Epithelial Downgrowth After Type 1 Boston Keratoprosthesis Manifesting as Tractional Retinal Detachment and Epiretinal Membrane

Type 1 Boston keratoprosthesis (KPro) is a viable treatment option for corneal disease at high risk for graft failure with traditional penetrating keratoplasty. Postoperative complications of Boston KPro include retroprosthetic membrane, glaucoma, sterile vitritis, infectious endophthalmitis, corneal melt, extrusion, and retinal detachment.¹ To our knowledge, we report the first case of epithelial downgrowth (ED) of the posterior segment after Boston KPro placement.

A 52-year-old man with a history of penetrating ocular injury to his right eye had open globe repair and cataract extraction in 1974, placement of a secondary anterior chamber intraocular lens in 1992, 2 failed penetrating keratoplasty procedures in 2004 and 2008, Baerveldt glaucoma tube implantation in 2005, astigmatic keratotomy in 2007, and, most recently, intraocular lens removal and type 1 Boston KPro placement in 2010. Histologic examination of the failed corneal graft excised at the time of KPro placement did not demonstrate ED. One week after KPro placement, visual acuity was 20/40 OD. Two months after KPro placement, he had pain and photophobia in the right eye.

At his visit to us, visual acuity was 8/200 OD and 20/20 OS. No afferent pupillary defect was identified. Intraocular pressure was soft to palpation OD and 14 mm Hg OS. Slitlamp examination revealed an intraprosthetic membrane (Figure 1A). B-scan ultrasonography revealed anterior vitreous bands, tractional retinal detachment (TRD), and a small choroidal detachment (Figure 1B). Review of B-scan ultrasonographic images performed 2 months previously, before KPro placement, showed a normal posterior segment. A 23-gauge pars plana vitrectomy was performed to repair the TRD. Pars plana vitrectomy revealed a dense anterior vitreous band contiguous with a TRD and epiretinal membrane (ERM) extending across the macula. Extensive membrane peeling was performed, followed by fluid-air exchange, endolaser, and silicone oil injection. A large ERM specimen from the macula was sent for histopathologic evaluation. Microscopic evaluation of the ERM revealed mucosal epithelium containing goblet cells on hematoxylin-eosin, periodic acid–Schiff base, and Masson-Trichrome staining, consistent with ED (Figure 2). Immunohistochemical analysis with cytokeratin showed positive staining, revealing epithelial cells lining one side of the ERM (Figure 2). At the patient's 2-month follow-up, slitlamp examination revealed recurrent intraprosthetic membrane and flat retina by indirect ophthalmoscopy and optical coherence tomography.

Epithelial downgrowth of the posterior segment is rare but can manifest within months after eye surgery. McDonnell et al² reported ED occurring 3 months after ruptured globe repair, lensectomy, and pars plana vitrectomy, wherein TRD and ERM were found to consist of nonkeratinized, stratified squamous epithelium. Our case demonstrates a similar rapid progression of ED into the posterior segment after surgery. B-scan ultrasonography documented a normal-appearing posterior segment before KPro placement. Two months after KPro placement, B-scan ultrasonography showed the large TRD due to ED.

Epithelial downgrowth after KPro placement has been a subject of historical interest. Girard³ observed that ED only occurred in early KPro models previous to 1972. The Boston KPro was approved by the US Food and Drug Administration in 1992 and has demonstrated ED in only 2 cases. Both cases had ED localized to the anterior chamber due to full-thickness tissue melting at the KPro-cornea junction from ocular cicatricial pemphigoid.⁴ To our knowledge, there have been no published reports of ED after Boston KPro placement involving the posterior segment. In our case, histologic review confirmed that ED of the posterior segment occurred after KPro placement.

Histopathologic findings of ED typically consist of nonkeratinized, stratified squamous or conjunctival epithelium extending over the posterior cornea or anterior surface of the iris from an anterior wound site. In phakic or pseudophakic eyes, the posterior lens capsule serves as a barrier preventing further advancement of the epithelium into deeper structures of the eye. Epithelial downgrowth of the posterior segment can occur when this barrier has been disrupted (aphakia, lens luxation or subluxation, iridodialysis) or bypassed (trauma, scleral buckle intrusion).⁵

Many treatments for ED have been described, including cryotherapy, radiation, alcohol, steroids, antimetabolites such as fluorouracil, and complex surgical procedures, each with varying rates of success and recurrence.^6,7 Although our case demonstrates successful surgical repair of the TRD, the likelihood of ED disease progression remains high. Further study is needed to better understand the etiology, diagnosis, and management of ED in this clinical setting.

Correspondence: Dr Berrocal, Bascom Palmer Eye Institute, Miller School of Medicine, University of Miami, 900 NW 17th St, Miami, FL 33136 (aberrocal@med.miami.edu).

Additional Contributions: Candace Waithe-Boodoo, Randall Hughes, Sarah Miller, CRA, and Alexander Rodriguez, CRA contributed to data and photograph collection.