Fig. 44. A case of epithelial downgrowth. A. The clinical findings are subtle and consist of a translucentmembrane on the posterior corneal surface, often contiguous with an ocular wound, characterized by a well-defined, linear leading edge. In this case, the leading edge is just above the corneal light reflex. B. In contrast, in this case, the leading edge is just below the corneal light reflex. The surgical procedure in both cases appears to have been complicated because of the presence of sector iridectomies. C. In this case, surface stratified squamous epithelium lines the posterior cornea (including the posterior aspect of the clear corneal wound) and extends over delicate trabecular tissue onto the anterior surface of the iris. The epithelium will adapt the tissue over which it grows to produce an adhesive surface appropriate to its attachment requirements. This adaptive process that is an advantage for the epithelium will permanently destroy the function of the trabecular meshwork over which the surface epithelium extends. D. The actual site of the fistula allowing the epithelium to gain access to the internal surfaces of the eye is rarely found on histologic sections. Higher magnification of the area of the wound, however, does show the presence of foreign material in the incision. Polarized material (inset) consistent with degenerating silk suture is present. Invasion of the epithelium along a suture tract is one possible route of entrance. (Hematoxylin-eosin stain with and without polarization; A, × 21; B, × 101)