The Boston keratoprosthesis 2014: a step in the evolution of artificial corneas

Abstract

“Artificial corneas” have been attempted in severe corneal disease for at least 230 years, with largely disappointing results until recently. ‘The Boston Keratoprosthesis’ (B-Kpro) has been part of this history on and off for a half century. Developed from several previously known concepts, it was originally made of PMMA plastics in a collar button design (Type I), to be implanted into a corneal graft carrier and then transplanted to the patients’ cornea. (A Type II with an additional stem for lid penetration is occasionally used in end-stage dry eyes.)Management and device changes have over the years led to marked clinical improvements. Thus, postoperative infections have been drastically reduced by using low-dose prophylactic antibiotics. The corneal surface has been found to be well protected from evaporative damage by a soft contact lens or a conjunctional flap. Postoperative tissue melt around the device has been markedly reduced by improvement of nutrition from the aqueous (perforated back plates) and better anti-inflammatory strategies. Titanium alloys can be used for non-transparent parts to reduce inflammation and increase biointegration. Retroprosthesis membranes and retina complications have similarly been markedly reduced. However, post-operative glaucoma is still a stubborn problem that can cause long-term attrition of vision. Autoimmune diseases are particularly treacherous and B-KPros should not at present be used routinely. About 12,000 Boston Keratoprostheses have so far been distributed world-wide. Robust research is presently on-going to improve long-term safety, especially for the developing world.