was slower but not interrupted. Yellow and DF-Nd: YAG lasers were more effective in creating vascular occlusions. The three lasers caused similar histological lesions which varied only in their extension to the different layers of the retina. The endothelium was destroyed and red cells aggregated in the vessel lumen. These findings suggest that yellow and DF-Nd: YAG laser should be used in all situations requiring coagulation of a vessel in the retina.