Das UV-/Riboflavin-Crosslinking der Hornhaut besitzt einen festen Stellenwert bei der Therapie progressiver Keratektasien. Die Therapie ist durch eine lange Behandlungsdauer (60 min nach dem ursprünglichen Dresdner Protokoll) und postoperative Schmerzen durch die für die Penetration des Riboflavins notwendige Abrasio gekennzeichnet. Umso verständlicher ist das Bestreben, die Belastung und auch die Gefahr für Komplikationen durch kürzere Bestrahlungsintervalle bzw. durch Belassen des Hornhaut-Epithels zu reduzieren. Angesichts des Problems, dass Riboflavin durch intaktes Hornhaut-Epithel nicht in das Hornhaut-Stroma penetrieren kann, wird versucht, durch die Gabe von Substanzen wie Ethylendiamintetraessigsäure (EDTA) oder Benzalkoniumchlorid die Penetration zu verbessern. Laborexperimentell sind diese Versuche der konventionellen Applikation nach Entfernung des Hornhaut-Epithels (Epi-off) deutlich unterlegen. Die 2 angeführten Studien bestätigen diese Ergebnisse nun auch durch prospektive und kontrollierte klinische Untersuchungen über 1 bzw. 3 Jahre. Ohne Abrasio kam es sowohl unter EDTA- als auch unter Benzalkoniumchlorid-Applikation bei einem nicht unerheblichen Teil der Patienten sogar zu einer weiteren Progression des Keratokonus, wohingegen bei den Epi-off-Kontrollgruppen keine Progression bzw. im Mittel eine deutliche Verbesserung (Reduktion) der maximalen Keratometerwerte erreicht werden konnte. Es bleibt abzuwarten, ob weitere Modifikationen (veränderte Zusammensetzung der Riboflavin-Lösung bzw. höhere Bestrahlungsdosis wegen der Filterfunktion des Epithels) die Penetration des Riboflavins bzw. den klinischen Effekt der Behandlung verbessern können, um einen der Standardbehandlung gleichwertigen Effekt zu erzielen. Außerhalb von Studien sollte das Epithel für die Crosslinking-Behandlung momentan jedoch entfernt werden.

Al Fayez MF, Alfayez S, Alfayez Y: Transepithelial Versus Epithelium-Off Corneal Collagen Cross-Linking for Progressive Keratoconus: A Prospective Randomized Controlled Trial. Cornea 2015;34(Suppl 10):S53-S56.

Purpose: To compare the safety and efficacy of transepithelial with epithelium-off corneal cross-linking for progressive keratoconus.

Methods: In a prospective clinical trial, 70 patients with progressive keratoconus were randomized to undergo corneal cross-linking with intact epithelium (n = 34) or after deepithelialization (n = 36). The main outcome measure was a change in the maximum K reading (Kmax).

Results: With 3-year follow-up, Kmax decreased in the epithelium-off group with a mean of 2.4 D and no patient showed evidence of progression. In the transepithelial group, Kmax increased by a mean of 1.1 D, and 20 patients (55%) showed progression of keratoconus.

Conclusions: In this study, epithelium-off was significantly more effective than transepithelial corneal cross-linking in halting the progression of keratoconus (P < 0.0001).

Soeters N, Wisse RP, Godefrooij DA, Imhof SM, Tahzib NG: Transepithelial versus epithelium-off corneal cross-linking for the treatment of progressive keratoconus: a randomized controlled trial. Am J Ophthalmol 2015;159:821-828.e3.

Purpose: To compare the clinical effects and safety of transepithelial corneal cross-linking (CXL) to epithelium-off (epi-off) CXL in progressive keratoconus.

Design: Randomized clinical trial (noninferiority).

Methods: Patients received either transepithelial CXL with Ricrolin TE (n = 35) or epi-off CXL with isotonic riboflavin (n = 26) in 1 academic treatment center, using a simple unrestricted randomization procedure. The main outcome measure was clinical stabilization of keratoconus after 1 year, defined as a maximal keratometry (Kmax) increase <1 diopter (D).

Results: Average Kmax was stable at all visits in the transepithelial group, while after epi-off CXL a significant flattening of 1.2-1.5 D was demonstrated from the 3-month follow-up onwards. The trend over time in Kmax flattening was significantly different between the groups (P = .022). Eight eyes (23%) in the transepithelial group showed a Kmax increase of >1 D after 1 year (range 1.3-5.4 D) vs none in the epi-off group (P = .017). There was significant different trend in corrected distance visual acuity (CDVA), with a more favorable outcome in the transepithelial group (P = .023). In the transepithelial group, no complications occurred and in the epi-off group, 4 eyes (15%) developed complications owing to healing problems (sterile infiltrate, herpes keratitis, central haze, and stromal scar).

Conclusion: This study showed that although transepithelial CXL was a safe procedure without epithelial healing problems, 23% of cases showed a continued keratoconus progression after 1 year. Therefore, at this time, we do not recommend replacing epi-off CXL by transepithelial CXL for treatment of progressive keratoconus.

2016
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