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. 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. 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. 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.

To evaluate the incidence, associations, and visual outcomes in patients with diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK). University-based refractive surgery center, Boston, Massachusetts, USA. This retrospective review comprised 2711 eyes that had LASIK between September 1996 and September 1999. All eyes that developed DLK after LASIK were included. They were divided into type I DLK (center sparing) or type II DLK (center involved) and then subdivided into A (sporadic-DLK not diagnosed in other patients treated on the same day) or B (cluster-other patients identified with DLK). Type IA corresponded to center sparing, sporadic; type IB, center sparing, cluster; type IIA, center involved, sporadic; and type IIB, center involved, cluster. The main outcome measures were incidence of DLK after LASIK, time to diagnosis, time to resolution, and changes in best spectacle-corrected visual acuity (BSCVA). Unpaired t tests were used for statistical analyses. Thirty-six eyes (1.3%) developed DLK. Type I occurred in 58.3% of cases (type IA, n = 18; type IB, n = 3) and type II, in 41.7% (type IIA, n = 10; type IIB, n = 5). The mean time to diagnosis was not statistically significantly different between type I (1.8 days) and type II (1.1 days). Fourteen eyes (38.9%) developed DLK after an epithelial defect, representing an odds ratio of 13 times. The association with an epithelial defect was statistically significantly greater with type I (11/21 eyes, 52.4%) than with type II (3/15 eyes, 20.0%; P =.05). The mean time to resolution was 3.5 days in type I (type IA = 3.6 days; type IB = 2.7 days). This was significantly shorter than in type II, which had a mean time to resolution of 12.1 days (type IIA = 9.3 days; type IIB = 10.2 days) (P =.001). Loss of 2 or more lines of BSCVA occurred in 2 of 5 patients with type IIB and in no patients with types IA, IB, or IIA. Epithelial defects after LASIK increased the risk of DLK occurrence, especially type I. Type II DLK was associated with a prolonged time to resolution and carried a significantly higher risk of BSCVA loss than type I.