CHORIORETINAL VENOUS ANASTOMOSES - EFFECT OF DIFFERENT LASER METHODS AND ENERGY IN HUMAN EYES WITHOUT VEIN OCCLUSION

Background: This study was performed to determine the laser energy req uired to rupture both Bruch's membrane and retinal veins reliably in o rder to create a venous chorioretinal anastomosis. Methods: A histolog ical examination was conducted of argon green and YAG laser applicatio ns to the retina made prior to enucleation in eight eyes with large in traocular melanomas. Results: Argon laser application of 50 mu m in si ze and 0.1 s duration to intervascular areas of the retina will reliab ly rupture Bruch's membrane at a power level of at least 1.5 W. If the argon laser spot is placed overlying a retinal vein, a power level of up to 2.5-3.0 W will rupture Bruch's membrane in 60%, with only 34% o f the retinal veins showing evidence of rupture. The YAG laser with po wer levels of 3-4 mJ will reliably rupture the retinal vein in cases w here it has not previously been ruptured by the argon laser. Conclusio n: When attempting to create a chorioretinal venous anastomosis in an eye with a non-ischaemic central retinal vein occlusion, Bruch's membr ane should be ruptured first by placing the argon laser application at the side of the retinal vein before an attempt to rupture the retinal vein itself is made in case haemorrhage from the ruptured vein obscur es the view. A power level of at least 2.5 W should be used. If the ar gon laser is unsuccessful in rupturing the retinal vein, a YAG laser ( 3-4 mJ) is effective.