Ashton Kutcher shares his struggle with vasculitis in a video clip released exclusively to "Access Hollywood." She was spotted at the premiere of "Revenge" on July 25 at the Ace Hotel in downtown Los Angeles.

Ashton Kutcher revealed Monday that he had been battling a severe autoimmune disease that affected his hearing, vision and ability to walk for more than a year.

"Two years ago, I had this weird, super-rare form of vasculitis," Kutcher said in an exclusive video clip released on "Access Hollywood" from an upcoming episode of National Geographic's "Running Wild with Bear Grylls: The Challenge."

"My vision was knocked out, my hearing was knocked out, all my balance was knocked out. It took me like a year to get it all back up," Kutcher told Brave and host Bear Grylls as he walked through the brambles and trees.

"You don't really appreciate it until it's gone, until you go, 'I don't know if I'll ever see again. I don't know if I'll ever hear again, I don't know if I'll ever be able to walk again,'" Kutcher said. . "I'm lucky to be alive."