Differential Diagnosis between Corneal Intraepithelial Neoplasia and Conjunctival Epithelial Invasion by Impression Cytology

The differential diagnosis of noninflammatory peripheral corneal epithelial haze of unknown etiology includes corneal intraepithelial neoplasia and conjunctival epithelial invasion. However, on the basis of the clinical manifestations alone, it is difficult to distinguish between these two entities. The purpose of this study was to evaluate the efficacy of impression cytology in the differential diagnosis of these two conditions. Six eyes from six consecutive patients with noninflammatory peripheral corneal epithelial haze of unknown etiology, who presented to our clinic between September 1993 and December 1995, were enrolled in this study. In all of the eyes, the haze mainly affected the epithelial layers and arose at the limbus. To determine whether goblet cells were present in the involved epithelium, impression cytology was performed. In three eyes, a large number of goblet cells were found in the affected regions, thus indicating that the etiology was conjunctival epithelial invasion. In contrast, in the other three eyes, larger squamous cells, but not goblet cells, were found; this was suggestive of corneal epithelial neoplasia. In two of the latter cases, a pathological examination of the tissues excised at surgery confirmed the above diagnosis. These results indicate that impression cytology of the affected region is important to the accurate diagnosis of noninflammatory peripheral corneal epithelial haze.