Vascular occlusion is a blockage of a blood vessel, usually with a
clot. It differs from
thrombosis in that it can be used to describe any form of blockage, not just one formed by a clot. When it occurs in a major
vein, it can, in some cases, cause
deep vein thrombosis. The condition is also relatively common in the
retina, and can cause partial or total loss of vision. An occlusion can often be diagnosed using Doppler sonography (a form of
ultrasound).