Risk Factors for Failure of Keratoplasty in Keratoconus: Penetrating vs. Deep Anterior Lamellar Keratoplasty

Purpose: To determine the etiologic factors on rejection and failure rates and ocular surface changes after corneal transplantation by either DALK or PKP, in cases of keratoconus (KCN). Methods: In this cross-sectional study, considering the existing data, patients with keratoconus referring to Labbafinejad Medical Center from 2006 to 2016, who underwent corneal transplantation, were enrolled and recalled in this study. The diagnosis of Keratoconus was based on Slit lamp clinical findings, topographic, and tomographic findings, for which keratoplasty was indicated. All surgical procedures for corneal transplantation, as well as postoperative follow-up protocol, were identical. During the postoperative follow-up, a careful examination was performed on the complications and symptoms of corneal graft rejection and underlying causes. Results: In this study, 108 patients in each group (N= 216) were examined for at least 6 months after the removal of all sutures. The rate of graft rejection was 13% and 34.3% in the DALK and PKP groups, respectively (P<0.001). The failure rate was 7.4% and 2.8% in the DALK and PKP groups, respectively (P = 0.12). Generally, 60.5% of all cases of corneal vascularization developed rejection (23 out of 38) (P<0.001). The rate of graft opacity was 30.6% in the DALK group while it was 14.8% in the PKP group (P = 0.006). Patients with dry eye, graft ulcer, and stitch abscess were more likely to develop rejection (P<0.001). Gender, age of host and donor, method of Donor preservation, duration of surgery, duration of follow-up, postop duration of topical corticosteroid administration, the season of graft rejection, Infiltration, history of previous rejection, time suture removal, history of VKC, and history of corneal transplantation in the other eye were not correlated to rejection. Conclusion: Ocular surface changes and dry eye is more prevalent in DALK in relation to PKP. Corneal vascularization, which is an important factor in graft rejection, occurs more frequent in PKP than DALK. Opacification of graft interface, which occurs in DALK, is an important factor in graft failure.