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Fact: Myopia is worsening in Singapore
Myopia is a rapidly worsening public health problem in Singapore.
Surveys have indicated that myopia afflicts 25% of 7 year olds,
33% of 9 year olds, 50% of 12 year olds and more than 80% of 18
year old males in Singapore.
Theory: Cause of
myopia
We still do not have a complete explanation
for the development of myopia. There is certainly a genetic factor
which makes certain people (and ethnic groups) more susceptible
to the development of myopia. However, this does not explain the
rapid increase in the prevalence of myopia in Singapore over the
last 3 generations. The gene pool has not changed, but the prevalence
of myopia has accelerated rapidly. This strongly suggests that environmental
influences interacting with the genes have played a major role.
A recent study in America suggested that leaving
the lights on at night when babies were asleep might have predisposed
them to developing myopia. We have also been able to induce myopia
in chicks, tree shrews and monkeys simply by manipulating their
visual environment. This is further evidence of the major role played
by the environment.
Whilst we cannot yet pinpoint the exact environmental
factor, it is quite likely that this is related to the heavy amount
of reading and near work our children are exposed to, which is certainly
much higher than that in the past.
Fact: True myopia
is irreversible
Myopia arises when the eyeball grows too long. Once this growth
has occurred, it is not reversible. However, there is also another
type of spurious myopia that is due to excessive spasm of the internal
focussing muscles within the eye. This type of spurious myopia can
be reversed by relaxation techniques, and practitioners of this
art sometimes wrongly claim that they have "cured" myopia.
Although true myopia is irreversible, we can
compensate for it by wearing spectacles, contact lenses or undergoing
surgery to flatten the cornea. However, the blinding complications
of myopia, for example, retinal detachment and myopic macular degeneration
are related to the excessive length of the eyeball. Consequently,
the methods outlined above compensate for myopia, but do not prevent
the late complications of myopia because they do not actually prevent
the excessive elongation of the eyeball that occurs in myopia.
Fact: Myopia increases
with age
Once myopia sets in, it will usually continue to increase until
the child reaches adulthood. The earlier the onset, the worse the
final outcome will be. The challenge is to either prevent myopia
from developing in the first place, or to slow down its progression.
Some common myths
Unfortunately, there are several commonly held myths which have
been around for a long time. It is important to stress that myopia
is NOT reduced by:
-
Avoiding the use of spectacles.
On the contrary, in some cases, not wearing spectacles can
lead to the development of a lazy eye, with permanent harm
done to the child's vision in the future.
- Reducing the power of the spectacles
(undercorrection).
-
Several studies have not been
able to demonstrate any beneficial effect from this strategy.
- Dietary supplements including
Vitamin A. Children should receive a balanced diet, with
adequate intake of vitamins from fruits and vegetables.
On the other hand, overdosage can cause harm.
-
Eye exercises, accupressure,
vision training. These only help to relax the eye, but they
do not shorten the eyeball or cure true myopia. However,
they are useful in inculcating good visual habits.
-
Bifocal spectacles. Several
previous studies have not shown a consistent beneficial
effect in all patients. It may have a role only in certain
children with problems of misalignment of the eyes (squints).
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Theory: The role
of Orthokeratology
This is a method which uses specially formulated rigid contact lenses
to forcibly flatten the cornea, much like braces used to straighten
teeth. However, the cornea is an elastic tissue that tends to spring
back to its original shape. Consequently, the current methods usually
provide temporary relief. We may be able in the near future to augment
this process with new drugs to achieve a more permanent flattening.
The flattening of the cornea will provide the child with clearer
vision, but it does not directly address the root of the problem,
which is the excessively long eyeball.
Theory: The role
of progressive (multifocal) spectacles
This issue has been the cause of the heated debate in the Forum
pages. There are theoretical reasons that suggest a possible role
for these spectacles. The theory is that blurred vision and/or deficient
focussing mechanisms cause myopia. These spectacles provide clear
vision for both distant and near objects even in the presence of
a deficient focussing mechanism. If this theory is true, then these
spectacles may slow down the progression of myopia.
Unfortunately, the only completed study so
far (which was conducted in Hongkong from 1991 to 1994 using a very
small set of patients) had serious design flaws which detract from
the scientific validity of the results. The case has NOT been proved
yet.
Nevertheless, this theory is attractive, and
may be correct. It is also probably harmless. Consequently, the
Singapore Eye Research Institutes has embarked on a 3 year clinical
trial to assess the effect of this treatment. All participants in
this trial are informed that we do not yet have scientific proof
that this method works. The National Institutes of Health of the
USA is sponsoring a similar trial. Results from these two trials
should be available in a few years.
Theory: The role
of rigid gas permeable contact lenses
A pilot study conducted by Dr Khoo Chong Yew, Visiting Consultant,
Singapore National Eye Centre, suggests that this might have a beneficial
effect. A definitive study is underway at the Singapore Eye Research
Institute, and the results are not available yet.
Theory: The role
of eyedrops
There has been much interest in the use of various eye drops to
control myopia for many years. One commonly used drug is Atropine.
The theory here is that Atropine acts by slowing the growth of the
eyeball, thus slowing the progression of myopia. Despite numerous
studies, this issue has not been settled either. The Singapore Eye
Research Institute has commenced a trial investigating the use of
an eye drop containing the drug Atropine. We are still recruiting
volunteers for this trial. Here again, we are careful to emphasise
that we do not yet have scientific proof that this method works
in all cases.
Myth: Myopic children
should have surgery
We have been performing laser surgery to correct myopia in adults
in Singapore since 1992. The results amongst the many thousands
of patients have generally been very good.
However, the Singapore National Eye Centre
does not believe that it is safe for children to currently undergo
this surgery. There are two main objections. Firstly, the child's
myopia is not stable, and the surgery will have to be repeated several
times as the myopia progresses. Secondly, the eyes of children tend
to have more inflammation than adult eyes in response to surgery.
Nevertheless, as further research is done, we may consider this
option when we are convinced that it is safe.
Advice to parents: All children should be screened.
The government polyclinics perform screening in infants and children
at the age of four. The School Health Service conducts annual checks
on all school children.
If you suspect a visual disorder, bring your
child to your family doctor or qualified optometrist. The eyes of
your child can be checked at any age. If they are unable to resolve
the problem, they will refer your child to an ophthalmologist.
Your child's eyes should be carefully measured
before spectacles are dispensed. Wrongly prescribed spectacles can
worsen the myopia. Sometimes, eyedrops need to be applied in order
to obtain an accurate measurement.
Control the amount of reading and near work
which your child is engaged in. Although there are onerous academic
demands, remember that your childÕs eyes will pay the penalty
in the form of worsening myopia. They should hold reading material
at least 40 cm away. There should be brief breaks after every 30
to 40 minutes.
The eye may be more susceptible to myopia development
at night. Children should sleep early, (with the lights off), and
wake up early to study.
Daily outdoor activities provide better visual
stimulation for the eyes and may be beneficial. Myopia research
requires a long time because subjects have to be followed up for
several years in order to obtain meaningful results. There are no
quick and easy answers.
Finally, critically evaluate the claims and
counter claims of vendors offering products to treat myopia. There
is NO wonder drug or treatment currently available.
For more Information on Myopia see Health Promotion Board website.
* This is a general guide.
If in doubt, please consult your doctor.
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© 2004. Singapore National Eye Centre. All rights reserved.
