Jack Osbourne has said the toughest thing about having multiple sclerosis is that "it's a completely unpredictable disease".
Appearing on American daytime show The Talk, which is co-hosted by his mother Sharon, Jack discussed what it was like losing the sight in one of his eyes.
"Ultimately that is 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," he said.
He added: "It's back to about 80 per cent now. They don't know if it will ever improve beyond that, but everyone's different."
Jack first went public with the news of his health in an interview with People magazine.
Multiple sclerosis attacks the brain and spinal cord, and can cause somewhat mild problems or serious disability, such as paralysis.