Date Published: February 6, 2018
Publisher: Public Library of Science
Author(s): Kai B. Kang, Faris I. Karas, Ruju Rai, Joelle A. Hallak, Joann J. Kang, Jose de la Cruz, Maria S. Cortina, Demetrios G. Vavvas.
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.
First approved by the U.S. Food and Drug Administration in 1992, the Boston type 1 Keratoprosthesis (KPro) has undergone many iterative modifications in device design, surgical technique, postoperative management and reduced rates of complications [1–3]. This artificial cornea has now become a legitimate, well-established tool in our armamentarium for treating patients with debilitating corneal blindness[4–7]. KPro surgery has traditionally been thought of as a procedure of last resort. Despite improved retention and reduced complication rates paving the way for the current dramatic expansion of applications and surge in prevalence for the KPro, the most frequent indication for its placement today remains prior graft failure[4,5,8–12].
This research has been approved by the University of Illinois Office for the Protection of Research Subjects and has been conducted according to the principles expressed in the Declaration of Helsinki. All data were fully anonymized before access by the researchers and informed consent was waived by the Office for the Protection of Research Subjects. A retrospective, matched cohort study was conducted based on a chart review on all patients who underwent KPro (Boston type 1 keratoprosthesis, Woburn, MA) implantation at the University of Illinois Eye and Ear Infirmary (IEEI) by two artificial cornea surgeons (J. de la C., M.S.C.) between July 2008 and October 2014.
Boston type 1 keratoprosthesis is an increasingly popular option for patients with poor prognosis for traditional keratoplasty. When to offer this procedure in the course of corneal disease is still a matter of discussion as we lack evidence to support clear indication guidelines. However, there is a group of patients, particularly those with bilateral limbal stem cell deficiency and other severe forms of ocular surface disease that may benefit from this procedure early. Despite the need for good randomized clinical trials that compare treatment options in these patients, there is some evidence that suggests that in fact KPro may have better outcomes than other forms of surgical therapy[18,23–25]. Our study shows that KPro implantation as the primary procedure has good long-term retention and visual acuity results. Furthermore, it suggests that earlier intervention in a specific subset of patients may result in better visual outcomes when compared to KPro as a secondary or rescue procedure without an increased risk and/or severity of complications.
Our evidence supports the use of KPro implantation as the primary corneal procedure in patients with severe corneal and ocular surface disease. By matching patients with similar preoperative diagnosis and demographics, our study is able to more specifically compare outcomes between primary and secondary KPro. We showed that in a matched-case control setting, primary KPro patients achieved superior visual recovery and maintenance of post-operative visual acuity than secondary KPro.