Most Kpro eyes with pre-existing glaucoma suffered from glaucoma progression that continued throughout the follow-up period. Photo: Brandon Ayres, MD. Click image to enlarge.

Multiple studies have shown favorable outcomes for the Boston Keratoprosthesis type 1 (Kpro) in high-risk eyes, but most of them were based on short/mid-term follow-up data. In a new study, researchers evaluated long-term outcomes of patients and found that glaucoma is directly correlated with the duration of Kpro implantation.

A total of 75 patients who underwent KPro surgery between 2006 and 2012 and 17 patients with at least 10 years of follow-up were included. Demographics, ocular history, surgery indication, clinical variables and postsurgical outcomes were recorded.

At the final follow-up, about two thirds of eyes retained the original Kpro device. About half of those experienced an improvement in VA, but the final VA remained 20/200. Just over 40% of eyes had worse VA compared with before Kpro surgery.

Major complications such as infectious keratitis, hypotony, retinal detachment, endophthalmitis and retroprosthetic membrane developed. The authors noted that these were typically associated with poor final VA in the hand motions range. Only one of 17 eyes maintained its best-ever VA, suggesting long-term VA prognosis after Kpro surgery is guarded. The overall retention proportion including repeat implantation was 82.3%.

“Our study’s findings are consistent with current literature that the main reason for vision loss in eyes with Kpro is typically glaucoma progression,” the researchers wrote in their paper for Cornea. “A clinical case-control study found that only a minority of Kpro eyes never developed glaucoma over a mean follow-up period of 6.9 years and that most Kpro eyes with preexisting glaucoma suffered from glaucoma progression that continued throughout the follow-up period. By seven years, 21.6% of eyes had development or progression of glaucoma. Our study showed a higher prevalence, with about half of our patients with glaucoma development or progression requiring glaucoma surgeries after Kpro implantation.”

The high prevalence of glaucoma development or progression suggests that glaucoma development or progression is positively correlated with the duration of Kpro implantation.

“In summary, the survival/retention proportion of Boston type 1 KPro implants in our cohort remained high at 80% at 10 years, suggesting that most KPro implants are anatomically compatible with the human eye over long periods,” the authors concluded. “However, postoperative complications are frequent, leading to loss of best-ever postoperative visual acuity. Although our study was limited by its small sample size and retrospective nature, our findings highlight the need for further research to create a better KPro design for patients with complex anterior segment pathologies.”