A gene basic to the development of the eye may also be a factor in short-sightedness, according to a team of scientists in Guangzhou, South China's Guangdong Province.

It follows a 10-year study, which involved fitting contact lenses to the eyes of rhesus monkeys.

The gene, called pax-6, has been discovered to play an important role in the process of eye development.

"This study was to determine the mechanism leading to human short-sightedness based on the role of pax-6 in the causes of the same eye condition in infant rhesus monkeys," Ge Jian, director of Zhongshan Ophthalmic Centre under Guangzhou's Sun Yat-sen University, who leads the study, told China Daily Wednesday.

"Our study means we can reinforce the much-debated idea that most young people become short-sighted from reading too close to books or working too closely to objects such as computer screens."

According to the centre's statistics, about 70 per cent of Chinese teenagers are suffering from short-sightedness, much higher than the 6 per cent in the United States.

"But only less than 5 per cent of them are born susceptible to sight problems, with the rest being affected by the environment," Ge said.

Inspired by this phenomenon, Ge and his fellow researchers started the study on myopia in collaboration with Earth Smith and other top professors of Huston University in 1995.

Not satisfied with previous studies on flies, mice, chickens and some other animals, they decided to study rhesus monkeys, the physical structure of which is the closest to human beings.

Infant rhesus monkeys, aged from one to six weeks, wore -3.00 D glass lenses, designed for short-sightedness, over their right eyes and zero-powered lenses over their left eyes.

Ten weeks later, optically induced short-sightedness started to develop in the monkeys.

The pax-6 gene expression in the retinas of the defocused right eyes was significantly higher than in those of the left eyes.

The result suggests that pax-6 may be involved in vision-dependent eye growth, Ge said.

To induce monkeys to be shortsighted, researchers also placed contact lenses in their eyes, performed laser operations or forced them to live in small spaces for a long time, leaving them no choice but to see objects closely.

The results were similar with the first study, Ge said. All those means to induce short-sightedness in monkeys were similar with the causes of the same eye condition in human beings' short sight, he added.

The result of the study makes it more convincing that the increasing tendency of children to stay indoors watching televisions, playing computer games or reading books too closely to their eyes can cause short-sightedness.

Editor: Yan