Myopia, or difficulty in seeing far, is the most common optical disorder
in the world and usually develops in childhood.
I MADE an interesting observation when I was teaching a group of medical students this week. Out of the class of 20 students, 75% of them were wearing spectacles or contact lenses for myopia!
It may be a simple survey of a select group of people but it highlights the point that myopia is increasing not only in Malaysia, but also in the rest of the world. There is no simple answer as to why myopia rates are increasing and I hope to enlighten you with the latest research in this area.
Myopia, or difficulty in seeing far, is the most common optical disorder in the world and usually develops in childhood. This is usually due to abnormal elongation of the eyeball, which causes images to be focused in front of the retina instead of directly on to the retina. This requires optical correction aids like spectacles or contact lenses to correct for this abnormal focus.
Myopia is a major cause of adult blindness, especially in patients with higher degrees of myopia (pathological myopia). There is also a huge economic burden to the world. More than one billion people worldwide are myopic and using a conservative estimate of US$50 (RM150) per person spent on spectacles annually, this adds up to US$45bil (RM13.5bil) a year spent on optical care alone.
It is estimated that in countries like Singapore, Hong Kong, and Taiwan, almost 75% of the population suffers from myopia.
In Malaysia that figure is on the increase. In 2003, a survey of more than 4,000 schoolchildren in Gombak showed that 35% of them were myopic. Among the 15-year-old age group, myopia was more common in Chinese (65%), followed by Malays (30%), and Indians (16%).
It is hard to say for sure how much more our population has become myopic now compared to 30 years ago as such surveys were not done then. However, a simple unscientific comparison of class photos of my Standard One class 30 years ago and my daughter’s class photo today shows that there are many more children wearing glasses today.
Why are myopia rates increasing?
There is evidence to suggest that being of Oriental race (Chinese, Korean, Japanese), or if your parents are myopic, increases your chance of being myopic. The main cause of myopia is the environment that we live in. People who live in countries with the highest myopia rates in the world like Singapore, Hong Kong, and Japan, live in a dense urban environment with little outdoor space.
Compare this with the Eskimos who live in a harsh outdoor environment, and they have the lowest myopia rates in the world.
What is interesting is that while myopia rates are low in countries like India (20%), myopia is higher in the Indian population in Malaysia and even higher again in the Indian population of Singapore. This suggests that people of Chinese, Indian, or Malay origin respond to the environment they live in with an increased prevalence of myopia.
Certain activities like excessive near work can lead you to develop myopia. In Singapore, there was a significant association found between the degree of myopia and the number of books read per week in school children. Reading more than two books per week makes you three times more likely to develop myopia. Children who read continuously for more than 30 minutes were 1.5 times more likely to develop myopia.
This is probably also true for children who play too many hand-held computer games!
Lower amounts of sports and outdoor activities increases the risk of children having myopia. A recent study compared similar-aged Chinese children in Singapore and Sydney, and looked at many things the children did – such as reading, diet and outdoor activities – and tried to correlate it with rates of myopia in each city.
Interestingly, although Chinese children in Sydney performed more near work than Chinese children in Singapore, the Sydney children had lower rates of myopia. This was thought to be due to the increased time spent outdoors.
Exposure to different wavelengths of light can induce myopia. Experiments done on baby chicks showed that when exposed to predominantly red light, the chicks developed myopia, while when these same chicks were exposed to predominantly blue light later, the myopia became less.
As our indoor environment is dominated by longer red wavelength light while the outdoors have more shorter blue wavelength light, this suggest a protective effect of outdoor light exposure on myopia. However, we also have to remember that excessive UV light exposure outdoors may be damaging to our retina and skin, so we should consider wearing sunglasses and put on sun block lotion when exposed to direct sunlight.
What are the problems associated with myopia?
Myopia is not a trivial problem. People with high degrees of myopia of more than -6.00 dioptres (power of 600 in layman’s terms) are defined as having pathological myopia. Patients with myopia have a longer eyeball length than normal and this means that the retina is stretched inside the eye. This causes higher risk of developing serious eye conditions like retinal detachment, macular hole and macular degeneration.
Myopic patients are at higher risk of getting glaucoma and cataracts at a younger age. This can all lead to a lower quality of life.
Can myopia be cured?
Unfortunately, there is no cure for myopia. Refractive surgery like LASIK only treats the front of your eye (cornea) to correct for the myopia so you don’t need to wear glasses. The rest of the eye is still abnormal and your risk of cataract, retinal detachment and glaucoma remains as high as before you have refractive surgery. Therefore, prevention of myopia remains the best public health approach.
What can we do to prevent myopia?
Many types of therapies have been suggested to prevent myopia, such as bifocal glasses, wide rim glasses with different focal lengths, wearing rigid gas permeable contact lenses overnight to reshape your cornea, and visual training.
There are many ongoing studies looking at those therapies and it is debatable whether they are effective or not. Most eye doctors would not recommend that children wear contact lenses in their eyes overnight as it carries the risk of serious eye infection that could affect the eyesight permanently.
Currently, the only therapy that has been shown to be effective in large randomised controlled trials is atropine eye drops. A study done in Singapore has showed that dilating the pupil with atropine in children is effective in retarding the progress of myopia.
However, there are side effects from the eye drops, such as blurring of vision for near work, glare when outdoors, and children having to wear reading glasses. We do not know how long we need to use these drops for, and how often to use them.
As such, the use of atropine is still limited in slowing down myopia progression as this drug can have serious side effects.
There is no evidence that any particular supplement or diet can cure or prevent myopia. Therefore, prophylactic consumption of any carotenoid-rich supplement is not only unnecessary, but you risk overdosing on fat-soluble vitamins which are not so easily excreted from the body when taken in excess!
Probably my best advice for now is to take the evidence from the Sydney myopia studies which showed that children who did more outdoor activities had lower rates of myopia. Encourage your kids to play outdoors regularly and spend less time reading or playing computer games.
Myopia appears to be predominantly caused by our modern environment. While the rates in Malaysia are not as alarming as in Singapore, our population’s eyesight will become more and more myopic as the living environment becomes more urbanised with less outdoor open spaces.
Myopia is also made worse by our society which places too much emphasis on academic achievement which, in turn, forces our children to do excessive near work and have no time to play and exercise outdoors.
Dr Fong Choong Sian is a consultant ophthalmologist while Goo Chui Hoong is a consultant dietitian. They are publishing a book on eye health and diet next year. For further information, e-mail email@example.com. The information provided is for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this column. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.