This is something that, so far, Chinese people have had to live with. But now scientists at the Chinese University of Hong Kong believe they have isolated a genetic structure inside human chromosomes that could be the cause of myopia. And they believe that, by understanding what causes bad eyesight in Chinese people, this could, over time, help to reduce or eliminate the scope of the problem.

Scientists began their research as the population of myopia sufferers grew rapidly in the past decades in Asian places where Chinese people are the main inhabitants.

They began to wonder what caused the condition and why Chinese people seem to be more prone to it. And the research team from the Chinese University, worried by the trend, started looking at young sufferers of myopia.

Already, five per cent of kindergarten pupils surveyed by the team last year have myopia, and the number of sufferers grows with age.

In the group of primary six, about 60 per cent of the students are near-sighted. The situation worsened for secondary school students, of whom 75 per cent are myopia sufferers. And among the university students, only 10 per cent were spared from the condition.

'The results are quite worrying,' said Dr Dorothy Fan Shu-ping, assistant professor at the Department of Ophthalmology and Visual Sciences at the Chinese University.

'There are more myopic people in Asia than anywhere in the world. It is also related to the education level of sufferers . . . if only precautions had been taken at an early stage,' she said.

Most children start to develop myopia around the age of seven, although it has been observed as early as two. Their eyeball becomes too long or the cornea too curved, causing the light rays from distant objects to converge before they get to the retina, which tells the brain what the eye is seeing. The retina sends confused signals to the brain blurring the image that a myopic sufferer sees.

While the main cause of myopia is still unknown, scientists all over the world have pointed to gene factors which interact with the environment to cause myopia.

Dr Fan and her colleagues at the Chinese University have spent the past three years looking into the issue. Although handicapped by limited resources, the team recently located an area inside chromosome 18, where the myopia-related genes are said to exist. But the team believes it is still at least five years away from identifying which genes are responsible.

Professor Marion Edwards, of the Department of Optometry and Radiography at the Hong Kong Polytechnic University, is another pioneer in the research into myopia in Hong Kong. She believes the environment plays an important role in contributing to myopia, citing the university's studies that there are more young myopes nowadays than in their parents' generation.

The results coincide with that of a North American study among Eskimo families. This found that, while myopia was almost unknown among parents, who never went to school and spent little time reading, it was highly prevalent among their children.

'Such a widespread change, over a few generations, cannot be due to genetic mutation,' Professor Edwards said.

'The higher prevalence of myopia in certain racial groups suggests that myopia in these races may, at least partially, be due to a genetically determined susceptibility to some environmental factor.' Professor Edwards said intensive school-work and reading of Hong Kong students was part of the environmental factor, and teachers should encourage students to look into the distance from time to time.

Without knowing the main cause of myopia, the best that can be done is to take preventive actions and stop it from progressing.

'It is essential that parents pay more attention to their children's seeing ability and make corrections when the child is young,' Dr Fan said.

'Regular checks by covering one eye will help the parents tell if their children can see properly. It will also help in early diagnosis of other conditions such as a squint and lazy eye.' Kindergarten pupil Wong Wae-si is no stranger to eye checks since she was diagnosed as a myope of 400 degrees last year, when she was only three years old.

Her condition escalated quickly to 800 degrees within a year, and she must now keep her glasses on until she goes to sleep. This is to reduce the strain that may be exerted on her eye muscles when she tries to look at objects more than 18 centimetres away.

HER mother, Wong Chiu Kit-yuk, 32, said the strong myopia of her daughter was a puzzle to the family, which does not have any relatives who are sufferers.

And her second daughter, at 1.5 years old, has normal eyesight.

Mrs Wong suspected she did not take enough vitamin pills when she was pregnant with Wae-si, but doctors could not give a definite explanation.

At just about 18 months, Wae-si was already showing signs of problems, recalled Mrs Wong. They included a lack of concentration, being insecure, impatient and fretful, she said.

'It is rare for a three-year-old not to like watching TV, but she rejected it so much that every time we turned it on, she would cry and demand it be turned off.

'She did not like hearing the sound without being able to see clearly.' However, five-year-old Tan Yuk-shing was so quiet about the distorted images that his parents did not know he already had myopia of 900 degrees until he was diagnosed for the first time at 3.5.

His mother, Tan Tsoi Siu-kwan, 33, said the boy was taken to a public clinic for eye tests after he was seen sitting close to the TV to watch with his eyes squeezed, but was told that there was no problem.

It was not until she took him to a private clinic that the serious myopia was confirmed.

'He had lived with blurred images for a long time without knowing what happened to him. Now he doesn't want to take his glasses off,' Mrs Tan said.

Children before puberty may develop myopia at a faster pace as their eyeballs are still growing.

Spectacles and corrective contact lenses worn at night are said to be effective in controlling the progress. There are also other techniques such as laser surgery, which is more suitable for adults with extreme myopia.

Most optometrists agree that six out of 10 children may need to wear glasses, but the standard of optometrists in Hong Kong is a matter of concern, as many of them learned the skills without formal qualification.

It was only in recent years that the opticians, who measure short-sightedness and prescribe glasses for customers at retail shops, were required to get some sort of qualification.

Even so, more than half of the 2,000 optometrists in Hong Kong are now working with only a temporary licence as the Government has not set a deadline for them to qualify.