You may not realize that sunlight is critical for good vision in children, but in my opinion, the science provides incontrovertible evidence. A new study has corroborated the findings of a number of earlier investigations.
The Daily Mail, a UK newspaper, reported that “Too much time indoors damages children’s eyes: Lack of natural sunlight thought to be driving up rates of short-sightedness among the young.[i]” They also mention that Chinese children are now being sent to schools with translucent walls to prevent the nearsightedness associated with lack of sunlight.
Other interesting statements in the article are the following:
- Nearsightedness is rising, now affecting around 40% of the population.
- Yet, in hunter-gatherer societies that live mainly outdoors, the incidence of nearsightedness is only 0.5% of the population.
- Spending an extra 40 minutes per day in the sun has been shown to improve children’s sight dramatically.
It doesn’t take a rocket scientist to determine that myopia is caused by lack of sunlight exposure. The evidence has been building for years. For example, researchers showed that the lowest risk of myopia among 12-year-old students was found among those who reported the highest levels of outdoor activity.[ii] Some might surmise that the key ingredient was exercise, but that idea was refuted by the fact that there was no association between indoor activity and myopia. Something besides exercise had to be leading to the lower risk of myopia among children who were actively outdoors; it had to be sunlight. The lower risk of myopia persisted after adjusting for genetic factors, ethnicity and the amount of near work. This is important, because for many years there was an assumption that long hours of study indoors, staring closely at books (near work) and never focusing on distant objects, led to myopia. This study belied that error.
This same research showed that the prevalence of myopia among Chinese children living in Singapore was 29.1%, whereas Chinese children living in Sydney, Australia, had a prevalence rate of only 3.3%. The children in Sydney spent about 13.8 hours per week outdoors compared to 3.05 hours in Singapore. In other words, the children who spent most or their lives indoors had 9.5 times the risk of developing myopia!
Optimal refraction of light is the key to good vision. Refraction is the change of direction of a ray of light as it passes from one medium into another. In the case of vision, it is necessary for the eye to refract light that centers it in a manner that forms a clear image on the retina. With myopia, the eyeball becomes elongated and cannot properly focus the light from distant objects, which make those objects appear fuzzy. One of the mechanisms by which lack of sunlight leads to myopia may be an improper development the eyeball that interferes with proper refraction of light. It has been shown that in young adults with myopia, refractive error is inversely associated with ocular sun exposure,[iii] indicating incorrect eye development. Obviously, the eyes need sunlight to develop perfect vision, but this does not indicate that we should ever stare at the sun; we simply need to be outdoors during sunny hours.
Myopia in children also leads to a higher risk of both Glaucoma and cataracts in adulthood.[iv] This means that the advice to avoid sunlight to avoid these vision diseases is misguided. In general, the promotion of sun avoidance might be considered criminal, as it causes not only to vision problems, but a host of other diseases that lead to a deterioration of the human condition.
Let’s all return to regular, sensible and safe sun exposure; the human being did not evolve in a sunless box!
[ii] Rose KA, Morgan IG, Ip J, Kifley A, Huynh S, Smith W, Mitchell P. Outdoor activity reduces the prevalence of myopia in children. Ophthalmology 2008 Aug;115(8):1279-85.
[iii] McKnight CM, Sherwin JC, Yazar S, Forward H, Tan AX, Hewitt AW, Pennell CE, McAllister IL, Young TL, Coroneo MT, Mackey DA. Myopia in young adults is inversely related to an objective marker of ocular sun exposure: the Western Australian Raine cohort study. Am J Ophthalmol. 2014 Nov;158(5):1079-85