Effects of chromatic light interventions and wavelengths on ocular biometry in human myopia: A systematic review and meta-analysis

Abstract

Studies highlight the use of different wavelengths of light as emerging interventions to slow myopia progression in children. This review evaluates the effects of different wavelengths of chromatic light interventions on ocular biometry in humans. A literature search of MEDLINE, CINAHL, Scopus, ProQuest Central, Web of Science, and trial registries identified thirty-seven studies examining the effects of either long-term (4 weeks- 24 months) or short-term (between 10–120 min and ≤ 4 weeks) monochromatic light exposure. A random-effects model was used to calculate the weighted mean difference (WMD) and 95 % confidence intervals (CI) in spherical equivalent refraction (SER), axial length (AL) and subfoveal choroidal thickness (ChT). In studies examining long-term exposure to both long- and short-wavelength light, significant changes in AL, SER, and ChT were observed primarily with long-wavelength red light used in repeated low-level red light (RLRL) therapy. RLRL resulted in a significant reduction in AL and SER, and an increase in subfoveal ChT compared to a control group wearing single vision spectacles (SVS) at both 6 and 12 months (WMD at 6 and 12 months, AL:0.24 and –0.36 mm; SER: 0.31 and 0.77 D; ChT: +32.12 and +31.78 µm). Exposure to short-wavelength (blue and/or violet light) resulted in only a modest change in AL and myopia progression in children [mean change (95 % CI) at 12 months, AL:0.04 mm (–0.15 to 0.07); SER: 0.04 D (–0.16 to 0.24)]. Short-term exposure to both long- and short-wavelengths on ocular biometry in young adults showed equivocal results. LED-based blue light (454–456 nm) induced choroidal thickening and a reduction in AL, whereas red light produced the opposite effects. In conclusion, longer-term exposure to RLRL and violet light can slow myopia progression in children, with RLRL showing a stronger effect. Short-term exposure to different wavelengths offers insights for developing newer light-based myopia therapies.