EUGENE, Ore. — At once, dozens of Thai natives each removed a bandage from one of their eyes. In an instant, numerous people who had been blind for years, even decades, recaptured the gift of sight. For the next few minutes, tears of joy swept through the auditorium in Mae Ai, Thailand.

The previous day, Eugene ophthalmologist John Haines and his team had performed cataract surgeries for each of the patients in the same auditorium. A common medical practice that lasts just a few minutes in the United States, cataract surgery is unaffordable to many in other countries around the globe.

A few of the tears that streamed down faces that day in 2011 belonged to Haines, his wife, Joy, and the other members of their medical team.

“It’s the most emotional experience you could ever have,” Haines recalled, with a lump in his throat, this past week. “That’s the ­addictive component.”

For more than 20 years, Haines has performed free cataract surgeries — in which the eye’s cloudy lens is removed and, often, replaced with an artificial lens — to more than 2,000 patients in 11 countries. He relies on donations from lens manufacturing companies, as well as local fundraising events to pay for the costs of travel and equipment.

Born in Malaysia to Methodist missionaries, Haines, 64, has been traveling across the world his entire life. He said it was his upbringing, in fact, that motivated him to become an ophthalmologist.

“It’s the one area where, in a 10- to 15-minute operation, you can change someone’s life,” he said.

His parents’ missionary work also inspired him to help people outside of those he sees in his regular practice at The Eye Center.

“My parents instilled in me the attitude that service (provides) the greatest sense of peace, goodwill and karma,” Haines said. “I definitely got that message.”

In November, Haines will make his second trip to Myanmar for two weeks to treat some of that Southeast Asian country’s poorest residents who need their cataracts removed. He first traveled to Myanmar in December.

Haines said his goal is to provide care to those who need it most. Myanmar, according to the CIA, ranks 201 out of 228 countries in GDP per capita. Out of about 1,000 people seeking the cataract surgery, Haines’ team, which includes eight to 14 of his employees, will try to identify the neediest 200 to 250.

Several years ago, Haines’ current ambition seemed in doubt. Until 2011, a military dictatorship controlled the Burmese government. Before a planned trip to the country in 1996, Haines was warned by the U.S. State Department that a trip to Myanmar was ill-advised. As a result, Haines instead treated about 100 patients who had crossed over the border to a town named Tak in Thailand.

On a previous trip to Bulgaria, the government confiscated all of his equipment, forcing Haines to bribe officials for the return of his belongings. On other trips, government officials would hear of his “eye camps” and make sure that politically important people skipped to the front of the line.

As Haines’ flight touched down on its most recent trip to Myanmar last winter, he could not help but think that such incidents might manifest themselves again.

But through a connection with some high-ranking monks at a Buddhist hospital, Haines flew through customs with little problem.

“It’s kind of nice to have people in high places,” he said.

Once Haines and his crew arrive in Myanmar, they immediately set out to learn from a people who are just as curious about them.

“Wherever we go, they’re kind of following us around, looking at us, and questioning us,” Joy Haines said.

As a registered nurse, Joy Haines, 64, often has helped her husband with the surgery and cleaned the instruments. However, she recently has placed more of an emphasis on immersing herself in the local culture.

“I prefer to be out with the people, connecting with them,” she said.

John Haines said he receives a lot of interest from people who want to accompany him on his trips.

“There’s not a day that goes by where a patient doesn’t say to me, ‘Can I just carry your bags and go along with you?’?” he said.

However, even for members of his own practice, Haines said he can’t allow every interested person to join him. Members of his staff perform a few extra hours of work-related tasks per week to earn the right to go on the trip.

For those lucky enough to join him, the experience can be life-changing.

Before leaving the auditorium in Mae Ai, for example, the room full of impoverished, previously blind people gave the Haineses and their co-workers a gift.

“They passed a hat and came up with the equivalent of, like, $10,” John Haines said. “They said, ‘We want you to have this to help other people.”