Arcus Senilis

ARCUS SENILIS (gerontoxon), senile arc, an opacity in an otherwise normal cornea in the form of a narrow crescent or ring on its periphery. The outer border of A. s. is sharply defined and separated from the edge of the cornea by a narrow transparent gap; the inner border is indistinct and gradually merges with the transparent part of the cornea. Initially, arcs appear at the upper and lower edges of the cornea and later, merging with each other, form a closed ring. Usually A. s. appears in old age; occasionally it is also found in young people. Patho-anatomically, in the thickness of the cornea, deposits of the smallest fat droplets (Virchow), hyaline substance masses, and even lime deposits (Fuchs) were found. In recent times, the cause of fat deposition and the occurrence of A. s. is sought in an increased cholesterol content in the blood serum, which is proven experimentally in rabbits (Anichkov N. N., Verse, Rohrschneider) and clinically in patients. Sometimes the cornea may become so thin at the site of A. s. that grooved depressions form and marginal protrusions and even ruptures of the cornea may develop.