Associate Professor Scott Read
Short-sightedness, or myopia is one of the most common conditions effecting children’s vision today. It occurs due to the eye growing faster than normal, causing distant objects to appear blurred, and requiring glasses or contact lenses to provide clear vision. Although research examining the potential causes of short-sightedness dates back to the 1800s1, the complex, multifaceted nature of the condition, means the exact causes of the excessive eye growth underlying myopia is still not completely understood. Recent decades have also seen dramatic increases in the prevalence of myopia in young populations in many developed nations around the world, with myopia levels as high as 95% documented in some young populations in developed East Asian cities.2 Australian populations also appear to be at risk of this emerging ‘myopia boom’3 with a recent study predicting (based upon current trends) that the prevalence of myopia in Australia will approximately double by 2050.4 As well as leading to increased costs associated with glasses and contact lenses, rapidly rising levels of myopia also lead to significant public health impacts since the presence of myopia has been linked to substantially increased risks of developing a number of sight threatening eye conditions later in life.5
Spurred on by studies suggesting that children who spend greater time outdoors appear to be at lower risk of being short-sighted,6 our research has aimed to provide new insights into the factors involved in the development and progression of short-sightedness by examining the influence of light exposure upon childhood eye growth. To tackle this issue, we used small, wristwatch light sensors (capable of collecting thousands of light measurements per day) that were worn by each of the 101 children enrolled in the study. These detailed measures provided us with a comprehensive picture of each child’s pattern of typical daily light exposure, and when coupled with highly precise measures of eye growth (collected over 18 months), delivered the first direct evidence of a relationship between daily light exposure and eye growth in childhood.7 These results showed us that children typically exposed to less bright light throughout the day showed faster eye growth, and were at greater risk of the development and progression of short-sightedness. Greater bright light each day was associated with slower eye growth and therefore lower myopia risk. Although a range of different factors are known to impact upon eye growth and childhood myopia risk, our research identified an additional modifiable risk factor: that of daily light exposure.
Our findings suggests that spending less than 60 minutes a day in bright light appears to be a risk factor for faster eye growth (and hence development and progression of short-sightedness),8 and that increasing daily bright light by an extra 60 minutes a day is likely to have an impact upon eye growth. Since outdoor light is up to 100 times brighter than what we typically experience indoors, the easiest way of increasing children’s daily light exposure, is by taking the simple step of spending more daily time outdoors. In fact, a recent study of Chinese children confirmed that increasing outdoor time by 40 minutes a day significantly reduced the risks of myopia development.9 Given the already established health benefits of outdoor play in childhood, and our research now suggesting that spending more time in outdoor light is likely to have the added benefit of reducing children’s risk for myopia development and progression, can we really afford not to be encouraging our kids to be spending more time in the great outdoors?
- Cohn H. Handbook of the hygiene of the eye. Vienna and Leipzig: Urban & Schwarzenegger, 1892. https://archive.org/details/hygieneofeyeinsc00cohnrich
- Jung S-K, Lee JH, kakizaki H, Jee D. Prevalence of myopia and its association with body stature and education level in 19-year-old male conscripts in Seoul, South Korea. Invest Ophthalmol Vis Sci. 2012; 53: 5579-5583. http://iovs.arvojournals.org/article.aspx?articleid=2166142
- Dolgin E. The myopia boom. Nature. 2015;519: 276–278. http://www.nature.com/news/the-myopia-boom-1.17120
- Holden BA, Fricke TR, Wilson DA, Jong M, Naidoo KS, Sankaridurg P, Wong TY, Naduvilath TJ, Resnikoff S. Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050. Ophthalmology. 2016;123:1036-1042. http://www.sciencedirect.com/science/article/pii/S0161642016000257
- Holden B, Sankaridurg P, Smith E, Aller T, Jong M, He M. Myopia, an underrated global challenge to vision: where the current data takes us on myopia control. Eye. 2014; 28: 142-146. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3930268/
- Rose KA, Morgan IG, Ip J et al. Outdoor activity reduces the prevalence of myopia in children. Ophthalmology. 2008; 115; 1279-1285. http://www.sciencedirect.com/science/article/pii/S0161642007013644
- Read SA, Collins MJ, Vincent SJ. Light exposure and eye growth in childhood. Invest Ophthalmol Vis Sci. 2015;56:3103-3112. http://iovs.arvojournals.org/article.aspx?articleid=2466239
- Read SA. Ocular and environmental factors associated with eye growth in childhood. Optom Vis Sci. 2016; 93: 1031-1041. http://journals.lww.com/optvissci/Citation/2016/09000/Ocular_and_Environmental_Factors_Associated_with.5.aspx
- He M, Xiang F, Zeng Y, Mai J, Chen Q, Zhang J, Smith W, Rose K, Morgan IG. Effect of Time Spent Outdoors at School on the Development of Myopia Among Children in China: A Randomized Clinical Trial. JAMA. 2015; 15: 1142-1148. http://jamanetwork.com/journals/jama/fullarticle/2441261