Long-term visual outcomes of the Boston type I keratoprosthesis in Canada

Background/aims To evaluate long-term visual outcomes of Boston type I keratoprosthesis (KPro) surgery and identify risk factors for visual failure. Methods Single surgeon retrospective cohort study including 85 eyes of 74 patients who underwent KPro implantation to treat severe ocular surface disease, including limbal stem cell deficiency, postinfectious keratitis, aniridia and chemical burns. Procedures were performed at the Centre hospitalier de l'Universite de Montreal from October 2008 to May 2012. All patients with at least 5 years of follow-up were included in the analysis, including eyes with repeated KPro. Main outcome measures were visual acuity (VA), visual failure, defined as a sustained worse than preoperative VA, postoperative complications, and device retention. Results Mean follow-up was 7.2 +/- 1.3 years (+/- SD). Mean VA was 2.1 +/- 0.7 (logarithm of minimal angle resolution) preoperatively and 1.9 +/- 1.2 at last follow-up. There were 2.4% of patients with VA better than 20/200 preoperatively and 36.5% at last follow-up. Maintenance of improved postoperative VA was seen in 61.8% of eyes at 7 years. Preoperative factors associated with visual failure were known history of glaucoma (HR=2.7 (1.2 to 5.9), p=0.02) and Stevens-Johnson syndrome (HR=7.3 (2.5 to 21.4) p<0.01). Cumulative 8-year complication rates were 38.8% retroprosthetic membrane formation, 25.9% hypotony, 23.5% new onset glaucoma, 17.6% retinal detachment, 8.2% device extrusion and 5.9% endophthalmitis. The majority (91.8%) of eyes retained the device 8 years after implantation. Conclusion Almost two-thirds of patients had improved VA 7 years after KPro implantation. Preoperative risk factors for visual failure were known glaucoma and Stevens-Johnson syndrome.