Asteroid Hyalosis
Asteroid hyaloids or calcium soaps in the vitreous are easy to detect in B-scan ultrasonography.
The reflections remain long after the sensitivity is reduced and other ocular structures disappear due to their acoustical density.
Asteroid hyalosis is a vitreal condition in which calcium soaps accumulate and disperse throughout the vitreous. It appears similar to vitreal hemorrhage, but can be differentiated from the latter by its acoustical density. Because calcium is an excellent reflector of sound, asteroid hyalosis particles disappear late as the sensitivity is decreased and well after blood disappears, as blood is less acoustically dense than is calcium. Keep in mind that bone, calcium and metal reflect sound best and hence persist at low sensitivity settings.