Fourier Analysis of Keratometric Data in Epithelium Removal versus Epithelial Disruption Corneal Cross-linking
Purpose: To compare epithelium-removal and epithelium-disruption corneal crosslinking (CXL) methods in Fourier analysis of keratometric data and clinical outcomes.
Methods: 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.
Results: 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 = ?). The corresponding figures were 433.50 ± 33.50 μm and 451.90 ± 39.70 μm, respectively, six months after the treatment (P = 0.0001). The irregularity component was 0.030 ± 0.016 μm in the epithelium-removal group and 0.028 ± 0.011 μm in the epithelium-disruption group preoperatively (P = ?). 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).
Conclusion: 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 within the six-month follow-up period.
Corneal Cross Linking, Epithelium Disruption, Epithelium Removal, Fourier Analysis, Keratoconus, Randomized Controlled Trial, Transepithelial
1. Rabinowitz YS. Keratoconus. Surv Ophthalmol 1998;42:297–319.
2. Rebenitsch RL, Kymes SM, Walline JJ, Gordon MO. The lifetime economic burden of keratoconus: a decision analysis using a Markov model. Am J Ophthalmol 2011;151:768–773.
3. Tatematsu-Ogawa Y, Yamada M, Kawashima M, Yamazaki Y, Bryce T, Tsubota K. The disease burden of keratoconus in patients’ lives: comparisons to a Japanese normative sample. Eye Contact Lens 2008;34:13–16.
4. Hashemi H, Khabazkhoob M, Fotouhi A. Topographic keratoconus is not rare in an Iranian population: the Tehran eye study. Ophthalmic Epidemiol 2013;20:385–391.
5. Wollensak G, Spoerl E, Seiler T. Riboflavin/ultraviolet a- induced collagen crosslinking for the treatment of keratoconus. Am J Ophthalmol 2003;135:620–627.
6. Li J, Ji P, Lin X. Efficacy of corneal collagen cross-linking for treatment of keratoconus: a meta-analysis of randomized controlled trials. PLOS ONE 2015;10:e0127079.
7. Sedaghat M, Bagheri M, Ghavami S, Bamdad S. Changes in corneal topography and biomechanical properties after collagen crosslinking for keratoconus: 1-year results. Middle East Afr J Ophthalmol 2015;22:212.
8. Lesniak SP, Hersh PS. Transepithelial corneal collagen crosslinking for keratoconus: six-month results. J Cataract Refract Surg 2014;40:1971–1979.
9. Li W, Wang B. Efficacy and safety of transepithelial corneal collagen crosslinking surgery versus standard corneal collagen crosslinking surgery for keratoconus: a meta-analysis of randomized controlled trials. BMC Ophthalmol 2017;17:262.
10. Soeters N, Wisse RP, Godefrooij DA, Imhof SM, Tahzib NG. Transepithelial versus epithelium-off corneal crosslinking for the treatment of progressive keratoconus: a randomized controlled trial. Am J Ophthalmol 2015;159:821–828.
11. Rechichi M, Daya S, Scorcia V, Meduri A, Scorcia G. Epithelial-disruption collagen crosslinking for keratoconus: one-year results. J Cataract Refract Surg 2013;39:1171–1178.
12. Hirji N, Sykakis E, Lam FC, Petrarca R, Hamada S, Lake D. Corneal collagen crosslinking for keratoconus or corneal ectasia without epithelial debridement. Eye 2015;29:764.
13. Hashemi H, Miraftab M, Hafezi F, Asgari S. Matched comparison study of total and partial epithelium removal in corneal cross-linking. J Refract Surg 2015;31:110–115.
14. Galvis V, Tello A, Carreño NI, Ortiz AI, Barrera R, Rodriguez CJ, et al. Corneal cross-linking (with a partial deepithelization) in keratoconus with five years of followup. Ophthalmol Eye Dis 2016; 8:17–21.
15. Sideroudi H, Labiris G, Ditzel F, Tsaragli E, Georgatzoglou K, Siganos H, et al. Validation of Fourier analysis of videokeratographic data. Int Ophthalmol 2018;38:1433– 1440.
16. Sideroudi H, Labiris G, Georgatzoglou K, Ditzel F, Siganos C, Kozobolis V. Fourier analysis of videokeratography data: clinical usefulness in grade I and subclinical keratoconus. J Cataract Refract Surg 2016;42:731–737.
17. Oshika T, Tanabe T, Tomidokoro A, Amano S. Progression of keratoconus assessed by Fourier analysis of videokeratography data. Ophthalmology 2002;109:339–342.
18. Greenstein SA, Hersh PS. Characteristics influencing outcomes of corneal collagen crosslinking for keratoconus and ectasia: implications for patient selection. J Cataract Refract Surg 2013;39:1133–1140.
19. Sloot F, Soeters N, van der Valk R, Tahzib NG. Effective corneal collagen crosslinking in advanced cases of progressive keratoconus. J Cataract Refract Surg 2013;39:1141–1145.
20. Greenstein SA, Shah VP, Fry KL, Hersh PS. Corneal thickness changes after corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results. J Cataract Refract Surg 2011;37:691–700.
21. Ziaei M, Meyer J, Gokul A, Vellara H, McGhee CN. Direct measurement of anterior corneal curvature changes attributable to epithelial removal in keratoconus. J Cataract Refract Surg 2018;44:71–77.
22. Godefrooij DA, El Kandoussi M, Soeters N, Wisse RP. Higher order optical aberrations and visual acuity in a randomized controlled trial comparing transepithelial versus epithelium-off corneal crosslinking for progressive keratoconus. Clin Ophthalmol 2017;11:1931.