The "O" sign--clue to a lost lens.

The authors describe two patients who lost a hard contact lens beneath the upper lid. After a year they presented with mass lesions as the lens eroded into the lid. There were no external features to point to the correct diagnosis. In both cases a round hole in the conjunctiva over the embedded lens was noted, and the authors also noted this finding in clinical photographs from other case reports in the literature. This finding, the "O" sign, should suggest the possibility of a lost hard contact lens embedded in the upper lid.