Near-infrared light-induced transcranial photobiomodulation enhances the visual pathway's function in healthy...

Low-level near-infrared light-induced transcranial photobiomodulation (NIR-TPBM) is a promising technology for improving cerebral blood flow and metabolism. However, the effects of NIR-TPBM on the visual pathway's function remain poorly understood.

The aim was to assess the visual pathway's function changes in response to NIR-TPBM in young, healthy volunteers.

This single-center, randomized, controlled clinical trial included 98 healthy volunteers with a median age of 23.2 years. Participants were randomly assigned to two groups: NIR-TPBM (18 men and 30 women) and sham NIR-TPBM (19 men and 31 women). Eye-tracking procedures were conducted in both groups before and after either PBM or sham intervention. In the NIR-TPBM group, low-fluence NIR-TPBM was applied to the left and right fronto-temporal regions using a NIR-TPBM device (Elmedlife H^®, Nizhny Novgorod, Russian Federation). In the sham group, participants wore the NIR-TPBM helmet, but the NIR-TPBM mode remained deactivated. The duration of the sessions was identical for both groups. Changes in visual pathway function were evaluated by analyzing the dynamics of vertical and horizontal ocular vergence reactivity indices (VRx) using the EyeTracker application (BVG Software Group LLC, San Francisco, California, United States) on iPadOS 16 before and after the intervention. Statistical analysis was performed using nonparametric methods, with a significance level set at $p<0.05$ .

NIR-TPBM procedures led to a significant increase in both vertical and horizontal VRx values. Post-procedure vertical VRx was significantly higher than pre-procedure values (0.879 [0.761; 0.918] versus 0.774 [0.721; 0.929], $p<0.001$ ). Similarly, horizontal VRx increased significantly after NIR-TPBM compared with baseline (0.943 [0.848; 0.969] versus 0.772 [0.651; 0.890], $p<0.001$ ). No adverse effects were observed during or after the NIR-TPBM sessions.

NIR-TPBM enhances visual pathways function by increasing both vergence reactivity indices in young healthy volunteers.