Boston Type 1 Keratoprosthesis: Updated Perspectives

Abstract

The use of Boston type 1 keratoprosthesis (BKPro) has significantly increased worldwide. It is no longer considered a procedure of last resort but a reasonable option for patients with otherwise poor prognosis for a traditional penetrating keratoplasty. BKPro was approved by the Food and Drug Administration in 1992 for bilateral severe corneal blindness due to multiple corneal transplant failure. Over the years, indications have extended beyond recurrent immunologic rejection to include other conditions such as chemical injury and other causes of bilateral limbal stem cell deficiency, extensive corneal neovascularization, neurotrophic corneas and hypotony, among others. Numerous advances in the design of the BKPro, improvement of preoperative, intraoperative and postoperative management have resulted in favorable outcomes and a reduction in postoperative complications. Accordingly, many studies have shown that implantation of this device is highly effective in restoring vision with very good short-term outcomes. However, due to the lifetime risk of sight-threatening complications after BKPro implantation, a longer follow-up period should provide outcomes that are more realistic. In this review, the authors examined only the results of publications with an average of at least 2 years of follow-up. The overall intermediate to long-term visual outcomes and retention rate in BKPro seem to be favorable. However, autoimmune diseases and cicatrizing conditions continue to show a higher incidence of postoperative complications that require further management.

Keywords: Boston keratoprosthesis; corneal transplantation; limbal stem cell deficiency.

Figure 1

Type I Boston keratoprosthesis.

Figure 2

Patient with implanted type 1 Boston keratoprosthesis. (A) Anterior segment OCT showing sterile corneal melt. There is evidence of back plate exposure (*). (B) One week after graft replacement without removing the keratoprosthesis for the treatment of corneal melt. (C) Postoperative anterior segment OCT showing good graft apposition with the KPro optical stem in the same patient.

Figure 3

Slit-lamp photograph of a patient with BKPro I implant combined with pars plana glaucoma drainage device (GDD) 8 years ago. This approach allowed good contact lens fitting and eliminated friction between the contact lens and plate/tube of GDD. Kontur lens base curve 8.9 and diameter 16 mm is in place.