Characteristics and risk factors of recurrent keratoconus over the long term after penetrating keratoplasty

Purpose: To determine the characteristics and risk factors of recurrent keratoconus (KC) after penetrating keratoplasty (PK).

Methods: We enrolled patients who had maintained clear grafts for at least 10 years after PK based on their medical records. Patients were divided into the KC group or Others group based on the primary indication for PK. Each case was reviewed for clinically observed corneal ectasia. Steepest keratometric power (Ks), cylinder (CYL), and difference between Ks and minimum keratometric power (MinK) were analyzed in patients that underwent corneal topography more than three times after the 5th postoperative year.

Results: One hundred one eyes of 82 patients were enrolled. The KC group comprised 50 eyes and the Others group comprised 51 eyes (herpes [n = 22], corneal leukoma [n = 12], and other [n = 17]). The mean period after PK was 27.2 years in the KC group and 26.0 years in the Others group. Recurrent KCs were observed in 18 eyes of 14 patients (36%), all of whom were in the KC group (p = 0.0001). Six of these eyes underwent PK again and all the grafts showed keratoconic changes histopathologically. The mean Ks during the whole observation period was 52.5 diopters (D) in the KC group and 49.2 D in the Others group (p < 0.0001). Logistic regression analysis revealed the risk factors of recurrent KC with positive Ks change and large CYL with significant p values (p = 0.0102, 0.0318, respectively).

Conclusions: KC progresses even after PK over the long term, requiring re-grafting in some cases. Risk factors for recurrent KC after PK are increasing Ks over time and a large CYL.