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June 16, 2000 VOL. 29 NO. 23 | SEARCH ASIAWEEK A Picture of Progress Special lenses hold hope for myopic children By WILLIAM LAI Getting a pair is like a rite of passage for youngsters in the region. A pair of spectacles, that is. Shortsightedness is on the rise around the world (about half the global population is expected to become myopic), but nowhere more quickly than in Asia. Particularly among ethnic Chinese. Only a few begin to have trouble focusing on distant objects as toddlers. By the end of primary school, though, it's a problem for three out of five pupils in Hong Kong and half of those in Singapore. And with nine out of 10 university students in those cities having less than 20-20 vision, glasses or contact lenses are now par for the course. The picture is much the same in places like Taiwan. Which is why a Hong Kong Polytechnic University report last year spurred investigators around the world to reopen an old line of research -- into multifocal or progressive lenses. The study was small, involving only 68 children. But wearing those glasses, it seems, can significantly slow the rate of shortsightedness. During a two-year period, myopia deepened at an average rate of 123 degrees (-1.23 diopters) in children who wore ordinary glasses. Among those given progressive lenses, vision deteriorated at only half the rate of the other kids. Shortsightedness occurs when the eyeball becomes too long or the lens becomes too thick. This causes the light from faraway objects to focus in front of the retina rather than on it. Hence the blurred images. Progressive lenses act like a series of bifocals, which are graduated to give the strongest light-bending power toward the top. The idea is to enable shortsighted people to focus clearly on distant objects, while reducing the lens power when looking at something up close. Think about it: If you were mildly nearsighted, say, about -150 degrees, you wouldn't need glasses to read a book for instance. The Polytechnic University results surprised scientists because previous research failed to show significant benefit. Since then, scientists at the Singapore Eye Research Institute as well as institutions in the U.S., Taiwan and China have launched trials to assess the efficacy of multifocal lenses. Ethnicity may play a role, suggests Marion Edwards, a professor of optometry at the Polytechnic University. Earlier studies were conducted primarily on Western populations. "Progressive lenses may somehow be more effective in Chinese people," she says. Genetic factors have long been thought to contribute to shortsightedness. But investigators at the SAR's Chinese University recently eliminated a key suspect, chromosome 18, from their inquiries. The chromosome was believed to hold genes responsible for high myopia (greater than 600 degrees) in Western populations. DNA analysis of 11 Chinese families with serious shortsightedness, however, failed to find common genetic grounds. Gene sleuths deal with an enormously complex puzzle in myopia because the condition is influenced by several genes and varies among races. What's behind the rise in shortsightedness? One theory is evolution: The eye is adapting to a reduced need for good long-distance vision now that we've stopped having to hunt for food. But, increasingly, researchers believe that environment and lifestyle are more significant in the development of myopia. For instance, close to 70% of younger Hong Kong people (between 19 and 39 years) are nearsighted. Yet the condition affects only about a third of the generation above 40 years. Edwards believes this difference is due to environmental factors, though these may have greater impact on myopia in Chinese people than in other races. Take near-vision work -- tasks that require the focusing muscles in the eyes to work the hardest. These range from using the computer (whether it's for playing games or more serious pursuits) to reading and embroidery. Homework -- something that Asian children tend to get a lot of -- is another. The increase in close work could help explain why shortsightedness is more common among younger people, Edwards says. (Vision has also been found to deteriorate among Chinese factory workers who spend hours performing detailed tasks.) Shortsightedness develops fastest when children are between 7 and 10 years, says Edwards, with the condition deepening by an average of about 50 degrees a year. So a non-invasive method of slowing myopia (and therefore also guard against complications such as detached retinas) would be invaluable for these youngsters . The studies underway around the world will likely provide the final answer to the question of whether wearing multifocal lenses will help control myopia, says Edwards, who is conducting her own research. She has recruited 320 children (all with myopia of more than 150 degrees), about half of whom wear progressive lenses. The remainder use ordinary spectacles. At six-month intervals during the three-year program, Edwards' team measures the length of eyeballs and the degree of shortsightedness in each child. The results are expected to be analyzed by the end of next year. But until then, Edwards' view on multifocals remains fuzzy. Write to Asiaweek at mail@web.asiaweek.com
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