Long-term Outcomes of the Aphakic Snap-on Boston Type I Keratoprosthesis at the Bascom Palmer Eye Institute

Purpose: To determine the indications, long-term clinical and visual outcomes, and complications of the aphakic snap-on type I Boston keratoprosthesis (KPro).

Design: Retrospective, non-comparative case series.

Methods: Forty-five eyes of 43 patients with type I aphakic snap-on KPros with at least 1 year of follow-up were included. The past medical histories, preoperative indications, best-corrected visual acuities (BCVAs), postoperative complications, and retention rates were analyzed.

Results: The most common indication for KPro implantation was a failed corneal graft (89%). The mean preoperative BCVA was count fingers-hand motion (2.14±0.45 logarithm of minimum angle of resolution [logMAR]), which initially improved to 20/200 (1.04±0.85 logMAR; <0.0001). At the last examination, 24 eyes (53%) maintained some visual gain, 22% retained their preoperative visual acuity, and 24% lost vision due to postoperative events and underlying ocular comorbidities. Postoperative complications included retroprosthetic membranes (8/45, 18%), corneal melts (5/45, 11%), glaucoma progression (6/45, 13%), and endophthalmitis or sterile vitritis (6/45, 13%). The KPro retention rate was 89%, with a mean follow-up of 51 months. The mean BCVA at the last visit was 20/1,400 (1.82±0.92 logMAR).

Conclusion: Most patients experienced improved visual acuity after the implantation of the aphakic, snap-on type I KPro; however, the visual gains were not sustained over time, correlating with the onset of postoperative complications.