McCann had laser surgery to improve his vision following the 2007 season, and he had no problems last year. This season, he began experiencing blurry vision and dryness in the left eye during the Braves' first night game and the problem hasn't gone away.
McCann has tried different medications and eye drops, but said he won't know how much the latest treatment has helped until the Braves play Monday night in Washington.
"Day games, I'm still seeing a little blurry, but it's not like it is at nighttime," McCann said Sunday. "When I close my left eye I see fine, but when I close my right eye, things are blurry."
If the eye drops don't help, McCann might need an operation that could keep him out one to two weeks. Dryness in the eye is a side effect that has been reported by other patients who have had laser eye surgery.
"You rule out all the possibilities before you go, and getting Lasik again is a last case (scenario)," McCann said. "Who knows, it could clear up tomorrow, but at the same time it might not. It could be as early as tomorrow, or it could be as late as I don't know."
McCann, an NL All-Star the last three seasons, hit .301 with 23 homers and 87 RBIs last season. This season, he is hitting .200 with two homers and seven RBIs and has one hit in his last 20 at-bats, going 0-for-3 Saturday against the Pirates.
Because McCann is slumping, manager Bobby Cox said he wouldn't have started Sunday in Pittsburgh even if he had been healthy. David Ross filled in and hit a three-run homer during Atlanta's 11-1 victory.
"We hope he gets it resolved with these new drops. He's been trying all kinds of drops to get it calmed down," Cox said. "But we weren't going to play him anyhow because he's been struggling with the bat."