Ar'cus Seni'lis

Ar'cus Seni'lis (Lat., 'the bow of old age'), a narrow white or yellowish band close to, but within the margin of the cornea (see EYE), caused by fatty degeneration of its tissue. It usually begins during middle life, first at the upper, then at the lower part of the cornea; before old age is reached, these two arcs have generally united at the sides to form a ring. It is frequently associated with Atheroma (see ARTERIES, Diseases of), but it is of no other practical importance.