Nearsightedness: How can going for a walk help?

Myopia, or nearsightedness, a condition that causes distant objects to appear blurry, is becoming more prevalent worldwide. Spending more time engaged in near-work activities, such as reading, is known to worsen the condition, while spending time outdoors can help slow its progression. However, the reasons for these effects are not yet fully understood.

Retinal images are processed in the brain with the help of ON and OFF visual pathways. These pathways respond differently to luminance contrast and visual motion and their stimulation plays an important role in myopia development.

A team of researchers from SUNY College of Optometry in New York, NY, conducted an eye tracking study to investigate the impact of reading and walking on ON and OFF visual pathways. They recruited subjects with different optical conditions and used Tobii Pro Glasses to track eye movements during two visual tasks: reading a document on a computer screen, and walking. They hypothesized that myopia progression is driven by a poor stimulation of ON visual pathways, which disrupts the ON/OFF response balance.

The results show that reading reduces stimulation of the ON pathways. In contrast, walking stimulates both ON and OFF pathways evenly. Outdoor activities provide the retina with bright light, which strongly increases the visual responses from ON pathways. In addition, outdoor activities stimulate ON pathways involved in reflexes of image-retinal stabilization triggered by visual motion. Consequently, spending time outdoors and engaging in visual navigation tasks may be the best approach to suppressing myopia progression.

The study also examined the difference between reading white text on a black background versus black text on a white background and concluded that reading white text on a black background, due to increased contrast, provides a more balanced stimulation of ON and OFF visual pathways. However, this type of reading still lacks visual motion, deeming it likely insufficient to improve myopia. To prevent myopia progression, the authors propose a visual diet that includes bright light, high contrast, frequent luminance transients, and visual motion to drive reflexes of image-retinal stabilization.

Publication

Poudel, S., Rahimi-Nasrabadi, H., Jin, J., Najafian, S., & Alonso, J. M. (2023). Differences in visual stimulation between reading and walking and implications for myopia development. Journal of Vision, 23(4), 3-3. April 2023.