BEIJING — It started this week with a call to action from China’s leader, Xi Jinping. Too many of the country’s children need glasses, he said, and the government was going to do something about it.

It ended on Friday with billions of dollars being wiped from the market value of the world’s largest video game company.

New controls on online games were among Chinese authorities’ recommendations for reducing adolescent nearsightedness on Thursday, sending shares in the country’s leading game publisher, Tencent, tumbling the next day. Shares of Japanese game makers like Capcom, Konami and Bandai Namco also fell on Friday, a sign of the size and importance of the Chinese market.

The sell-off is the latest in a series of government-related stumbles for Tencent, one of the world’s largest technology companies. Chinese state media has blamed video games for causing young people to become addicted, lowering their grades and worse. An episode last year, in which a 17-year-old in the southern city of Guangzhou died after playing a smartphone game for 40 hours straight, received wide attention.