Ultrastructural and histochemical studies of conjunctival concretions.

Ultrastructural and histochemical studies were performed on conjunctival concretions (yellow spots in the tarsal conjunctiva) from two patients who had associated atopic keratoconjunctivitis and posttrachomatous degeneration. By electron microscopy, these concretions were composed of finely granular material and membranous debris accumulating in the conjunctival subepithelium. Histochemically, concretions stained strongly positive for phospholipid and elastin, weakly positive for neutral polysaccharides and lipid, and were negative for amyloid, collagen, glycogen, iron, mucopolysaccharides, RNA, and DNA. In view of the absence of both calcium and phosphate in the accumulated material, the use of the term "lithiasis" is misleading and should be avoided. These findings support a hypothesis that concretions that follow chronic conjunctivitis represent products of cellular degeneration.