Evidence from animal and human studies confirms outdoor time as a key strategy for delaying myopia onset, although the underlying mechanisms still require further research, according to a new paper published by the International Myopia Institute (IMI). Lead author Dr Elise Harb said the new paper “helps define the key questions and approaches that future research must address”.
The IMI’s open-access white paper, ‘IMI-the role of light in refractive development and myopia: Evidence from animal and human studies’, was published in Investigative Ophthalmology & Visual Science (IOVS).
This new IMI white paper examines the emerging science around how light may contribute to the protective effects of outdoor time. Animal studies show that different aspects of light, including intensity, colour, and day–night cycles, can shape eye growth, but translating these findings to humans is challenging. With growing interest in light-based therapies, the paper stresses that most remain experimental and highlights the critical need for well-designed clinical studies.
the paper reinforces the current evidence-based recommendation that children spend at least two hours outdoors each day
Key Insights from the White Paper
- Bright light exposure influences eye growth through retinal dopamine pathways, acting as a ‘brake’ on excessive axial elongation, a core driver of myopia development (animal-model evidence).
- Outdoor light intensity (>1000 lux) is associated with a less myopic refraction, although disentangling the role of light from outdoors is difficult (human evidence).
- Chromatic signals appear to play an important role in eye growth. Although species differences exist, studies in animal models show that narrow-band light significantly influences refractive development.
- Spectral composition of modern artificial lights (LEDs, screens) may play a role in increasing the risk of myopia, but their effects in humans remain unclear and require further research.
- Circadian rhythm disruption, sleep timing, and night-time light exposure may play a role in refractive development, though human evidence is currently inconclusive.
- Red-light and other chromatic light-based therapies are under investigation, but most remain experimental; long-term efficacy and/or safety are not yet established.
- Critical knowledge gaps remain regarding optimal light intensity, spectrum, and timing for myopia prevention, underscoring the need for well-designed clinical trials using modern wearable technologies.
- Standardising how we report light is critical, as different light sources have unique qualities that affect the eye differently. Where possible, studies should report the full spectrum of light (radiance), not just its intensity.
Clinical Recommendations
While specific light-based clinical recommendations cannot be made due to insufficient evidence, the paper reinforces the current evidence-based recommendation that children spend at least two hours outdoors each day. Importantly, wearing sunglasses or hats does not diminish the protective benefits of outdoor exposure. While specific light parameters require further clarification, clinicians can confidently promote outdoor activity as a validated, low-cost public health intervention to delay myopia onset.
Access the paper here.
