Corneal stromal demarcation line after accelerated crosslinking using continuous and pulsed light

Purpose - To evaluate and compare the depth of corneal stromal demarcation line after accelerated collagen crosslinking (CXL) using continuous and pulsed light ultraviolet-A (UVA) exposure. Setting Department of Ophthalmology, Arcispedale Santa Maria Nuova, Reggio Emilia, Italy. Design Retrospective case series. Methods Patients with progressive keratoconus were assigned to 1 of 2 treatment protocols using the same irradiation device for accelerated CXL. Patients assigned to Group A received accelerated CXL using continuous UVA light exposure at 30 mW/cm2 for 4 minutes. Patients assigned to Group B received accelerated CXL using pulsed UVA light with 8 minutes (1 second on/1 second off) of UVA exposure at 30 mW/cm2 and energy dose of 7.2 J/cm2. One month after surgery, corneal stromal demarcation line depth was measured by 2 independent observers using anterior segment optical coherence tomography (AS-OCT). Results A total of 60 patients were assessed. Corneal stromal demarcation line was easily identified on AS-OCT scans in all eyes by both observers. The mean depth of stromal demarcation line was 149.32 ± 36.03 μm in Group A and 213 ± 47.38 μm in Group B. The difference in stromal demarcation line depth between groups was statistically significant (P < .001). Conclusions Using accelerated CXL, the corneal stromal demarcation line was significantly deeper using pulsed rather than continuous light exposure.