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Health, Beauty & Fashion

Helping young eyes

Urban and genetic factors contribute to myopia in children
Asia One - June 21, 2011
By: Tan Shiow Chin
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Helping young eyes

IT is not unusual to see young children wearing spectacles nowadays.

This is not just a coincidence, as it was reported at the 2008 International Myopia Conference in Cairns, Australia, that over 50% of 11- to 13-year-olds living in urban populations across East Asia have myopia, or shortsightedness.

In highly urbanised countries like Singapore and Taiwan, the number of 18-year-olds who are myopic can reach up to 80 to 85%.

And it is not just the fact that more young ones are needing spectacles nowadays; their "power", or refractive error, is also increasing more rapidly after onset than before. This means that they have to change their spectacle lenses more frequently, in order to be able to see properly.

According to Brien Holden Vision Institute Myopia Programme Director, Associate Professor Dr Padmaja Sankaridurg, research showed that between 1990 and 2000, there was a 10% increase in the number of young myopia cases. "There seemed to be a big jump in the number of children getting myopia, and this raised a red flag for us."

She adds: "Not only did the prevalence increase, but also the rate at which the myopia was progressing."

More and more children, she says, were requiring lenses of -6 Diopter (D) or more, which is classified as high myopia. This level of myopia is significant because at -6D, the expansion of the eyeball causes it to weaken, and the possibility of a retinal break, which can lead to blindness, becomes higher.

Urban factor

With myopia, a person is unable to see distant objects clearly. The reason for this is anatomical - the eyeballs are larger than they need to be. Because of this, the eye is unable to focus images that are far directly onto the retina.

The retina is found at the back of the eye; its main function is to receive the images we see, which are then sent to the brain for processing via the optic nerves that connect the eye to the brain.

For people who are short-sighted, images that are far fall in front of the retina, instead of on it, resulting in blurry vision. (See graphic) Near images are still clear as the lens of the eye can still compensate in terms of focusing those images directly onto the retina.

Both genetic and environmental factors are believed to play a role in the development of myopia.

Children whose parents are both shortsighted, have a one-in-three chance of becoming shortsighted themselves; while those with only one myopic parent have a one-in-five chance of developing myopia.

Meanwhile, environmental factors are postulated to play a big role in the large increase in myopia cases among urban populations. Says Assoc Prof Sankaridurg: "Take any country in the world, there seems to be something about the urban environment that contributes to myopia.

"Researchers (in this area) talk about near work and closed environments; is myopia increasing because the eye is adapting to near work?"

Examples of near work include using the computer, reading and writing.

As such, it is not surprising that researchers have speculated that East Asian pride in academic achievements might have contributed to this phenomena. However, as Assoc Prof Sankaridurg says: "How can we tell parents to ask their child not to study?"

She shares that a study she conducted in China, involving school children, showed that the progression of myopia during the summer was half that of the progression during winter.

With the conducive weather and school holidays occurring during summer, the children were involved in more outdoor activities, as compared to winter, when they would be in school and indoors a lot. "The risk of having myopia seems to be reduced when you have outdoor activities," she says.

Supporting the theory is the difference in myopia cases between rural and urban populations. "In countries like China and India, the myopia prevalence rate in rural areas is around 40%, while in the urban population, it is close to 55-75%," she says.

A global solution

Parents can encourage their children to spend more leisure time outdoors, instead of just playing computer games or watching television, as well as taking regular breaks to rest their eyes when they use the computer, do homework or study, to help prevent or slow down myopia,

In addition, Assoc Prof Sankaridurg and her colleagues, under the auspices of Vision CRC, have also come up with a new type of lens to help decrease the progression of myopia.

Vision CRC is one of the Australian Government's Cooperative Research Centres, specialising in eyecare. The Brien Holden Vision Institute is one of the participants in its various programmes, including its Anti-Myopia Programme.

"We started looking at what it actually means when the eye is progressing, as not all eyes progress at the same rate," says Assoc Prof Sankaridurg.

What they found was that while wearing spectacles helped in correcting central vision, peripheral images were actually being focused behind the retina due to the spherical shape of the eyeball. As such, the researchers hypothesised that the progression of myopia was due to the eye "chasing the image" by growing larger in order to "catch" the image that is being projected behind the eye.

This is particularly pronounced in children and young teens, as they are already in the stage of rapid growth and development; thus, accounting for their rapid progression of myopia.

"What we are trying to do now is design lenses that provide global correction, so that all images fall on the back of the eyeball," Assoc Prof Sankaridurg shares.

The team has already carried out a random clinical trial at a centre in Guangzhou, China, involving 210 children aged six to 12 years over a year.

The results showed that the new lenses that provide global correction slowed down the progression of myopia in the children who wore them by about 30%, as compared to those who wore regular single-vision lenses.

These new lenses are being produced by Vision CRC's industry partner, Carl Zeiss Vision, under the trade name Myovision.

While Carl Zeiss Vision Malaysia sales manager Paul Ho acknowledges that Myovision lenses are more expensive than regular single-vision lenses, he adds that in the long run, parents will save money as their child would not need to change their spectacles as often as compared to if they use regular lenses.

According to Ho, regular single-vision lenses on the market now cost about RM150 (S$61) to RM180 (S$73), while Myovision lenses cost about RM360 (S$146).

 

 

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