Photobiomodulation Increases Eye Movement Conjugation in Healthy Volunteers

The aim of the study was to evaluate changes in eye movement conjugation in healthy volunteers in response to transcranial photobiomodulation (tPBM).

54 healthy volunteers (23 men, 31 women; median age was 23.5 years) were included in this retrospective, non-randomized study. Eye tracking (ET) was performed using the iPad app EyeTracker with a sampling rate of 20 Hz before and after 10 min tPBM (810 nm). The tracker calculated angular velocities in the vertical and horizontal planes (AV; vertical and horizontal). Data are shown as a median [interquartile range]. Pearson's correlation coefficients were used to assess agreement between computed variables. This coefficient value was designated as the vergence reactivity index (VRx), which reflects the eye movement conjugation. The differences were determined using the Wilcoxon T-criterion. The level of significance was p < 0.05.

Vertical and horizontal VRx after tPBM were significantly higher than before the procedure: 0.878 [0.843; 0.902] vs. 0.783 [0.702; 0.829], p < 0.001, respectively and 0.875 [0.834; 0.912] vs. 0.927 [0.921; 0.93], p < 0.001, respectively.

Transcranial PBM causes a significant increase in vertical and horizontal vergence indices, which indicates an improvement in eye movement conjugation in healthy volunteers.