Three years ago, a cornea from Sri Lanka restored Xu Pengfei's sight in his right eye, and on Wednesday the 10-year-old was able to express his thanks by helping someone in Sri Lanka see again.

On Wednesday, Xu and a Chinese doctor together removed the bandages on the eyes of Sudarma Karunaratna, a 74-year-old English teacher, after she had cataract surgery on her right eye at a hospital in Colombo, capital of Sri Lanka.

Karunaratna is one of 500 patients who have received free surgeries from Chinese doctors in the past four days and recovered their eyesight.

In the next few days, the Chinese medical team will perform a further 500 surgeries, according to Yao Xiaoming, a leader of the medical team.

The project was organized by the Chinese embassy to reciprocate 1,500 cornea donations by Sri Lankan locals to Chinese patients.

The activity coincides with President Xi Jinping's visit to Sri Lanka, the first state visit to the country by a Chinese head of state in decades.

"Thank you, people of Sri Lanka," Xu, the boy, said on Wednesday, adding he was grateful for the unknown Sri Lankan cornea donor who gave him sight.

First lady Peng Liyuan, who also witnessed the recovery of Karunaratna on Wednesday, gave Xu a hug and encouraged him to have confidence in life.

She thanked Sri Lanka for donating 10 more corneas. Sri Lanka's donations of corneas and China's offer of cataract surgeries not only restore eyesight for patients, but also build bonds between the two peoples, she said.

She donated equipment for conducting cataract surgeries to Sri Lanka, encouraging the two sides to continue the project and deepen the friendship.

Although the population of Sri Lanka is only 20 million, it is one of the world's largest cornea providers. It donates thousands of corneas a year to 57 countries and regions. The country has donated more than 1,000 corneas to China.

Sri Lankan President Mahinda Rajapaksa gave two corneas as gifts to China when he visited China in 2007.

In China, the available transplant corneas fall far short of demand. More than 3 million patients wait for cornea transplant surgery every year, and only 5,000 of them receive corneas, according to Xiamen Eye Center of Xiamen University, which sent three eye experts to Colombo for the project.

Contact the writers at wujiao@chinadaily.com.cn and wangxiaodong@chinadaily.com.cn

Shan Juan contributed to this story.