Corneal stromal demarcation line after 4 protocols of corneal crosslinking in keratoconus determined with anterior segment optical coherence tomography

Purpose: To use anterior segment optical coherence tomography (AS-OCT) to compare corneal stromal demarcation line depth after 4 treatment protocols of corneal crosslinking (CXL). Setting: Eye Clinic, Sapienza University of Rome, Terracina (Latina), Italy. Design: Prospective case series. Methods: Patients with progressive keratoconus were delegated to one of the following CXL treatments: (1) conventional epithelium (epi)-off 3 mW/cm2according to the standard Dresden protocol (C-CXL group), (2) accelerated epi-off 10 mW/cm2(A-CXL group), (3) transepithelial epi-on 3 mW/cm2(TE-CXL group), or (4) transepithelial epi-on by iontophoresis 10 mW/cm2(I-CXL group). Two independent observers measured the corneal stromal demarcation line using AS-OCT. Results: The study comprised 70 patients (120 eyes, 30 eyes in each group). The corneal stromal demarcation line was identified on AS-OCT scans in 109 eyes (90.8%). One month after the treatment, the mean stromal demarcation line depth was 275.05 μm ± 41.83 (SD) in the C-CXL group, 279.35 ± 33.07 μm in the A-CXL group, 132.60 ± 22.14 μm in the TE-CXL group, and 235.40 ± 37.08 μm in the I-CXL group. The difference in stromal demarcation line depth was not statistically significant between the C-CXL and A-CXL group, but it was statistically significant (P <.05) between the epi-off and epi-on CXL groups and between the 2 epi-on groups, where the demarcation line was significantly deeper in the I-CXL group than in the TE-CXL group. Conclusion: The corneal stromal demarcation line was significantly deeper after epi-off 30-minute standard CXL treatment and after epi-off 9-minute accelerated CXL with high-intensity ultraviolet-A irradiation.