Keratoconus and crosslinking: pharmacokinetic considerations

Customized Topography-Guided Corneal Collagen Cross-linking for Keratoconus

PURPOSE

To compare the efficacy and safety of topography-guided corneal collagen cross-linking (TG-CXL) to conventional corneal CXL (C-CXL) in progressive keratoconus.

METHODS

In this prospective, nonrandomized clinical trial, 60 eyes of 60 patients were scheduled to receive either TG-CXL (30 eyes with deepithelialization focused on the cone, riboflavin application for 10 minutes, and 30 mW/cm² pulsed ultraviolet-A irradiance pattern according to topography) or C-CXL (30 eyes treated in accordance with the Dresden protocol). Patients were observed for 1 year postoperatively. Maximum keratometry (Kmax), mean keratometry in the inferior part of the cornea (I index), corrected distance visual acuity (CDVA), demarcation line observed in optical coherence tomography, and nerves and cell densities analyzed by confocal microscopy were compared preoperatively and at 1 year postoperatively.

RESULTS

The difference was significant for both Kmax (P < .01) and I index (P < .01) between the two groups. CDVA improved significantly in the TG-CXL (0.2162 ± 0.2495 logMAR, P < .05) versus the C-CXL (0.2648 ± 0.2574 logMAR, P = .104) group. A stromal demarcation line was observed in both treatment groups, with similar depth at the top of the cone (P = .391), but it was shallower at the surrounding area in the TG-CXL group (P < .0001). Stromal evaluation by confocal microscopy showed less damage and faster healing in the surrounding area than on the cone area in the TG-CXL group.

CONCLUSIONS

At 1 year postoperatively, TG-CXL seems to be as safe as C-CXL with stronger flattening in Kmax and I index and better improvement in CDVA. TG-CXL induces a biological gradient between the cone and the surrounding area that facilitates nerve and cell recovery. [J Refract Surg. 2017;33(5):290-297.].

Transepithelial Corneal Cross-linking Using an Enhanced Riboflavin Solution

PURPOSE

To assess the efficacy of a modified high concentration riboflavin solution containing benzalkonium chloride 0.01% for transepithelial corneal cross-linking (CXL).

METHODS

In this prospective, interventional multicenter cohort study, 26 eyes of 26 patients with documented progressive keratoconus who underwent transepithelial CXL were included. Follow-up at 6 and 12 months postoperatively included slit-lamp examination, uncorrected and corrected distance visual acuity (logMAR), maximum keratometry (Kmax), and corneal pachymetry (corneal thinnest point) as determined by Scheimpflug imaging. Statistical analysis was performed using repeated measures analysis of variance and the Friedman test for parametric and non-parametric data, respectively. P values less than .05 were considered significant.

RESULTS

Kmax did not change significantly at postoperative months 6 and 12. Changes in corneal thinnest point did not change postoperatively over 12 months. Uncorrected and corrected distance visual acuity did not change postoperatively. Progression (defined by an increase in Kmax greater than 1.00 diopter occurred in 46% of eyes at 12 months. Corneal epithelial defects were observed in 46% of the patients and marked punctate corneal epitheliopathy/loose epithelium in 23% of the patients in the immediate postoperative period. No corneal infection, sterile infiltrates, or haze were observed.

CONCLUSIONS

Transepithelial CXL with an enhanced riboflavin solution did not effectively halt progression of keratoconus. Significant epithelium damage was evident in the immediate postoperative period. [J Refract Surg. 2016;32(6):372-377.].