Fourier Analysis of Keratometric Data in Epithelium Removal versus Epithelial Disruption Corneal Cross-linking

To compare epithelium-removal and epithelium-disruption corneal crosslinking (CXL) methods in Fourier analysis of keratometric data and clinical outcomes.

In this double masked randomized clinical trial, each eye of 34 patients with bilateral keratoconus was randomly allocated to either the epithelium-removal or epithelium-disruption CXL treatment groups. Ocular examination, refraction, uncorrected and best spectacle-corrected visual acuity (UCVA and BSCVA, respectively) measurements, and Pentacam imaging (keratometry, pachymetry, and Fourier analysis) were performed at baseline and at six-month follow-up period.

Patients' mean age was 23.3 $$ 3.6 years. The preoperative thickness of the thinnest point was 459.20 $$ 37.40 µm and 455.80 $$ 32.70 µm in the epithelium-removal and epithelial-disruption CXL groups, respectively (P > 0.05). The corresponding figures were 433.50 $$ 33.50 µm and 451.90 $$ 39.70 µm, respectively, six months after the treatment (P = 0.0001). Irregularity component of the fourier analysis was 0.030 $$ 0.016 µm in the epithelium-removal group and 0.028 $$ 0.011 µm in the epithelium-disruption group preoperatively (P > 0.05). This measurement was 0.031 $$ 0.016 µm and 0.024 $$ 0.009 µm, respectively at month 6 (P = 0.04). The epithelium-disruption CXL group had better results in terms of the thickness of the thinnest point and the irregularity component as compared to the epithelium-removal group. The two study groups were comparable in spherical equivalent, mean keratometry, UCVA, BSCVA, or other Fourier analysis components (spherical R min, spherical eccentricity, central, peripheral regular astigmatism, and maximum decentration) (P $$ 0.05).

This study shows that epithelium-disruption CXL is superior to epithelium-removal CXL regarding the short-term changes in pachymetry and corneal irregularity. Other evaluated parameters were comparable between the two techniques.