Comparing outcomes of penetrating keratoplasty versus deep anterior lamellar keratoplasty for keratoconus: a systematic review and meta-analysis

Keratoconus is a progressive corneal ectasia that can lead to visual impairment. Penetrating keratoplasty (PK) has traditionally been the standard surgical intervention. However, deep anterior lamellar keratoplasty (DALK) has emerged as a potential alternative with fewer postoperative complications due to preservation of the patient's endothelium. The comparative efficacy of PK versus DALK remains debated. This systematic review and meta-analysis followed PRISMA 2020 guidelines. Medline (via PubMed) and Google Scholar were searched from inception to November 2024 for randomized controlled trials and observational studies comparing PK and DALK in keratoconus patients. Twenty-seven studies involving 2,152 patients (PK: 1,105; DALK: 1,047) were included. Primary outcomes assessed included best-corrected visual acuity (BCVA), spherical equivalent (SE), refractive cylinder (RC), topography cylinder (TC), graft rejection episodes (GRE), and overall complications. Study quality was evaluated using the National Institutes of Health (NIH) and the Revised Cochrane Risk of Bias (RoB 2) tool for randomized trials. There were no significant differences between PK and DALK in BCVA (MD = -0.00; p-value=0.92), RC (MD = 0.28; p-value=0.26), or TC (MD = 0.15; p-value=0.46). DALK showed a significantly higher SE (MD = 0.97; p