Five year outcomes of Boston type I keratoprosthesis as primary versus secondary penetrating corneal procedure in a matched case control study

Abstract

Despite improved retention and reduced complication rates paving the way for the current expansion of applications and surge in prevalence for the Boston type I Keratoprosthesis (KPro), the most frequent indication for its implantation today remains prior graft failure. The purpose of this study is to evaluate the long-term outcomes of primary KPro and compare to secondary implantation in a matched cohort study. This study included patients who underwent KPro implantation in a single center by two surgeons between July 2008 and October 2014. All eyes with KPro implantation as the primary procedure with a minimum follow up of 12 months were matched with eyes with same preoperative diagnoses that underwent secondary KPro implantation. Main outcomes included visual acuity and device retention. A total of 56 eyes were included with 28 eyes in each group. Mean follow up was 5.0 years for both groups. Twenty-nine percent (8) of the eyes in the primary group had a diagnosis of chemical or thermal injuries, 25% (7) aniridia, 18% (5) autoimmune disease, 4% (1) infectious keratitis/neurotrophic cornea, 7% (2) gelatinous corneal dystrophy, 7% (2) ectrodactyly ectodermal dysplasia/limbal stem cell deficiency, and 11% (3) uveitis/hypotony. Sixty-one percent (17) of the eyes in the primary group and 39% (11) in the secondary group maintained a final best-corrected visual acuity of 20/200 or better at a mean follow up of 5.0 years; the probability of maintaining best-corrected vision is 0.83 and 0.49 for primary and secondary groups at 5.0 years (p = 0.02). There is no statistically significant difference between groups in device retention (p = 0.22) or postoperative complication rates (p >0.05). This study demonstrates that Boston KPro implantation may be successful as a primary procedure in patients at high risk of failure with traditional penetrating keratoplasty. The device has a good long-term retention rate and visual outcomes are promising however a larger study is needed for more definitive results.

Fig 1. Survival of visual acuity.

Graph showing best-corrected visual acuity survival curves for both primary and secondary groups. X-axis demonstrates post-operative months, and y-axis demonstrates survival of best-corrected visual acuity (e.g 1.0 = 100% of the eyes maintaining best-corrected post-operative visual acuity). P-value was calculated using Log-rank test. Table below shows the number of eyes followed at each time point.

Fig 2. Device retention.

Graph showing KPro survival curves for both primary and secondary groups. X-axis demonstrates post-operative months, and y-axis demonstrates KPro survival (e.g. 1.0 = 100% of the eyes with device retention). P-value was calculated using Log-rank test. Table below shows the number of eyes followed at each time point.