[Retinal photocoagulation in hemorrhagic retinal branch vein thrombosis. A new treatment technique].

In branch vein occlusions involving the macula, the loss of macular function cannot be due to hypoperfusion of the involved capillaries, because if this were so the uninvolved part of the macula would presumably be unimpaired. The impairment of the macula is explained as follows. Congestion of the blood caused by the thrombosis means that the capillaries are exposed to high blood pressure. In the border zone of the thrombotic area capillaries that are normally drained are exposed to capillary hypertension. For this reason, the border zone of a retinal thrombosis is also affected. The perifoveal capillary network is usually in this border zone. We treated branch vein occlusions by perimacular photocoagulations on the blood in the inner retinal layer within the zone of the thrombosis. Our explanation for the gain in visual acuity following this procedure is that we occlude the retinal capillaries that are, passing on the high pressure into the perifoveal capillaries. Our proposed photocoagulation procedure is restricted to cases in which hemorrhage has led to enough blood in the inner retinal layer to coagulate. The destruction of the nerve fiber layer by this kind of photocoagulation has to be taken into account. The possible gain of visual acuity has to be balanced against the loss of function caused by destruction of parts of the nerve fiber layer.