Factors associated with graft astigmatism after corneal transplantation for keratoconus

BACKGROUND: Graft astigmatism remains a major impediment to early visual rehabilitation and the long-term success of keratoplasty. Previous studies have identified graft size, donor–recipient size discrepancy, timing of suture removal, and surgical indication as factors associated with postoperative graft astigmatism. However, these studies often included heterogeneous corneal pathologies and evaluated the effects of only one or a limited number of variables. The present study aimed to investigate factors associated with corneal graft astigmatism following corneal transplantation in a large cohort of patients with keratoconus. METHODS: This retrospective, comparative interventional case series included 646 consecutive corneal transplants performed in 556 patients with keratoconus. Of these, 338 eyes underwent penetrating keratoplasty and 308 eyes underwent deep anterior lamellar keratoplasty. Postoperative keratometric astigmatism was assessed 3 to 12 months after complete suture removal. Generalized linear models were used to evaluate preoperative, intraoperative, and postoperative factors associated with postoperative keratometric astigmatism. RESULTS: The mean age at the time of keratoplasty was 29.3 ± 8.8 years. The mean postoperative keratometric astigmatism was 4.78 ± 2.24 D (range, 0.0–14.0 D). Increasing patient age (β = 0.05, P < 0.001) and a prior history of vernal keratoconjunctivitis (β = 0.49, P = 0.03) were significantly associated with greater postoperative keratometric astigmatism. Keratometric astigmatism was significantly higher in patients older than 30 years at the time of corneal transplantation. Deep anterior lamellar keratoplasty was associated with lower postoperative keratometric astigmatism during the second study period (β=−0.80, P = 0.008), when this technique was predominantly performed. Other variables, including keratoconus severity (P = 0.10), donor age (P = 0.10), graft rating (P = 0.37), donor trephine size (P = 0.27), donor–recipient disparity (P = 0.54), suturing technique (P = 0.88), selective suture removal (P = 0.07), duration of corticosteroid therapy (P = 0.70), time to complete suture removal (P = 0.30), and suture-related complications (P = 0.77), were not significantly associated with postoperative graft astigmatism. CONCLUSIONS: Age at the time of keratoplasty, a history of vernal keratoconjunctivitis, and possibly the keratoplasty technique were associated with postoperative graft astigmatism. Other intraoperative and postoperative variables were not significantly associated with keratometric astigmatism following corneal transplantation in patients with keratoconus.