Long-term safety and efficacy of high-fluence collagen crosslinking of the vehicle cornea in Boston keratoprosthesis type 1.

The aim of this study was to evaluate the safety and efficacy of very high-fluence collagen crosslinking (CXL) as a means of achieving increased corneal rigidity and reduced enzymatic digestion in the vehicle cornea of Boston keratoprosthesis (KPro) type 1. Eleven consecutive patients fitted with a KPro (5 with a previous repeat cornea graft failure, 4 with ocular cicatricial pemphigoid, and 2 with chemical burn) underwent donor vehicle cornea pretreatment with very high-fluence prophylactic CXL in a 2-step procedure. First, the donor cornea was crosslinked with an intrastromal riboflavin instillation through a femtosecond laser-created pocket. This was followed up with a superficial CXL treatment. On the completion of the CXL pretreatment, the cornea center was trephined with the femtosecond laser, and the KPro was fitted onto the crosslinked donor cornea. Visual acuity, corneal surface, and donor vehicle cornea stability were evaluated. Follow-up evaluations were conducted over the next 9 years with a mean of 7.5 years. Mean uncorrected visual acuity improved from light perception to 20/60. One patient required a follow-up surgery, because of significant melt in the host cornea. None of the eyes developed melts and/or infection, especially on the vehicle cornea on which the KPro was fitted. Pretreatment with intrastromal and superficial very high-fluence CXL in conjunction with Boston type 1 KPro seems to be a safe and effective adjunctive treatment for achieving increased vehicle donor cornea rigidity. Additionally, there is an increased resistance to enzymatic degradation. This application may serve to enhance the biomechanical stability and external disease resistance of the donor vehicle cornea in patients with advanced external disease.