Blurred vision has been confirmed as the cause of James Stewart’s early exit from the Oakland 450SX Monster Energy AMA Supercross Championship main event.

In the Yoshimura Suzuki rider’s first race back following a concussion at the season opener, Stewart qualified for his second main event of the season directly from his heat race before the vision problems became apparent.

According to team manager Mike Webb, the vision issues began within the opening laps of the 20-lap main event as Stewart fell from third to seventh place before pulling off on lap eight.

“James came in feeling he was good to go,” said Webb. “He rode three days this week and put in a lot of laps, he was riding well and looked more like the old James.

“He was solid all day and did well in his heat although didn’t feel 100 percent. He got a great start in the main but after a couple laps he started to struggle with blurred vision and by lap nine he pulled off. He’s going to get some tests done early this week and we’ll see where we are then.”

Yoshimura Suzuki teammate Blake Baggett made his first appearance of the year after missing all three opening rounds with injury, he was 15th overall following a hard crash in his heat race.