Branch artery occlusion. (A) Occlusion of superior nasal branch of central retinal artery at junction of branch of central retinal vein. Artery is dark and portion of artery on optic disk cannot be discerned. Sector of retina not perfused has ground-glass appearance. Early laminar flow can be can be seen in some branches of veins. Blood in upper branch of inferior nasal vein contains fluorescein only on side of vein adjacent to normally perfused retina. (B) Previously blocked vessel, seen several days later, is open and carrying blood. Background fluorescence appearance appears normal and retina does not have ground-glass appearance. Compare portion of artery crossing optic nerve with that in part A taken at a slightly later phase of angiogram.