Association Between Corneal Epithelial Thickness, Higher-Order Aberrations and Contrast Sensitivity in Refractive Surgery Candidates

Purpose: To report the relationship between changes in the thickness of the corneal epithelium at its apex (epithelial thickness peak, ET peak) and alterations in Contrast Sensitivity (CS) and Higher-Order Aberrations (HOAs) following Photorefractive Keratectomy (PRK) and Laser-Assisted In Situ Keratomileusis (LASIK). Methods: A retrospective analysis was conducted on data from 58 eyes that underwent LASIK and 60 eyes that underwent PRK. Measurements of Corrected Distance Visual Acuity (CDVA), Weber contrast (SC WEBER), logarithm of CS (CS LOGS), ET peak, Low-Order Aberrations (LOAs) and HOAs were obtained before and after surgery (mean follow-up: 12.18 ± 1.48 months). Statistical correlations between the changes in these parameters were analyzed. Results: Significant postoperative changes were observed in CS, ET peak and HOAs in both surgical groups. In the PRK group, a mean increase of 6.62 ± 1.31 μm in ET peak showed a significant correlation with a reduction in CS and changes in specific LOAs (Z00, Z02, Z11) and HOAs (Z31, Z42). Conversely, in the LASIK group, despite a similar average increase in ET peak (6.55 ± 1.26 μm), no significant correlation was found with CS reduction or changes in HOAs, although correlations with LOAs (Z00, Z02, Z11) were present. Changes in ET peak did not correlate with CDVA in either group. Conclusion: While both photorefractive keratectomy and laser-assisted in situ keratomileusis resulted in comparable postoperative increases in central corneal epithelial thickness, these changes were significantly linked to decreased contrast sensitivity after photorefractive keratectomy but not after Laser-Assisted In Situ Keratomileusis. This difference might be due to variations in the ablation profile and the corneal healing process between the two techniques. The findings suggest that epithelial remodeling has a different impact on visual function depending on the type of refractive surgery performed.