SANTA CLARA – Alex Smith said Wednesday he tried to "blink off" the vision problems that started to affect him in the second quarter of Sunday's game against the Rams. But the 49ers quarterback said the issues only got worse, and he soon realized he'd be of no value to his team.

"It's tough to play quarterback without your eyes," Smith said after taking part in a noncontact practice. " … All of a sudden, there was a bunch of things out there that I couldn't make out. I just felt like I couldn't help the team out there."

Smith said the concussion symptoms he suffered Sunday, especially blurry vision, were similar to what he felt after a Week 2 game against the Cowboys last year when he also was diagnosed with a concussion. Smith played in the following game last season.

But this week's episode has been more severe, Smith said, and the symptoms also included headaches and nausea. "Last year was not even close to this," he said.

Still, Smith seems on track to play Monday night against the Chicago Bears. He's passed all of the post-concussion parameters set by the league, including being cleared by the Stanford Hospital neurologist he saw Monday.

Smith was dressed in a black, no-contact jersey Wednesday, taking snaps with the first-team offensive line and throwing passes to Michael Crabtree and the team's top receivers. The final hurdle is being cleared for a full-contact practice session, which could happen as early as today.

"I feel good," Smith said. "I felt good (Wednesday). Everything I've kind of gone through, I've felt good. It's really not up to me, though. It's a better question for the doctors. They have a lot of stuff they're looking at. I'm not even sure what my answers are telling them, though."

Smith's teammates said they were prepared to face the Bears' opportunistic defense with either Smith or backup Colin Kaepernick, who relieved Smith midway through the second quarter and led the 49ers on a last-minute drive that tied the score in regulation.

Tight end Vernon Davis, however, said he suspected Smith would play.

"He looked pretty good to me," Davis said of Smith's practice. "Looked like he was ready to go. And I think with that game being on Monday, he'll have a little bit more time."

Smith said his vision started to blur following a second-quarter quarterback sneak in which he dived head-first into a pile of players. He acknowledged, however, that a hit by Rams linebacker Jo-Lonn Dunbar six plays earlier could have contributed to his problems.

Smith was staggered after the blow, and team physicians checked him for signs of a concussion between the first and second quarter.

"It's all kind of speculation. It (the blow) certainly didn't help," Smith said. "It certainly, in talking to the neurologist, probably contributed for sure. Whether it kind of loosened you up and primed you for the next (hit) that's not as big – don't know.

"I felt fine after that, though. I definitely knew I took a big hit, but vision and as far as anything like that I felt fine. But the sneak, definitely when I came up after the sneak is when my eyesight was kind of first gone wrong."

Smith was sharp following the quarterback sneak, completing three passes, including his longest of the game – 19 yards – to Crabtree and a touchdown to Crabtree.

How was he able to do that with deteriorating vision?

"It's a great question," Smith said. "I have no idea."

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