Deep anterior lamellar keratoplasty versus automated lamellar therapeutic keratoplasty for keratoconus: comparison of postoperative corneal higher-order aberrations

Purpose: To compare the corneal higher-order aberrations (HOAs) measurements amongst the following groups of subjects: keratoconus (KC) patients; KC patients after penetrating keratoplasty (PK) or deep-anterior-lamellar-keratoplasty (DALK) or automated-lamellar-therapeutic-keratoplasty (ALTK); and, age-matched controls with normal corneas. Methods: This retrospective, observational, cross-sectional study included one eye of the following subjects: 40 patients with KC; 23 KC patients after PK; 17 KC patients after DALK; 18 KC patients after ALTK; and 38 controls. All subjects underwent imaging with a rotating Scheimpflug camera to assess the HOAs from the anterior (ACS) and posterior corneal surface (PCS) within the central 4-mm and 6-mm zones. The conversion of the corneal elevation profile into corneal wave-front data was performed using the Zernike polynomials. Total, 3rd and 4th order HOAs were considered. The root mean square of the Zernike vector magnitude, expressed in µm, was used for the analysis. Differences amongst groups were assessed using the Kruskal-Wallis and least significant difference (LSD) tests. Statistical significance was defined as p<0.05. Results: The total HOAs from both corneal surfaces were significantly lower in controls than in the other groups (p<0.001). Considering the 3rd and 4th order aberrations due to the ACS, the PK group showed significantly higher trifoil, whereas the KC and ALTK groups showed significantly higher coma in comparison with the other groups (p<0.01). Considering the 3rd and 4th order aberrations from the PCS, coma appeared significantly higher in KC, DALK and ALTK groups in comparison with controls and PK eyes (p<0.01). Conclusions: The HOAs due to both corneal surfaces appeared comparable between DALK and ALTK eyes, except for coma from the ACS, which was significantly higher after ALTK, indicating a higher irregularity of the central anterior corneal profile. These results may be due to a dishomogeneous residual recipient stromal bed after ALTK compared with DALK, which tends to be thinner in the paracentral region and thicker in the periphery after ALTK.