Jack Osbourne struggling with the uncertainty of MS

Reality star Jack Osbourne is struggling to cope with the uncertainty of his multiple sclerosis diagnosis, insisting he is terrified by the "completely unpredictable" nature of the illness.

Rocker Ozzy Osbourne's son consulted a doctor after experiencing blurred eyesight and headaches, and was told he had the autoimmune disease last month.

Opening up about his condition on U.S. TV show The Talk, the 26 year old admits his vision has improved but he still worries his health could deteriorate at any moment.

He explains, "(My vision) is back to about 80 per cent now and they don't know if it'll ever improve beyond that but everyone's different. There was a point where they didn't know (if it would return but) it will return to some capacity but everybody's different. Some people are left with a blind spot, some people return 100 per cent, some people never even get anything back. It's really hit or miss...

"Honestly, I'm fine. Ultimately, that's the toughest thing with this disease that I'm learning... One minute you can be fine, and the next I went blind in my right eye. It's a completely unpredictable disease."

Osbourne was joined on the chat show on Wednesday by his fiancee Lisa Stelly, who credited their two-month-old daughter Pearl with keeping his problems in perspective.

She says, "We are really trying to stay positive. We have diapers to change and a little girl to look at and smile at."