Diseases affecting primarily the retinal arteries, capillaries and veins (or any combination of the three) can cause visual loss of varying degree. For evaluation of such problems a circulation study becomes necessary so that abnormalities of the blood flow patterns can be precisely identified. One such problem seen not infrequently is leakage form retina arterial aneurysm. See the accompanying photograph. Such patients are usually in the sixth or seventh decade of life when they experience an acute visual loss in one eye. Infiltration of the retina with red blood cells is the mechanism by which the vision is affected.