Short-sightedness (the medical term for which is ‘myopia’) is a common condition in industrialised countries. This condition probably has many potential underlying causes. Some of these were reviewed in a recent paper published in the journal Optometry and Vision Science . One quite clear finding from this review was that spending time outdoors is linked with a reduced risk of myopia in children.
One potential explanation here is that kids who spend more time indoors are also likely to spend more time engaging in activities that in common culture are often associated with short-sightedness such as book reading and computer work. In reality, though, the review found no good relationship between so-called ‘near work’ and myopia.
The authors of this review speculate that being outside might help protect against myopia because it encourages children to focus on distant objects. They also suggest it might have something to do with sunlight. Anyway, whatever the explanation, I think this research points to yet another reason why children should be encouraged to spend a good chunk of their time outdoors (and not too much of their time cooped up at home).
This review reminded me of some previous work that has looked into the potential role that diet has in the development of myopia. Some scientists have speculated that a glut of carbohydrate in the diet sets up biochemical imbalance that can lead to enlargement of the eyeball during childhood (something that would predispose to short-sightedness). Below, I have pasted in a previous piece where I discuss this mechanism. There are, I think, many good reasons for not feeding kids a diet rich blood-sugar disruptive foods. Improved vision appears to be one of them.
1. McBrien NA, et al. Myopia: Recent Advances in Molecular Studies; Prevalence, Progression and Risk Factors; Emmetropization; Therapies; Optical Links; Peripheral Refraction; Sclera and Ocular Growth; Signalling Cascades; and Animal Models. Optom Vis Sci. 2009;86(1):45-66.
Could carbs cause short sightedness? – 22 September 2003
Amongst those who know me well I have a reputation as a bit of a philistine. In my 37 years on this planet, I have read just two novels (neither one of them a great work of literature) and even managed to fail my English literature ‘O’ level. The truth is, I’ve always struggled taking in the written word, and view the expression ‘reading for pleasure’ as a contradiction in terms. Even from a young age, I studiously avoided reading matter, and therefore felt rather hard-done-by to find myself in need of glasses for short-sightedness at the age of 13. My personal experience certainly seemed to be one in the eye for the commonly-held notion that short-sightedness is the result of bookishness and scholarly endeavour.
Recently, I decided to cast my eye over the research into the causes of short-sightedness (myopia). Several studies show that populations with no system of formal education have very low rates of myopia. Individuals leading primal, rural existences have been found to have rates of myopia of around 0 ” 2 percent, compared to the 30-odd per cent seen in the West. Also, research shows that when populations migrate from a traditional way of life, to a more urbanised existence, rates of myopia shoot up within a single generation. However, while the available evidence seems to support the notion that reading plays a big part in the development of myopia, the association is not as clear as it seems at first sight.
Research shows that exposure to books and formalised education may have only a marginal effect on eyesight. In more than one study, rates of myopia have found to be surprisingly low in populations that have formalised education programmes. One piece of research, for instance, that in a population living in a rural, non-Westernised manner, rates of myopia were only about 1 per cent despite eight hours of schooling each day. Also, there is evidence that living in an urbanised environment is associated with a high risk myopia even in individuals who have had no formal education. The evidence suggests that blaming our susceptibility to myopia on reading is a bit, well, short-sighted.
An obvious place to look for alternative explanations for what causes myopia is the diet. In particular, some scientists have turned their eyes to the potential role that the carbohydrate-rich Western-diet may play in short-sightedness. While we are often encouraged to consume starches such as bread, potatoes, rice and pasta, one effect these foods have in the body is to stimulate the production of the hormone insulin, along a related compound called insulin-like growth factor 1 (IGF-1). Too much IGF-1 has the capacity to stimulate excess growth of the eyeball during development – itself the fundamental defect in short-sightedness.
The detrimental effect of sugar and starch on eyesight is corroborated by evidence that myopic individuals are more likely to suffer from other conditions associated with the consumption of carbs such as diabetes and dental decay. This link between the Western diet and short-sightedness is just part of an accumulating stack of evidence showing that carbohydrates are not the panacea the dietetic establishment and food industry would have us believe them to be. It seems that the dietetics slavish adherence to the notion that grain-based carbohydrates should take prominence in the diet is an act of blind faith.
Cordain L, et al. An evolutionary analysis of the aetiology and pathogenesis of juvenile-onset myopia. Acta Ophthalmol Scand. 2002;80(2):125-35.