Which of the following condition is associated with Stockers' line?

A pterygium is a fleshy, triangular encroachment of a pinguecula onto the cornea, usually on the nasal side bilaterally. The cause of pterygium is believed to be related to ultraviolet and dust exposure. Clinically, a characteristic iron line (Stocker's line) may be seen at the advancing front of a pterygium. If the pterygium is enlarging and encroaches on the pupillary area, it should be removed surgically. Ref: Ophthalmology by Myron Yanoff, Jay S. Duker, James J. Augsburger, 2009, Page 364.