Predicting Graft Survival After PK

Corneal transplantation is the most commonly performed solid-tissue transplant procedure in the world. Corneal surgeons regularly perform various forms of corneal transplantation to treat corneal blindness, including penetrating keratoplasty (PK). Zeba A. Syed, Co-Director of the Cornea Fellowship Program at Wills Eye, comments, “Often, when we counsel patients prior to PK, they will ask us about the chances of their transplant being successful after five years.”

Typically, corneal surgeons will answer this question with a ballpark prediction based on their individual anecdotal experiences. Though numerous studies have identified risk factors for graft failure, there currently exists no mathematical tool that surgeons can use to make a personalized calculation for the chance of long-term PK success based on a patient’s known risk factors.

“When I joined the Cornea Service as a faculty member at Wills Eye Hospital two years ago, developing this mathematical model, or ‘nomogram’ – predicting PK graft survival – became my primary research goal,” Syed explains. “Working with Eric Shiuey, an outstanding medical student from the Sidney Kimmel Medical College at Thomas Jefferson University, we reviewed over 1,000 PKs performed at Wills Eye from May 2007 to September 2018. We evaluated 36 preoperative and intraoperative variables with multivariate models, and created a nomogram to predict the probability of PK graft survival at postoperative years three and five.”

The team’s multivariate analysis identified 11 variables significantly associated with PK graft failure, a few of which included active infection at the time of PK, intraocular silicone oil, systemic autoimmune disease, and corneal neovascularization. The nomogram that was developed for PK survival based on these 11 variables exhibited an accuracy of 76 percent at 3 and 5 years after internal testing.

“We concluded that PK graft prognosis may be modeled with a relatively high accuracy based on 11 preoperative and intraoperative variables,” notes Syed. “This nomogram could play a key role in comprehensive and data-driven patient counseling prior to corneal transplantation.”