Continuous-light versus pulsed-light accelerated corneal crosslinking with ultraviolet-A and riboflavin

To determine whether the pulsed-light ultraviolet-A (UVA) accelerated corneal crosslinking (CXL) procedure is more efficacious and selective than its continuous-light counterpart in rabbits.

School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China.

Experimental study.

Fifty-four rabbits were divided into 2 groups. Group 1 had continuous-light accelerated CXL using 9 mW/cm² UVA for 10 minutes (5.4 J/cm²). Group 2 had pulsed-light accelerated CXL by exposing them to 9 mW/cm² UVA for 20 minutes (1 second on/1 second off). Corneal stromal demarcation line depth, in vivo confocal microscopic analysis, biomechanical stiffness, endothelial cell density, and keratocyte apoptosis were measured after performing these CXL procedures.

The mean stromal demarcation line depth was 254.7 μm ± 47.4 (SD) in Group 1 and 341.1 ± 36.1 μm in Group 2 (P < .01). One day after CXL, confocal analysis and histological staining identified keratocyte apoptotic fragments in the anterior stroma in the Group 2 corneas whereas all cells were obliterated in Group1. Seven days after treatment, the thicknesses in Group 1 were significantly greater than those in Group 2 (P < .05). Endothelial cell losses were reversible; however, in Group 1, some losses were still evident on day 7. Increases in both the stress-strain relationship and tangent modulus in Group 2 were greater than those in Group 1.

The pulsed-light accelerated CXL protocol was less injurious and more efficacious at inducing CXL than the continuous-light accelerated CXL protocol in rabbit corneas.