Epithelial Downgrowth Mimicking Recurrent Retroprosthetic Membrane After Boston Keratoprosthesis Implantation

To report a case of epithelial downgrowth mimicking recurrent retroprosthetic membrane (RPM) in a patient with a Boston Keratoprosthesis (KPro).

Case report and literature review.

A 74-year-old monocular man with a history of penetrating corneal injury and multiple failed penetrating corneal transplants in the left eye followed by a Boston KPro type 1 implantation presented with decreased visual acuity from baseline 20/70 to 20/200. Examination revealed opaque material posterior to the optical element of the KPro, which was interpreted to be an RPM. The patient was treated with yttrium aluminum garnet laser membranectomy with immediate improvement in vision to baseline. He subsequently developed frequent recurrences of this visually significant membrane, each recurring in less than 7 days, and each responding to yttrium aluminum garnet membranectomy with return to baseline vision. Because of concerns about the frequency of visits required, the patient requested that the KPro be removed and replaced with a corneal allograft. Histopathologic evaluation of the submitted specimen demonstrated stratified, nonkeratinizing squamous epithelium on the posterior surface of the carrier cornea and optical element, consistent with epithelial downgrowth.

Epithelial downgrowth is a rare complication of KPro implantation and should be suspected in patients with frequently and rapidly recurrent RPMs.