Evidence from animal and human studies confirms light from outdoor time as a key strategy for delaying myopia onset, although the underlying mechanisms still require further research.
December 9, 2025
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SYDNEY — The International Myopia Institute (IMI) has released a new open-access white paper, IMI—The Role of Light in Refractive Development and Myopia: Evidence from Animal and Human Studies, published in Investigative Ophthalmology & Visual Science (IOVS). The paper provides a comprehensive review of how light exposure influences eye growth, synthesizing decades of research from both animal models and human epidemiological studies
Outdoor time remains one of the most consistent protective factors against myopia onset in children, but the mechanisms behind this effect are not yet fully understood.
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—including intensity, color and day to night cycles—can shape eye growth. However, 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.
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 illumination significantly influence 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.
- Standardizing how we report light is critical, as different sources have unique qualities that affect the eye differently. Where possible, studies should report the full spectrum (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
Quotes from Lead Authors
Dr. Elise Harb, OD, PhD, FAAO:
“The association between outdoor time and delayed myopia onset is well established, but the mechanisms remain unresolved. Our review helps define the key questions and approaches that future research must address.”
Dr. Regan Ashby, PhD:
“Animal studies have revealed how strongly light can influence eye growth but translating these findings to humans is complex. By bridging animal and human evidence, this white paper highlights both what we know and what we urgently need to uncover to inform future prevention strategies.”
Access the White Paper
The full white paper and concise clinical summary is freely accessible here: https://myopiainstitute.org/imi-white-papers-clinical-summaries/
