Epithelium-On Versus Epithelium-Off Corneal Collagen Cross-Linking for The Management of Keratoconus

Background: Keratoconus is a noninflammatory, bilateral, frequently asymmetrical, and most common corneal ectatic disorder characterized by central corneal thinning, biomechanical weakening, and steepening of the corneal curvatures leading to substantial distortion of vision. The estimated prevalence worldwide is 54.5 cases/100,000. Objective: The aim of the work was to compare epithelium-on and epithelium-off corneal collagen cross-linking for the management of keratoconus as regards keratoconus progression and visual outcome. Patients and methods: In this study, 20 eyes of 11 keratoconus patient were included. All were having keratoconus and presented with diminution of vision, increasing myopia and / or astigmatism. Cases with corneal scarring, corneal thickness less than 400 μm at the thinnest point and active corneal infections were excluded. The preoperative evaluation of patients showed UCVA, In epithelium-on (group 1) ranging from 0.05 to 0.60 with a mean 0.29 ± 0.21 and in epithelium-off (group 2) UCVA ranging from 0.05 to 0.50 with a mean 0.23 ± 0.13. Results: The postoperative results revealed improvement of UCDVA and BSCVA at 6 month postoperative in both groups. The postoperative manifest refraction spherical equivalent showed stability with mild improvement in both groups. Keratometric readings showed a decrease in curvature in both groups in the follow up period. Corneal hysteresis (CH) and corneal resistance factor (CRF) showed no significant difference after 6 months of follow up. Conclusion: It could be concluded that UVA/Riboflavin cross-linking of ectatic cornea by its two techniques is effective, safe, stable and do not affect corneal biomechanical characteristics, that leads in the majority of the cases to a halt the progression of ectasia.