In a recent episode of National Geographic's 'Running Wild With Bear Grylls: The Challenge', Ashton Kutcher shared details of his struggles after being diagnosed with 'vasuculitis' — a rare disease that took around a year to recover from.

The father of two appeared on the often stressful survival show alongside Bear Grylls and began discussing both the mental and physical strain he endured after being diagnosed with vasuclitis — an autoimmune disease wherein blood vessels become inflamed.

Having had a "super rare form" of the disease, Kutcher experienced loss of both his hearing and vision for an extensive period of time. He shared "Like two years ago I had a weird, super-rare form of vasculitis that knocked out my vision, knocked out my hearing and knocked out all my equilibrium".

He explains the mental struggle with uncertainty that he encountered at the time, wondering whether he'd ever be able to regain this functioning, "I don’t know if I’m ever going to be able to see again; I don’t know if I’m ever going to be able to hear again; I don’t know if I’m ever going to be able to walk again".

From the sounds of things, Kutcher seems to be grateful to be back in action and filming for projects like the reboot of 'That '70s Show'. Of his decision to return alongside wife Mila Kunis, Kutcher explains "Listen, we’re only in the position that we’re in because of that show, so let’s just go back and do this".

Watch a clip from Kutcher's appearance on 'Running Wild with Bear Grylls: The Challenge'.