Penetrating Keratoplasty versus Deep Anterior Lamellar Keratoplasty for Keratoconus: A Systematic Review and Meta-Analysis of 27,018 Eyes

Keratoconus is a bilateral asymmetrical degeneration in the cornea. It is associated with local thinning in the cornea leading to visual problems such as myopia and astigmatism. Several treatments, such as lenses and keratoplasty surgeries, were utilized to treat this condition. In this study, we aim to compare deep anterior lamellar keratoplasty (DALK) to penetrating keratoplasty (PK). We registered our study protocol on PROSPERO (CRD42024559427). Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched four electronic databases (PubMed, Scopus, Cochrane Library, and Web of Science) to identify eligible studies reported up to June 2024. Using STATA 17, we reported outcomes as risk ratios (RRs) or mean difference (MD) and confidence intervals (CIs). A P-value ≤.05 is considered as statistically significant. The meta-analysis included a total of 47 studies with a total number of 27,018 eyes. There was no significant difference between PK and DALK in terms of best-corrected visual acuity (BCVA) at 1 year (Hedge’s g: 0.03 with 95% CI [−0.13, 0.19], p = .71). PK was associated with a lower risk of graft failure than DALK (log RR: −0.41 with 95% CI [−0.74, −0.08], p = .01). PK was associated with a higher risk of graft rejection than DALK (log RR: 0.85 with 95% CI [0.35, 1.35], p p = .82). The visual outcomes such as BCVA, astigmatism, and spherical equivalent refraction, of PK and DALK are comparable. However, PK was associated with a higher risk of complications and rejection episodes, but, a lower risk of graft failure.