New CXL Technique

New transepithelium CXL technique shows efficacy similar to Epi-off Dresden protocol CXL. Roibeárd O’hÉineacháin reports. A new transepithelial corneal cross-linking (CXL) technique called Boost Epi-on CXL that involves supplemental oxygen appears to provide the same depth and volume of treatment as standard epi-off crosslinking, according to a study by Clinical Associate Professor Lim Li MBBS, M Med (Ophth), FRCS(Ed), FAMS. “The corneal stromal demarcation line depth achieved with this technique is comparable to standard Dresden protocol epithelialoff corneal cross-linking and had a similar safety profile. It also has the added advantage of faster recovery and improved patient comfort compared to conventional cross-linking,” Prof Lim said. The retrospective study included 25 eyes of 25 progressive keratoconus patients who underwent transepithelial CXL with supplemental oxygen between December 2019 and January 2021. The patients had a mean age of 28.3 years, a mean preoperative K1 of 45.9 D, a mean K2 of 50.2 D, and a mean Kmax of 57.5 D. Anterior segment optical coherence tomography (AS-OCT) showed the mean post-treatment corneal stromal demarcation line was 367.3 μm ± 20.1 μm. The volume of treated cornea including and excluding the central corneal epithelial thickness was 73.3% and 70.4%, respectively. There was no reduction in endothelial cell count (ECC) post-procedure. Adverse events included mild corneal haze in eight eyes (32.0%) and one case of peripheral stromal infiltrate that resolved with topical broad-spectrum antimicrobial treatment. COMPARABLE TO STANDARD EPI-OFF CXL Studies with epi-off CXL show that it is a safe and effective procedure for keratoconus since it halts keratoconus progression and improves topographic and visual parameters. However, it can cause considerable postoperative pain. Epitheliumon procedures provide improved patient comfort and faster recovery and may reduce the risk of infection. But they also have a shallower treatment effect, result in less corneal flattening, and are less effective in preventing progression. “The barrier function of the corneal epithelium may limit the availability of all three key components of crosslinking: Riboflavin, UVA, Oxygen,” Prof Lim said. The Boost Epi-on procedure addresses all three of those drawbacks. First, it uses a higher, 0.25% concentration of riboflavin together with benzalkonium chloride to increase penetration through the epithelium. Second, it uses a higher intensity of UVA, irradiating the central 9.0 mm of the cornea 30 mW/cm² of UVA light, pulsed at one-second intervals for 11 minutes and six seconds, giving total energy of 10 J/cm². Third, during the corneal irradiation, patients wear special goggles infused with oxygen at a concentration of 90%. Following the procedure, patients received a bandage contact lens; a one-month regimen of topical moxifloxacin, preservative-free artificial tear eyedrops, and Loteprednol etabonate eyedrops; and a one-week regimen of oral etoricoxib. She noted in the present study, the depth of the corneal demarcation line was roughly equivalent to that achieved with standard Dresden Protocol Epi-on CXL and about two to three times that achieved with standard transepithelial CXL. “Further prospective studies are required to refine treatment parameters and validate the safety and efficacy of the procedure,” Prof Lim concluded. This presentation was made at the 39th Congress of the ESCRS in Amsterdam. Prof Lim Li is a Senior Consultant of the Corneal & External Eye Disease Department at the Singapore National Eye Centre (SNEC). lim.li@singhealth.com.sg