- "You'll ruin your eyesight watching all that TV,"
my mother used to tell me when I was a child. It turns out that she may
have been right all along. The epidemics of shortsightedness in countries
such as Japan and Singapore are due solely to changes in children's lifestyle,
according to medical research. What's more, similar levels of myopia could
soon be seen in many Western countries. "As kids spend more time indoors,
on computers or watching TV, we are going to become just as myopic,"
says Ian Morgan of the Australian National University in Canberra.
- While shortsightedness is on the increase in most places,
it is no coincidence that it's rising fastest in the Far East, the researchers
believe. Take Singapore, where 80 per cent of teenagers are myopic, up
from 25 per cent just 30 years ago. Children there spend much time focusing
on close objects, such as study books and computers for playing the everincreasing
number of games available. To compensate, the eyeball is thought to grow
longer, so less effort is needed to see up close, but the elongated eye
can no longer focus on distant objects.
- Another study found myopia rates of 80 per cent in 14
to 18yearold boys studying in schools in Israel where the reading of religious
texts is emphasised. The rate for boys in state schools was 30 per cent.
- Karla Zadnik of the Ohio State University College of
Optometry in Columbus believes that parents may soon take action. "We
may start to get parents cutting the time their children spend on the computer
or watching television and encouraging them to spend more time outdoors."
This could achieve more than they realise. Studies show that children who
play sports are less susceptible to shortsightedness. Sport tends to involve
more focusing on far, rather than near, objects thus protecting the eye
from abnormal growth. Also, studies of animals have found that light protects
against myopia. Children who do become myopic are most likely to do so
between the ages of eight and 12, Zadnik says. "The condition usually
gets worse until about the age of 15 or 16, at which time the prescription
steadies out. Some get a bit more myopic progression in their twenties
or thirties, but it's nothing compared to what they experience at school
- Less telly time and more visits to the tennis club mightn't
be the only way to curb the onset of myopia. What children eat may also
be relevant. A team of evolutionary scientists, led by Professor Loren
Cordain of Colorado State University, found that a diet rich in sugar and
refined starches, including white bread and cereals, can cause shortsightedness.
They argue that these foods may affect the development of the eyes by stimulating
the production of the hormone insulin. High levels of insulin are matched
by a fall in levels of a similar chemical binding protein3 thought to
be involved in the growth of the eyeball and the lens.
- Evidence of the trend may be seen in Inuit people and
Pacific islanders: less than 1 per cent had myopia in the last century,
but rates have rocketed, in some cases to 50 per cent. This has been blamed
on the increase in reading after the rise of literacy and compulsory schooling.
But reading does not explain why the incidence of myopia has remained low
in communities that have adopted Western lifestyles but not diets, say
the scientists. "In Vanuatu, they have eight hours of compulsory schooling
a day, yet the rate of myopia in these children is only 2 per cent,"
says Cordain. The reason, she believes, is almost certainly that the Vanuatuans
eat fish, yam and coconut rather than white bread and cereals.
- There's more circumstantial evidence. Because being overweight
or having adultonset diabetes also involves having elevated insulin levels,
you would assume that such people would be more likely to develop myopia.
Studies have shown this to be the case. And changing diet cannot undo any
damage already caused, says Cordain, although it may prevent further degeneration.
- However, not everyone is persuaded by these theories.
Christopher Hammond of St Thomas' Hospital in London points out that shortsighted
children usually have shortsighted parents. And his latest study, launched
last week, has identified the first gene to be associated with myopia.
"Clearly, the increase in myopia in the Far East must be at least
partly due to environmental influences," he says. "However, only
the genetic argument can explain why the remaining 20 per cent of the people
in the Singapore study are not myopic, when they had a similar education.
Genes must be the protective factor."
- He points to one of the most famous US myopia studies.
"It showed that, while close reading was associated with myopia, by
far the most important contributing factor was family. The children whose
parents were not myopic had a 6 per cent prevalence of shortsightedness.
The children who had one parent with myopia had an 18 per cent prevalence,
and the children who had two myopic parents had a 33 per cent prevalence."
- Peter Warren of the Association of Optometrists in London
says: "I think we can only conclude that it is probably the case that
if you have a genetic disposition to myopia, then you are much more likely
to be susceptible to the environmental factors." He is keen to give
precautionary advice to shortsighted parents. "That advice includes
limiting the time spent by children on a computer. I also suggest that
children always use a good light when reading, and have a balanced diet.
Children should have plenty of time outdoors, but remember to protect their
eyes from too much exposure to the sun."
- Not surprisingly, pharmaceutical companies are trying
to develop cures. So far, there is nothing that prevents shortsightedness,
but there are products aiming to halt the progression in children. The
one most likely to be widely available in the UK and with least side effects
is Pirenzepine ophthalmic gel, which appears to slow the growth of the
axial length of the eye.
- Paul Lopez, the president of Valley Forge Pharmaceuticals
(the US company conducting a clinical investigation of the use of the gel
in children) says: "What we've seen in our trials to date is a 50
per cent reduction in the progression of myopia. It looks likely that the
product will be available in the UK from around 2008 or 2009." But
Hammond sounds a note of caution. "The gel is only shown to halve
the rate of progression, not stop it altogether. And there are questions
that can't yet be answered. For instance, are there any longterm side effects?
If children stop using the gel at any point, would their eyes then play
catchup to those who never took it, or would they remain less shortsighted?"
- He believes that behaviour during close work will be
the next area of investigation. "Does it help for children to take
breaks from reading or computer work by looking into the distance? This
is an area that's only just starting to be properly examined. The results
should be interesting."
- © 2004 Independent Digital (UK) Ltd http://news.independent.co.uk/uk/health_medical/story.jsp?story=556532