Degenerative conditions of the vitreous.

Abstract

This chapter discusses three conditions, asteroid hyalosis, synchysis scintillans, and amyloidosis of the vitreous, commonly referred to as vitreous degenerations. The term vitreous degeneration is imprecise since it implies a primary process in the vitreous gel itself. The vitreous gel is composed of a liquid and a solid phase. The solid components of the vitreous constitute only 1% of its weight and consist of collagen fibrils, peripheral cells, and small amounts of other proteins. The liquid phase (99%) is essentially water with the addition of hyaluronic acid, inorganic salts, ascorbic acid, and sugars. This type of configuration suggests that the major function of the vitreous is to modulate the passage of metabolites and other biochemical substances to and from adjacent tissues. Most likely, the only primary degeneration of the vitreous body itself is syneresis and vitreous detachment. Most vitreous degenerations are secondary to primary retinal degenerations and are referred to as hyaloideoretinopathies. The vitreous gel may entrap material from surrounding tissues when they are diseased. Plasma proteins and inflammatory cells may enter the vitreous when the adjacent structures are inflamed.