Background/aims To compare long-term outcomes of primary versus secondary (postgraft failure) Boston keratoprosthesis type 1 (KPro) implantation.

Methods Medical records of patients at the Centre hospitalier de l’Université de Montréal having undergone KPro implantation between 2008 and 2017 were reviewed and included if they had a preoperative Snellen best-corrected visual acuity (BCVA) of 20/100 or worse and a minimum of 5 years of follow-up. Eighty-two eyes were separated into two cohorts (40 primary, 42 secondary KPro) and BCVA, complications and device retention were evaluated between groups.

Results BCVA improved from baseline in both groups at each year; this was significant at all five postoperative years in the primary group and the first 3 years in the secondary group (p<0.05). Mean BCVA was similar between groups at 5 years (logarithm of minimal angle resolution 1.3±0.8 in the primary group vs 1.5±0.8 p<0.05). Idiopathic vitritis, choroidal detachment and new glaucoma occurred more after primary KPro (n=7, 17.5% vs n=1, 2.4%; n=11, 27.5% vs n=3, 7.14% and n=14, 35% vs n=6, 14%, respectively; p<0.05). Primary KPro had lower retention (n=28, 70% vs n=38, 91%, p<0.05) at final follow-up. There was more aniridia in the primary group (n=19, 48% vs n=6, 14%, p<0.01). Within each group, 50% of removals occurred in aniridic eyes.

Conclusion Primary KPro yielded favourable long-term visual outcomes but had more complications and lower retention rates than secondary KPro, likely explained by preoperative indications. Primary device implantation represents a favourable option for patients for whom grafts are likely to fail.