Exposure to indigo light prevented myopia in a tree shrew model with human-like visual characteristics, according to research led by Cincinnati Children’s and the University of Alabama at Birmingham (UAB).

The study, published online August 18 in Cell Reports Medicine, focused on short-wavelength indigo light, which is abundant in sunlight but is poorly represented in standard white LED lighting. Researchers reported that indigo exposure completely prevented experimentally induced myopia in tree shrews.

They used tree shrews because shrew eyes share anatomical and optical characteristics with human eyes. The animals were fitted with spectacles that produced a strong myopia-inducing signal in one eye, while the other served as a comparison. Axial length was measured using a biometer and refractive changes were tracked with an autorefractor.

Previous mouse research has shown that violet light near 380 nm could suppress myopia through the light-sensing receptor opsin 5, or OPN5. However, that wavelength was ineffective in tree shrews because their lenses, like human lenses, block most light below approximately 400 nm. Researchers subsequently found that indigo wavelengths from 419 to 446 nm were most effective at preventing myopia.

Standard white LEDs typically peak around 450 nm but provide little of the indigo light that appears to stimulate nonvisual opsins, according to the study. "The model of myopia we use in the tree shrew is fairly extreme," said Richard Lang, PhD, director of research in the Division of Ophthalmology at Cincinnati Children's in a press release about the study. "So, if indigo light can suppress myopia in these tests, then it should also be quite effective in humans."

The researchers cautioned that the findings still require human testing. In the planned next phase, the researchers will install indigo-enriched lighting in participating daycare settings and monitor children over time to compare myopia development with children in facilities that use standard lighting. OM