Acquired diseases of the vitreous

Vitreous in health is a transparent avascular gel that functions to tamponade the retina and to serve as a media for the diffusion of soluble substances between the front and back of the eye. Primary vitreous originates from cellular contributions of mesoderm which forms the hyaloid vasculature and collagen produced by the retinal Mueller cells. The secondary vitreous surrounds the primary vitreous to form the bulk of the posterior segment. Primary acquired diseases of the secondary vitreous include vitreous degeneration, asteroid hyalosis, posterior vitreous detachment (PVD), syn-chisis scintillans, and vitreous cysts. Secondary vitreous involvement may be manifested by hemorrhage, inflammation, and membranogenesis. Vitreous degeneration is observed in three forms: condensation of vitreous collagen to form strands; liquefaction of the vitreous hydrogel; and trans-pupillary presentation of formed vitreous which may or may not contain pigmented cells. Vitreous hemorrhage may be the result of diverse local or systemic disease processes.