Fig. 33. A case of iris prolapse through a limbal wound. A. A large black mass has appeared at the limbus of a patient with a history of cataract extraction. There may or may not be a history of trauma or Valsalva maneuver. The differential diagnosis at first glance would certainly include primary conjunctival malignant melanoma or extraocular extension of a primary uveal malignant melanoma. A major differential observation from iris prolapse is the character and degree of alteration of the iris tissue remaining within the eye. B. By histologic section no cellular mass is present either in the episcleral or uveal tissue. The remaining iris is stretched and adherent to the posterior corneal surface. (Hematoxylin-eosin stain; × 40.)