Pulsed vs continuous light accelerated corneal collagen crosslinking: in vivo qualitative investigation by confocal microscopy and corneal OCT

Abstract

Purpose To assess qualitative corneal changes and penetration of pulsed and continuous light accelerated crosslinking by in vivo confocal microscopy and corneal OCT. Methods A total of 20 patients affected from progressive keratoconus were enrolled in the study. Ten eyes of 10 patients underwent an epithelium-off pulsed-light accelerated corneal collagen crosslinking (PL-ACXL) by the KXL UV-A source (Avedro Inc.) with 8 min (1 s on/1 s off) of UV-A exposure at 30 mW/cm 2 and energy dose of 7.2 J/cm 2 ; 10 eyes of 10 patients underwent an epitheliumoff continuous-light accelerated corneal collagen crosslinking (CL-ACXL) at 30 mW/cm 2 for 4 min. Riboflavin 0.1% dextran-free plus hydroxyl-propyl-methylcellulose solution (VibeX Rapid, Avedro Inc.) was used for a 10-min corneal soaking. Treated eyes were examined by in vivo scanning laser confocal analysis and spectral anterior segment OCT at 1, 3, and 6 months. Results Epithelial stratification and nerves regeneration improved in time, being complete at month 6 in both groups without endothelial damage. Keratocyte apoptosis in PL-ACXL was estimated at a mean depth of B200 mm, whereas an uneven demarcation line was detectable by confocal microscopy at a mean depth of 160 mm in CL-ACXL. Conclusion In vivo confocal microscopy and corneal OCT allowed a precise qualitative analysis of the cornea after epithelium-off PL-ACXL and CL-ACXL treatments. Apoptotic effect was higher in pulsed than in continuous light treatments, exceeding 200 mm in corneal stroma. According to different morphological data, the clinical efficacy of ACXL needs to be determined in a long-term follow-up and large cohort of patients.

Clinical Outcomes at 1 Year following Corneal Ectasia Treatment with Accelerated Transepithelial Cross-linking

“…This is consistent with the findings reported in other series evaluating the results of transepithelial CXL, either by iontophoresis or accelerated. [19][20][21][22][23][24][25][26][27] Similarly, in line with all previous studies on transepithelial CXL, 19-27 a significant improvement in CDVA was observed after surgery that remained throughout the entire 12-month follow-up period. Lesniak and Hersh,24 in a prospective study, evaluated a similar technique and found a mean improvement in CDVA of 0.83 Snellen lines.…”

“…Other studies have evaluated changes in the maximum keratometry after different modalities of transepithelial CXL. [19][20][21][22][23][24][25][26][27] Lesniak and Hersh 24 found a mean reduction of 0.9D in the maximum keratometry in a prospective study that evaluated the results of a similar CXL technique than that used in our study over a 6-month period. It should be borne in mind that this study included keratoconus cases that were more advanced than in our series, so the mean keratometry was higher.…”

“…[14][15][16] For this reason, new CXL protocols are being developed in order to avoid having to debride the corneal epithelium, such as the creation of intrastromal pockets for riboflavin infusion 17,18 or transepithelial CXL, either iontophoresis-assisted or using a benzalkonium chloride solution to increase the permeability of the corneal epithelium. [19][20][21][22][23][24][25][26][27] Although there is some experimental and clinical evidence of the effectiveness of accelerated transepithelial CXL, it is still limited. The aim of the present prospective, noncomparative study was to assess the visual, refractive, topographic, and aberrometric changes in the ectatic corneas after accelerated transepithelial CXL over 1 year of follow-up.…”

In Vivo Confocal Microscopy after Corneal Collagen Crosslinking

“…5,26 2) 20 underwent high-fluence epithelium-off accelerated crosslinking (ACXL) at 30mW/cm 2 (10 eyes with pulsed light and 10 eyes with continuous light UV-A exposure). 15,16 3) 10 underwent transepithelial crosslinking (TE-CXL) at 3mw/cm 2 . 36 4) 10 underwent transepithelial accelerated crosslinking (TE-ACXL) at 45 mW/cm 2 .…”

Establishing Corneal Cross-Linking With Riboflavin and UV-A in the Mouse Cornea In Vivo: Biomechanical Analysis

“…12 However, clinical and experimental evidence did not show significant differences between the pulsed and standard CXL protocol. [13][14][15] These unsuccessful implementations show that there is a need for a better understanding of the cellular and molecular events occurring during CXL.…”