Blue Light Defocus Induces A Positive Effect on Refractive Status and Ocular Health: A Randomized Crossover Trial

This randomized crossover trial investigates the effects of blue light defocus display technology on refractive status, axial length (AL), retinal blood flow, and visual function in adults. Twenty-one participants completed all four interventions: 0D, 1D, 2D defocus, and 1D defocus with 30 % blue light filtering (1D+BLF) in a randomized order during standardized visual tasks. Pre- and post-task assessments include refraction, AL, choroidal thickness (ChT), retinal defocus, reading efficiency, and visual fatigue. Results demonstrate that 1D defocus reduces spherical equivalent refraction (SER) (-4.35 ± 2.66 D to -4.21 ± 2.66 D, P = 0.045) and increases ChT (P = 0.003), while 1D+BLF induces axial elongation (P = 0.026). Both 1D and 2D defocus are linked to increased ChT, whereas 0D and 1D+BLF groups exhibited hyperopic defocus trends. Reading speed and efficiency improve in the 1D group (p < 0.05), while visual fatigue and blink frequency increase significantly in the 0D group (p = 0.001). Linear regression identifies correlations between defocus and changes in choroidal volume, near convergence, and fusional reserves. These findings suggest blue light defocus technology may help mitigate hyperopic defocus, influence retinal perfusion, and alleviate visual fatigue, supporting its potential role in myopia prevention. Further validation in diverse populations and long-term studies is warranted.