Improvement of molecular photoactivation technology and broadened clinical applications

Le cross-linking du collagène (CXL) consiste à photoactiver de la riboflavine à l'aide d'UVA afin de générer une réaction chimique qui augmente la résistance biomécanique de la cornée. Ce travail étudie le type de réaction chimique responsable de la modification biomécanique du CXL ainsi que son effet bactéricide pour le traitement des kératites bactériennes. Pour ce faire, nous avons étudié les modifications biomécaniques de la cornée ainsi que l'effet bactéricide du CXL sous différentes conditions. Notre étude montre que la modification biomécanique du CXL est totalement oxygène dépendant alors que l'effet bactéricide du CXL est probablement composé de deux mécanismes : oxygène dépendant et oxygène indépendant. Ceci laisse penser que la riboflavine photoactivée est bactéricide sans génération de radicaux libres mais via son interaction avec un élément essentiel de la bactérie, probablement l'ADN

PACK-CXL: Corneal cross-linking for treatment of infectious keratitis

This article discusses corneal cross-linking (CXL) and how it transitioned from a modality for treating corneal ectatic disorders to an inventive means of treating infectious keratitis. Initially, CXL was successfully developed to halt the progression of ectatic diseases such as keratoconus, using the standard Dresden protocol. Later, indications were extended to treat iatrogenic ectasia developing after laser-assisted in situ keratomileusis (LASIK) and photo-refractive keratectomy (PRK). At the time, it had been postulated that the combination of ultraviolet light with riboflavin could not only biomechanically strengthen the cornea but also was capable of destroying living cells and organisms including keratocytes and pathogens. Thus a new and innovative concept of treatment for infectious keratitis emerged through the use of CXL technology. Initially only advanced infectious melting ulcers resisting standard microbicidal therapy were treated with CXL in addition to standard therapy. In subsequent studies CXL was also used to treat bacterial keratitis as first line therapy without the use of concomitant antibiotic therapy. With the increasing interest in CXL technology to treat infectious keratitis and to clearly separate its use from the treatment of ectatic disorders, a new term was adopted at the 9 th CXL congress in Dublin for this specific indication: PACK-CXL (photoactivated chromophore for infectious keratitis). PACK-CXL has the potential to eventually become an interesting alternative to standard antibiotic therapy in treating infectious corneal disorders, and may help reduce the global burden of microbial resistance to antibiotics and other therapeutic agents

Corneal Collagen Cross-Linking for Ectasia after LASIK and Photorefractive Keratectomy

Purpose: To report the long-term results of corneal collagen cross-linking (CXL) in ectasia after LASIK and photorefractive keratectomy (PRK). Design: Retrospective, interventional cases series. Participants: Twenty-six eyes of 26 patients (18 male, 8 female) with postoperative ectasia after LASIK (23 eyes) and PRK (3 eyes) were included with a mean age of 35 ± 9 years at the time of treatment and a mean follow-up of 25 months (range, 12-62 months). Methods: All consecutive patients treated with CXL for progressive ectasia after LASIK or PRK at the Institute for Refractive and Ophthalmic Surgery, Zurich, Switzerland between 2004 and 2010 were included. Main outcome measures: Corrected distance visual acuity (CDVA), maximum keratometry readings (K(max)), minimum radius of curvature (R(min)), and 6 corneal topography indices were assessed in this study. Results: Mean CDVA before CXL was 0.5 logarithm of the minimum angle of resolution (logMAR) units, which improved to a mean of 0.3 logMAR units (P&lt;0.001). Corrected distance visual acuity improved 1 line or more in 19 cases and remained unchanged in 7 patients. Mean K(max) after CXL of 50.9 ± 4.9 diopters (D) was significantly lower (P&lt;0.001) than mean pre-CXL K(max) of 52.8 ± 5 D. The R(min) after CXL was increased significantly (P = 0.006), whereas the index of surface variance (P = 0.03), the index of vertical asymmetry (P = 0.04), the keratoconus index (P = 0.03), and the central keratoconus index (P = 0.016) were reduced significantly. Conclusions: Ectasia after LASIK and PRK was arrested by CXL with stabilization or improvement of CDVA and K(max) after a mean follow-up of 25 months. There were improvements in 4 topography indices, suggesting a more regular corneal surface.</p