McCann went 0-for-2 with two walks in Atlanta's 4-3 loss.
After the game, McCann said he might sit out the series finale with the Nats on Wednesday to give his eye time to rest and adjust.
"It's a process," McCann said.
McCann went to an eye doctor in Washington on Tuesday morning who gave him a contact lens that initially appears to have taken care of the problem. The catcher had Lasik surgery at the end of the 2007 season and said his vision has changed slightly since then but there's no need for any more procedures.
Before going out to batting practice, McCann said his eye felt much better.
"I put the contact in, and it clears it up right away," McCann said. "I'm seeing good. It's a big relief. You know kind of why you've been blurry for the past couple of weeks."
McCann said the problem had been causing him a lot of worry because of its uncertainty.
"Now I just have to move on," McCann said. "There's no thinking [that] it could be this, could be that. Now I know what it is."
Braves manager Bobby Cox put his starting catcher in the cleanup spot and made the final decision after seeing how the catcher did in batting practice.
"He says he sees perfectly today," Cox said before the game. "It's just about driven him crazy for a couple of weeks now. We're not going to let him go out there unless he's 100 percent."
McCann said he's battled eye problems since the eighth grade and that the Lasik surgery was the best thing he ever did. He saw great last year and hopes that the contact lens will work out and resolve the problem.
Cox said he also was hopeful for a solution. McCann did a number of things in recent days to fight the problem but nothing worked well.
He started using an antibiotic ointment over the weekend, but that increased the blurred vision and kept him from starting the final game in Pittsburgh on Sunday and the first game against the Nationals on Monday.
In addition, McCann started using drops at least six times a day because his eye began to feel dry. But that didn't help much either.
Jeff Seidel is a contributer for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.