Myopia: Why Are More and More Children Getting Short-sighted?

Kids are being diagnosed with myopia at a much younger age than before, and more and more kids are needing eyeglasses.

In Singapore, over 80% of 18 year-olds are myopic. And this ranks the country as having one of the highest rates of myopia in the world. Also, 28% of 7-year-old Singaporeans are myopic compared to about 1% in Australia. This is also 1.5-3 times higher than similarly aged white or black populations in the United States.

(This website gives estimates of the prevalence rates of myopia across different countries. http://www.wrongdiagnosis.com/m/myopia/stats-country.htm)

Why is that so?

It is believed that genes, the environment, and gene-environment interactions together cause myopia.

Genetically, Asians seem to be predisposed towards it. Besides Singapore, China is also reporting very high rates of myopia. In both Singapore and Xiamen schoolchildren, those with at least one myopic parent were three times more likely to have early-onset myopia. In another local study, myopia clustered significantly in families. Amongst those who live in urban areas, Asians had higher prevalence than non-Asians. In general, estimates of myopia rates in the Western countries are lower than those in Asian countries.

However, there are also environmental reasons. Singaporeans and Malaysians have similar genetic makeup but Singaporean Malays, Indians and Chinese all had higher prevalence rate than Malaysian Malays, Indians and Chinese (SM Saw, 2006¹).

Myopic rates in the rural areas are lower than those in the urban areas. They are also lower in the less developed countries as compared to the developed countries². For example, only 5.8% of schoolchildren in Mongolia had myopia, low in comparison to reported studies for other Far Eastern countries³.Children in rural areas tend to read less, have more outdoor activities, watch less TV and do not use the computer.

This would suggest that causes would include long periods of intense near-work like reading, watching the television, or computer usage. Parents also blame too much homework and studying as causes. And they are not wrong, because researchers have found that myopia progressed more rapidly during the school term than during the summer vacation⁴. It was also found that 15-year-olds in Nepal who were not in school had a prevalence rate of only 2 percent and the same was true in rural India.

Children who had 3 or more hours per week of near-work classes outside school had a higher rate of myopia. This suggests that there may be an association between near-work and myopia, even at a young age.

Advice for parents?
Encourage children to engage in more outdoor activities.

Reduce the duration of continuous near-work.

Remind children to have good reading habits:
When reading, hold books at least 30cm away from the eyes.
Sit upright in a comfortable chair.
Ensure adequate lighting: avoid excessive glare shining directly onto book or face.

Remind children to have proper computer usage:
Place monitor screen about 50cm away from eyes.
Ensure adequate lighting.
Adjust monitor screen to reduce glare or reflection.

Remind children to have good TV-watching habits:
Sit at least 2 meters away from the screen.
Room light should be switched on.
Center of screen should be at eye level or lower.
Do not lie down while watching TV programs.

This last one is regarding breastfeeding and early nutrition. Early visual experiences affect the growth of the eye, and nutritionally mediated deficiencies in retinal or visual development in infancy may predispose to myopia. In a breastfed infant,breast milk is the main source of many micronutrients including docosahexaenoic acid, which is important for photoreceptor and cortical neuronal development.

There is an association between breastfeeding and myopia, not a causality relationship, but it is worth considering, if possible. Chong et al in the Journal of the American Medical Association (2005) reported that children who were breastfed had lower myopia prevalence (62%) than children who were not breastfed (69.1%). A history of being breastfed was associated with decreased odds of myopia. Duration of breastfeeding was not associated with myopia and the type of breastfeeding (exclusive,mostly, or partly) was not significantly associated with myopia.

Some ongoing research studies on myopia

A large-scale study on 3,000 infants and pre-schoolers, aged 6 months to 6 years, was launched earlier this year in Singapore. It will involve the hospitals, clinics and more than 10 doctors and scientists, including Associate Professor Saw Seang Mei from the National University of Singapore (NUS).

A similar is an ongoing one done in America on 12,000 children. These studies may have interesting findings. For example, the risk factors causing myopia in young children may be known. Also, the answer to the tendency of Asians to get myopia more than Caucasians.

A multi-agency research project involving SERI, NUS, the Defence Medical Environment Research Institute (DMERI), Genome Institute of Singapore (GIS) and Duke University, in the United States, to investigate gene-environment interactions that cause myopia.

Neural Vision Correction programme, a pilot trial to re-programme children's brains to see better is held at the Singapore Eye Research Institute.

Sources
1. SM Saw. British Journal of Ophthalmology 2006;90:1230-1235
2. Ophthalmic Physiol Opt. 1994 Oct;14(4):378-82
3. Optometry & Vision Science. 83(1):53-56, January 2006
4. Fulk GW, Cyert LA. J Am Optom Assoc. 1996 Dec;67(12):749-54