Purpose: Necrosis, melt, and perforation have historically been frequent around a Keratoprosthesis (KPro), even resulting in extrusion or endophthalmitis. Autoimmune diseases such as Stevens-Johnson Syndrome (SJS) and Ocular Cicatricial Pemphigoid (OCP) have been notorious in this respect. The purpose of this study was to compare the frequency of tissue melt after implantation of two designs of the Boston KPro, one allowing much better access of nutrition from the aqueous humor to the carrier graft. Methods: We retrospectively reviewed charts of 157 eyes implanted since 1990 with a poly (methylmethacrylate) Boston KPro, including 79 eyes implanted with the model having 8 small (1.3-mm diameter) holes in the back plate, and 78 eyes implanted with the older solid back plate. We compared the frequency of tissue melts between the two KPro designs, for all implants as well as for subgroups based on preoperative diagnosis. Results: In total, 48/157 eyes (31%) developed some degree of tissue melt around the stem, including 8/79 eyes (10%) in the back plate with holes group and 40/78 eyes (51%) in the solid back plate group (P < 0.0001). Among the melts in the back plate with holes group, 4/8 (50%) suffered from an underlying autoimmune disease such as SJS or OCP. Conclusions: The Boston KPro design with a back plate containing holes protects the overlying corneal tissue from necrosis and melts. This improved situation is likely due to increased aqueous access and better nutrition to the corneal graft cells. In addition, this study confirms earlier work regarding the particular corneal fragility of patients with autoimmune diseases.
