The Role of the Back Plate in Angle Anatomy with the Boston Type I Keratoprosthesis

Purpose: To quantitatively evaluate the angle anatomy in eyes with the Boston type I keratoprosthesis (B-KPro) differing in the back plate (BP) material and size using anterior segment optical coherence tomography. Methods: B-KPro eyes with poly(methyl methacrylate) (PMMA) (7.0 and 8.5 mm) and titanium (7.0, 8.5, and 9.5 mm) BPs were imaged with anterior segment optical coherence tomography. The angle opening distance at 500 mu m from the scleral spur (AOD500), trabecular iris surface area at 500 mu m from the scleral spur (TISA500), and trabecular iris angle at 500 1.1m from the scleral spur (TIA500) were measured. Among the visible quadrants, the average, the temporal, the widest, and the narrowest angle of each eye were included in the analysis. Average time between B-KPro implantation and imaging was 7.5 +/- 1.4 years for a PMMA BP and 2.4 +/- 2.3 years for a titanium BP (P < 0.0001). Results: We analyzed 17 B-KPro eyes with PMMA BPs and 24 B-KPro eyes with titanium BPs. The average AOD500 (394.1 +/- 226.9 vs. 454.5 +/- 255.6 mu m, P = 0.44), average TIA500 (26.2 +/- 14.2 vs. 29.8 +/- 13.9 degrees, P = 0.43), and average TISA500 (0.15 +/- 0.08 vs. 0.17 +/- 0.10 mu m(2), P = 0.52) were not statistically different between eyes with PMMA and titanium BPs, nor were the temporal, the narrowest, and the widest angle measurements of each eye (all P > 0.05). Similarly, no significant differences were found between the angle measurements of B-KPro eyes with a titanium BP diameter of 8.5 or 9.5 mm (all P > 0.05). Conclusions: We successfully visualized the angle anatomy in 66.1% of the imaged eyes, including all BPs studied. Neither the material nor the size of the B-KPro BP had a significant impact on the angle anatomy.