Type I to type II Boston keratoprosthesis exchange: a report of two patients

BACKGROUND: To report two cases of Boston Keratoprosthesis (BKPro) type I failure in patients with severe ocular surface disease and to describe the successful replacement of the BKPro type 1 with a BKPro type II, highlighting clinical indications, surgical considerations, and postoperative outcomes. This is a case report of two patients with a history of complex ocular surface pathology-one with Stevens-Johnson Syndrome and the other with bilateral chemical burns-both of whom had previously undergone type I BKPro implantation and subsequently developed complications including corneal melt and backplate exposure. Clinical presentation, surgical intervention, and follow-up are detailed. A literature review was conducted to identify previously reported cases and recommendations regarding type I BKPro replacement with type II BKPro. CASE PRESENTATION: Both patients underwent successful explantation of the type I BKPro and implantation of a type II BKPro in a combined procedure with pars plana vitrectomy. In one case, corneal melt around the type 1 BKPro developed in the setting of Stevens-Johnson Syndrome prompting replacement with a type 2 BKPro. In the second case, dacryoadenectomy may have contributed to ocular surface instability and corneal melt. Visual acuity improved in both cases postoperatively, with stable device positioning and no signs of infection or retinal complications at last follow-up. CONCLUSIONS: Transitioning from type I BKPro to type II is a feasible and effective strategy in patients with severe ocular surface disease and BKPro failure due to corneal melt in the setting of history of Stevens Johnson Syndrome and chemical injury.