[Electron-microscopic and biochemical characteristics of pterygia (author's transl)]

Histologically, pterygium is characterized, apart from the presence of typical collagen fibers, by the appearance of fibres which take up elastic stain but differ from normal elastic tissue, as was confirmed by electron-microscopic investigations. Thus, "elastoid degeneration" of collagen is characterized by the loss of the characteristic periodic fibril structure and by the appearance of coiled and knotty fibres. Collagen types in pterygium were identified biochemically for the first time. The main bulk of collagenous tissue consists of 80-90% Type I collagen, while only 10-20% Type III collagen was detected. Type IV collagen (basal membrane collagen) was present in low amounts. Digestion with elastase resulted in 20% solubilization of pterygium, while bacterial collagenase digested up to 40% of the tissue dry weight.