Indigo light may prevent and treat myopia by restoring a missing wavelength in indoor lighting
核心洞察
A study published in Cell Reports Medicine found that indigo light (419–446 nm) completely prevented myopia (搜索) development in tree shrews, an animal model with human-like eyes.
The research suggests modern white LED lighting lacks indigo wavelengths, which may contribute to the global "myopia (搜索) boom" affecting children and adolescents.
Researchers developed a new metric, the μ-opic, to quantify how effectively different light wavelengths protect against myopia (搜索).
A new study published in Cell Reports Medicine suggests that controlled exposure to indigo light — wavelengths abundant in sunlight but largely absent from standard indoor white LED lighting — could serve as an effective treatment and prevention strategy for myopia (搜索), or nearsightedness. The research, led by scientists at Cincinnati Children's Hospital Medical Center and the University of Alabama at Birmingham (UAB), found that indigo light completely prevented the development of nearsightedness in tree shrews, an animal model whose eyes share important anatomical and optical similarities with human eyes.
"It is projected that nearly half of the world's population could be myopic by 2050," said Rafael Grytz, Ph.D., Dennis Endowed Professor of Glaucoma (搜索) Research in the UAB Department of Ophthalmology and Visual Sciences and lead author of the paper. "Myopia (搜索) results in higher risk to develop glaucoma, retinal detachments and other blinding disease later in life."
The right wavelengths for developing clear vision
Myopia (搜索) develops when the eye becomes too long from front to back, causing incoming light to focus in front of the retina rather than directly on it, which makes distant objects appear blurry. The condition often begins during childhood and may continue to worsen through adolescence. While standard glasses and contact lenses can correct blurry vision, they do not slow the development of the condition, and severe myopia raises the risk of serious eye problems later in life, including retinal detachment (搜索), glaucoma (搜索), and macular degeneration (搜索).
The indigo wavelengths were identified by optimizing activation of opsin 5 (搜索) (OPN5 (搜索)), a light-sensing receptor protein in the retina, while accounting for light filtered out by the ocular lens. Earlier work in animal models that rely on night vision suggested that violet light near 380 nanometers could suppress myopia (搜索) by activating OPN5. However, those wavelengths did not work in tree shrews, whose eye lenses — like human lenses — block most wavelengths below roughly 400 nanometers.
"Human lenses, and now we know tree shrew lenses, don't transmit a lot of light in the ultra-violet spectrum," said corresponding author Richard Lang, Ph.D., director of research in the Division of Ophthalmology at Cincinnati Children's. "They basically cut off most wavelengths below 400 nanometers. This finding pushed us to explore slightly longer wavelengths that could still stimulate OPN5 (搜索). Ultimately, we found that indigo light from 419 to 446 nanometers was the most effective at preventing myopia (搜索)."
Based on this finding, Grytz predicted the optimal wavelength that could stimulate OPN5 (搜索) in the animal model eye, leading the team to explore slightly longer wavelengths, including indigo wavelengths. The team ultimately established a new metric, called the μ-opic, that can quantify how effectively different light wavelengths may protect against myopia (搜索).
Why researchers study tree shrews
Tree shrews were chosen for the experiments because their eyes have anatomical and optical characteristics similar to human eyes. Grytz uses tiny spectacles designed for tree shrews that produce a strong signal encouraging myopia (搜索) in one eye, while the other eye provides a comparison.
"Even though tree shrews look like squirrels, they are a near-primate, with an eye very similar to that of humans, and so are a good model to study the cause of myopia (搜索) in the human population," Grytz said.
The researchers exposed the animals to several different wavelengths of light and tracked how their eyes changed. A biometer was used to measure eye shape and axial length, while an autorefractor monitored changes in refraction over time.
"The model of myopia (搜索) we use in the tree shrew is fairly extreme," Lang said. "So, if indigo light can suppress myopia in these tests, then it should also be quite effective in humans."
What indoor lighting may be missing
The findings add support to the idea that modern indoor environments may expose developing eyes to a different spectrum of light than humans experienced throughout most of their evolution. Standard white LEDs generally peak around 450 nanometers and provide plenty of longer-wavelength light needed for normal vision, but they contain relatively little indigo light, which appears to activate nonvisual opsins involved in biological processes beyond forming images.
"We evolved outside in the full-spectrum light provided by our sun," Lang said. "When we live inside, we don't get all the wavelengths the eye needs for normal refractive development, and so we get myopia (搜索). That's the basic message of this paper."
One possible strategy for reducing myopia (搜索) is for children to spend more time outdoors, where their eyes regularly switch focus between nearby and distant objects and their bodies receive the full spectrum of natural sunlight. However, researchers note that dramatically reversing society's shift toward indoor, technology-centered lifestyles may be difficult. A second possibility is to redesign indoor lighting so that it better reproduces the wavelengths present outdoors.
In 2021, building on earlier research into the effects of light on eye development, Cincinnati Children's became the first pediatric hospital to install a programmable, full-spectrum lighting system in its neonatal intensive care unit (NICU). Researchers are continuing to study the effects of that system.
The future of myopia treatment
Grytz founded Electric Indigo (搜索), a UAB startup that focuses on developing ways to practically manage myopia (搜索), with support from UAB's Bill L. Harbert Institute for Innovation and Entrepreneurship.
"At Electric Indigo (搜索), we have developed eyewear with LEDs in the frame that emit indigo light at controlled conditions to the eye to effectively treat and slow myopia (搜索) progression in children," Grytz said.
Grytz says this approach offers a simpler and new strategy that could surpass current treatment options, which may have difficult side effects and limited efficacy levels. Compared to the increasingly popular red-light therapy, Indigo Eyewear presents an easier approach to treatment by offering a practical method of exposure.
"If our hypothesis is confirmed that absence of indigo light indoors caused the myopia (搜索) boom, our eyewear will be the first treatment that attacks the root cause of this epidemic," Grytz said.
Next steps in clinical research
Although the tree shrew experiments produced strong results, researchers still need to determine whether indigo-enriched lighting can actually prevent myopia (搜索) in children. The next stage of the research is expected to involve installing improved lighting systems in participating daycare spaces. Children would then be followed over time so researchers could compare myopia rates with those seen in daycare centers using conventional lighting.
"What's our best option? It is to change the lighting environment inside," Lang said. "If future clinical studies confirm the findings, indigo-enriched lighting could become a safe, passive and scalable way to help reduce childhood myopia (搜索) risk."
The study was carried out as a collaboration between the research teams of Richard Lang at Cincinnati Children's and Rafael Grytz at UAB, with important contributions from Takahiro Yamashita at Kyoto University and Mehlika Inanici at The University of Washington. Funding came from several organizations, including the National Eye Institute of the National Institutes of Health, the National Institute of General Medical Science, the Japan Agency for Medical Research and Development, the EyeSight Foundation of Alabama, Research to Prevent Blindness, the Henry M. Hollis Fund, the Emma and Irving Goldman Scholar Endowed Chair, and the Cincinnati Children's Hospital Research Foundation.
Grytz and Lang declare they are inventors listed on pending patents for lighting devices related to this work. Grytz is the founder and CSO of Electric Indigo (搜索), a UAB startup in which UAB holds an ownership interest.