Impatiently, Gopur Samat stood at the ready as a nurse stripped the bandage from his right eye and steered his attention toward a chart 20 feet away. Smiling, Samat pointed up. Still smiling as the nurse gestured toward another symbol, he pointed down. Then left, then right. Samat, 68, suddenly could see clearly again.

"Now I will be able to read," he said, drawing up plans to resume studying the Koran and Islamic religious works when he returned to his farming village in the vast flatlands of China's Xinjiang province.

The operation that restored sight to Samat's right eye has been repeated more than 50 times a day in recent weeks aboard an extraordinary train, the Lifeline Express, that has pulled onto a shunting spur on the outskirts of this remote and history-laden city 2,000 miles from Beijing in the shade of the snow-covered peaks of far northwestern China.

The train, the brainchild of a Hong Kong accounting executive, is one of three that chug across China as mobile operating rooms, bringing skilled Beijing specialists to perform free cataract operations for poor peasants who cannot afford the 15- to 20-minute procedure needed to peel away the clouded lenses blocking their vision. Aboard the Express, two doctors perform the operations 10 to 12 hours a day, treating one patient after another in an assembly line of life-altering moments for China's least-favored people.

The operation, although simple by today's standards, is no small thing in a country where, according to Health Ministry statistics, 4 million people have cataracts. Unlike in most other countries, the cataract-stricken in China include a high number of children -- sons and daughters of poor farmers who work the soil around primitive villages far from the glistening skyscrapers of China's modern cities.

Nobody has figured out for sure why so many Chinese peasants and their children develop cataracts. Some doctors have speculated that the condition is congenital, related to the fact that farmers in isolated villages often marry their cousins. Others have suggested that the way mothers carry their babies while working in the fields -- in slings on their backs -- forces the infants to look up at the sun for hours at a time. Research is underway, but in the meantime, operations to replace damaged lenses remain the only way affected people can get their eyesight back.

Since the first Lifeline Express pulled out of the station seven years ago, tens of thousands of cataract patients, many of them children, have had their sight restored in 44 backcountry localities salted across 18 of China's 34 provinces. Each of the three trains costs about $1 million a year to operate, with funds coming from a Hong Kong-based charity called the Lifeline Express Foundation.

Nellie Fong, chairman of China operations for PricewaterhouseCoopers, said she got the idea for Lifeline Express while serving on a committee preparing for Hong Kong's return to Chinese sovereignty in 1997. Hong Kong was receiving congratulatory gifts from across China, she said, and business executives wanted to make the gesture of giving something in return.

After hearing of a medical train in India operated by the Tata group, that country's second-largest business conglomerate, Fong went to the Chinese Health Ministry with her suggestion for a similar project here. She said ministry officials urged her to focus on cataract patients in China's poorest regions, where hospitals often do not have the expertise and equipment to perform cataract removals and peasants do not have the money to pay even if they did.

Fong agreed, realizing that cataract operations would produce immediate results that would aid in fundraising. "The impact of helping a blind person see again is one of the biggest things you can give," she said.

Liu Jing, 39, a doctor from Beijing Railway Hospital who volunteered to work on one of the trains for a year, said the heavy workload, the regimented life aboard and the long separation from her husband and 13-year-old son are offset by the immediate gratification of restoring sight to blind or half-blind peasants.

"It's very tiring, really," she said during a lunch break in the dining car. "But when they get their sight back, the people are so happy, and that makes us happy, too. So it's worth it. It's the height of satisfaction to heal people."

The operation involves cutting into the cornea and removing the clouded lens with an ultra-thin suction device, then replacing it with an artificial lens. With adults, it can be performed with local anesthesia, although children must be rendered unconscious lest they wiggle.

Marcia Aw, a Hong Kong fundraiser for the foundation, said Beijing's ophthalmologists compete for positions on the trains despite the hardship. Well-known specialists regularly visit to share their techniques, she explained, and the doctors return from their year aboard as veterans with about 10,000 cataract operations under their belts. Also, the Health Ministry in Beijing has agreed to continue paying their salaries during their year on the train.

Liu Li, 45, another doctor from Beijing Railway Hospital, said that with that in mind, her husband, also a doctor, supported her decision to volunteer despite the separation from him and their 17-year-old son. Family support, along with skill, is one of the criteria used to select doctors from the list of volunteers put forward by Beijing hospitals, Aw said.

Local and provincial health departments are also enlisted to help, providing electricity and other utilities at each stop and bringing patients to the train in an orderly, pre-screened lineup from villages often scattered across a wide area. Gul Nisa, who runs Kashgar's health services, said she and her staff spent four months organizing transport and pre-op examinations for those filing through the Kashgar train.

Kurbniyaz Tohti, 70, said he was brought in from a wheat-farming village 180 miles south of Kashgar after being told of the train's visit by local health officials. Stricken three years ago by a cataract in his left eye, Tohti jumped at the chance, he said, because he was having more and more trouble seeing his four children and 16 grandchildren.

"A lot of new things are coming up every day," added Tohti, who sported a wispy gray chin beard characteristic of the elderly among Xinjiang's mostly Muslim Uyghur people. "I would like to get my eyesight back to see them all." Twenty-four hours later, he had, and was resting in a bunk in the train's 52-bed recovery room car.

In a nearby bunk, Mangsur Aysa, 72, a farmer from Yarkand, 150 miles south of Kashgar, wept at the thought that his long-clouded left eye would be clear. "I'm so happy," he said, turning his face to hide the tears that still fell onto his wizened cheeks an hour after his surgery.

The next morning, he was in line with Samat, waiting his turn to have his bandage removed and read the eye chart.

Fong said fundraising for Lifeline Express traditionally has concentrated on Hong Kong's wealthy individuals and big corporations. But with mainland China sprouting its own millionaires, and with a 100 percent tax write-off for charitable donations a part of Chinese law, the foundation has moved to seek money in Shanghai and Beijing.

The latest mainland fundraising strategy was worked out last month with China Mobile, which handles calls for about 85 percent of China's 200 million cell phone users. Under the arrangement, customers can donate by sending a text message to China Mobile, which puts the donation on their phone bill and relays the money to Lifeline Express.

Gopur Samat, 68, takes a vision test aboard the Lifeline Express after his surgery. "Now I will be able to read," he said.Liu Li, 45, a Beijing doctor, volunteered to spend a year performing operations aboard the train. Her work keeps her apart from her family.