Though many surgeries deliver their best results for patients upon first use and diminishing returns for any subsequent procedure, repeat penetrating keratoplasty (PK) may have a stronger healing response at the corneal graft edge than primary PK, a study in Cornea reports.

Since graft failure has become an increasing indication for repeat PK, the study evaluated and compared the biomechanical properties of the transplanted cornea and how they correlated with the healing process at the graft edge after primary and repeat PK.

The retrospective investigation, conducted in Egypt, included 35 eyes of 35 patients with PK, 40 eyes of 40 patients who had repeat PK and a control group consisted of 20 eyes of 20 normal subjects. The study measured and compared corneal hysteresis and corneal resistance factor among the groups at least six months after all sutures were removed. The investigation also used in vivo confocal microscopy to study the corneal wound healing process at the graft edge in PK and repeat PK groups and to correlate these findings with corneal biomechanics.

The study found corneal hysteresis and corneal resistance factor were significantly lower in the PK group (6.71 ± 1.3mm Hg and 5.99 ± 1.2mm Hg, respectively) when compared with the repeat PK group (9.4 ± 1.03mm Hg and 8.77 ± 1.1mm Hg, respectively). The repeat PK group also demonstrated biomechanical parameters comparable with normal subjects. Confocal microscopy revealed more reflective and activated keratocytes at the graft edge in the repeat PK group compared with the primary PK group.

“I hypothesize that the repeat surgery in the repeat PK group induced a stronger healing response at the corneal graft edge, increasing its mechanical strength,” Almamoun Abdelkader, MD, the study’s sole author, wrote in his paper. “The repeated surgery may induce a foreign body reaction at the circumferential graft edge between donor and recipient tissues, stimulating an influx of inflammatory cells, a transformation of myofibroblasts, and a synthesis of new stromal ground substance.”

He added that the healing at the graft edge is crucial to corneal integrity after PK. Repeat PK caused a stronger healing process by stimulating more activated keratocytes than primary PK, which provides superior corneal biomechanics comparable with the control group.


Abdelkader A. Changes in corneal wound healing and graft biomechanics after primary penetrating keratoplasty versus repeat penetrating keratoplasty. Cornea. March 18, 2019. [Epub ahead of print].