Corneal Collagen Cross-Linking with and without Epithelial Removal: A Contralateral Study with 0.5% Hypotonic Riboflavin Solution

Abstract

Purpose. Our main purpose was to compare safety and efficacy in the treatment of progressive keratoconus with “epithelium-on” and “epithelium-off” corneal collagen cross-linking (CXL). Our secondary purpose was to evaluate efficacy of CXL when hypotonic 0.5% riboflavin is used as photosensitizer. Methods. One eye of 20 patients with bilateral progressive keratoconus was randomly treated for “epithelium-on” CXL (group 1) while the fellow eye underwent “epithelium-off” CXL (group 2). Hypotonic 0.5% riboflavin was used in both groups. Visual acuity, refraction, corneal topography, and wavefront aberrometry were evaluated at baseline and after 1, 6, and 12 months. Specular microscopy was performed on 10 patients preoperatively and after 12 months. Postoperative pain was evaluated using a patient questionnaire. Results. Uncorrected and corrected distance visual acuity improved significantly in both groups. Refraction, topography, and aberrometry showed nonsignificant changes from the preoperative status throughout the 12-month follow-up in both groups. Moreover, the outcomes between the groups were comparable at all follow-up points. Endothelial cell-count was stable. Postoperative pain length was shorter in group 1 (P < 0.001). Conclusion. “Epithelium-on” and “epithelium-off” CXL using hypotonic 0.5% riboflavin were equally safe and effective in stabilization of keratoconus. Topography and aberrometry outcomes in both groups failed to show any significant improvements. This study is registered at ClinicalTrials.gov: NCT01181219.

Presbyopic PiXL Cross-Linking

“…The intact epithelium prevents riboflavin penetration [45] (the large molecular weight of riboflavin being responsible for this). Even the use of higher-concentration (0.5 %) riboflavin solution through the intact epithelium may not facilitate improved results in comparison to the standard (0.1 %) concentration [46].…”

Efficacy and safety of transepithelial collagen crosslinking for progressive keratoconus

“…Studies comparing TE CXL with standard CXL using randomized control trials have shown improvement in both Kmax and BCVA in both protocols. However, the change and stabilization was observed more and prolonged in those treated with standard CXL 22. Since the results of both TE and standard CXL are comparable, TE CXL offers a trade-off between better safety profile and clinically acceptable efficacy.…”

Corneal Collagen Cross-linking Combined With Simulation of Femtosecond Laser–Assisted Refractive Lens Extraction

“…24,25 Even higher concentration (0.5%) riboflavin solutions may not facilitate improved results in comparison with the standard (0.1%) concentration. 26 The second issue is epithelial and Bowman membrane absorption/filtering of UV-A that could lead to lesser energy delivered to riboflavin-saturated stroma, as effective absorption by riboflavin at the superficial layers inhibits UV-A transmission. 27 Some studies indicate approximately onethird epithelial UV-A absorption, 24 whereas other studies suggest that human corneal epithelium and the underlying basement membrane absorb strongly only at wavelengths less than 310 nm.…”

“…30 There is thus inconclusive evidence in the peer-reviewed literature on the aspect of efficacy of some epithelium-on CXL variations. 3,8,26,31,32 The in situ riboflavin application naturally overcomes the first of the 2 obstacles, related to riboflavin penetration through the intact epithelium and in acting as a "blocking" agent against UV-A propagation. This is because the epithelium and Bowman layer, that the UV-A light has to transcend, are not soaked in riboflavin.…”