Indigo light prevents myopia in tree shrews

A tiny pair of spectacles helped researchers give one eye of a tree shrew a strong signal to become nearsighted while leaving the other eye for comparison. Under that controlled setup, exposure to indigo light completely prevented myopia from developing, according to a study led by Cincinnati Children's and the University of Alabama at Birmingham and published in Cell Reports Medicine on Aug. 18, 2026.

The wavelength mattered. Indigo light between 419 and 446 nanometers is plentiful in sunlight but poorly represented in standard white LED lighting. Earlier mouse studies had identified violet light near 380 nanometers, yet the lens of the human eye—and, the researchers found, the tree shrew's lens—blocks most wavelengths below about 400 nanometers. The team shifted slightly longer and found light that could still stimulate OPN5, a light-sensing receptor linked to eye development.

Myopia develops when the eye grows too long from front to back, leaving distant images out of focus on the retina. It usually begins in childhood and can progress through adolescence; severe myopia later raises the risk of retinal detachment, glaucoma and macular degeneration. The scale of the problem is one reason the lighting result matters: some experts predict that nearly 5 billion people (or 50% of the world's population) could be nearsighted by 2050.

And so, concretely? The immediate opportunity is not a new lamp on a store shelf, but a testable design change in places where children spend time indoors. Cincinnati Children's plans to install improved lighting in participating day care spaces and monitor children over time against facilities using standard lighting. The hospital has already been studying programmable, full-spectrum lighting in its neonatal intensive care unit, installed in 2021, but the myopia question still needs a child study.

The limit is clear. These results come from tree shrews, chosen because their eyes resemble human eyes, not from children. Richard Lang of Cincinnati Children's says the animal model is deliberately extreme, while Rafael Grytz of UAB was involved in the experiments. Whether adding indigo wavelengths to indoor light changes children's eye growth remains to be established in the planned trials.