Noninvasive Diagnosis of Epithelial Downgrowth After Penetrating Keratoplasty Using Immunohistochemical Analysis of Resected Corneal Buttons

Purpose: To describe a noninvasive technique that can be used to support a clinically suspected diagnosis of epithelial downgrowth in patients who have previously undergone penetrating keratoplasty (PK). Methods: Previously resected corneal buttons of 14 patients who developed signs suggestive of epithelial downgrowth after PK were examined retrospectively using immunohistochemical analysis to determine if occult epithelial cells were in fact present on the posterior surface of the cornea. Many of these patients were diagnosed with pseudophakic corneal edema or graft failure and had undergone multiple intraocular surgical procedures. In all cases, the initial histopathologic evaluation did not disclose the presence of epithelial cells using light microscopy after standard handling and staining techniques. Fourteen age- and diagnosis-matched control specimens were also examined. Results: Thirteen of 14 specimens (92.9%) exhibited positive staining with anti-keratin AE1/AE3 markers, indicating that epithelial cells were already present on the endothelial surface at the time of the original PK. None of the control specimens displayed positive staining of the retrocorneal surface. Conclusion: Retrospective immunohistochemical analysis of corneal specimens can establish the diagnosis of epithelial downgrowth in a noninvasive manner. Early diagnosis may allow for this condition to be treated more successfully if aggressive intervention is undertaken. Alternatively, it may spare the patient from additional (and potentially futile) intraocular surgery. In the clinical setting of suspected epithelial downgrowth, ophthalmic pathologists should re-evaluate PK specimens from patients initially diagnosed with pseudophakic corneal edema or graft failure.