Nearsightedness is on the rise, and the amount of time spent indoors is a factor. A new study suggests that a missing ingredient in indoor lighting, specifically indigo light, could be a potential cause of this vision problem.
Children are spending more time indoors than ever before, and at the same time, rates of nearsightedness are climbing around the world. The study found that exposure to a particular range of indigo light, ranging from 419 to 446 nanometers, completely prevented myopia from developing in tree shrews.
Understanding Myopia
Myopia occurs when the eye grows too long from front to back, causing incoming light to focus in front of, rather than directly on, the retina. This results in distant objects becoming blurry. While glasses and contact lenses can correct vision, severe myopia can increase the risk of retinal detachment, glaucoma, and macular degeneration later in life.
The problem is growing, with some experts predicting that nearly five billion people, half the world’s population, could be nearsighted by 2050. Children who spend more time indoors and less time outdoors appear to be particularly vulnerable.
The Study
The study was conducted by a team from the Cincinnati Children’s Hospital Medical Center and the University of Alabama at Birmingham. They fitted tree shrews with tiny spectacles designed to create a powerful myopia-inducing signal in one eye, while the other eye served as a comparison.
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The team then exposed the animals to different wavelengths of light and carefully monitored changes in their eyes over time. They used a biometer to measure the axial length of the eye and an auto refractor to measure changes in refraction.
The researchers were particularly interested in a light-sensitive receptor called Opson-5 or OPN5. Earlier experiments in mice had suggested that violet light near 380 nanometers could suppress myopia. However, human lenses, like those of tree shrews, block most ultraviolet light below about 400 nanometers.
Findings and Implications
The study found that indigo light ranging from 419 to 446 nanometers was most effective in preventing myopia. This finding has implications for the design of indoor lighting, which could potentially be redesigned to help protect children’s developing vision.
Standard white LED lighting contains relatively little of this portion of the spectrum, while sunlight is rich in it. Richard Lang said, “We evolved outside in the full-spectrum light provided by our sun. When we live inside, we don’t get all the wavelengths the eye needs for normal refractive development, and so we get myopia.”
They hope to install specially designed lighting in daycare centers and follow children over time, comparing rates of myopia with those in facilities using conventional lighting. For now, the results offer a possible explanation for why the outdoors appears to protect children’s vision.
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No one yet knows for certain whether changing indoor lighting will reduce myopia in children. If it does, something as ordinary as the light above a child’s desk could eventually become part of protecting their eyesight. The study is published in Cell Reports Medicine.
The amount of time spent indoors is a factor in nearsightedness.
The researchers’ interest in the light-sensitive receptor Opson-5 or OPN5 was sparked by earlier experiments in mice, which suggested that violet light near 380 nanometers could suppress myopia. However, the fact that human lenses block most ultraviolet light below about 400 nanometers led the team to investigate slightly longer wavelengths, ultimately discovering the effectiveness of indigo light ranging from 419 to 446 nanometers.
The study’s use of tree shrews as a model for human myopia was significant, as these animals have eyes that share anatomical and optical features with human eyes. The team’s plan to install specially designed lighting in daycare centers and follow children over time will provide valuable insights into the potential benefits of indigo-enriched lighting for preventing myopia in children.
Standard white LED lighting contains relatively little of the indigo spectrum, while sunlight is rich in it. As researcher Richard Lang noted, “We evolved outside in the full-spectrum light provided by our sun. When we live inside, we don’t get all the wavelengths the eye needs for normal refractive development, and so we get myopia.”
