Jack Osbourne, who was Black Sabbath rocker Ozzy Osbourne, told Hello! that he suffered problems with his eyesight after shooting a scene in a lake.
"I was filming a TV show in Utah... and I had to do some scuba diving at night in a cold lake," he explained. "When I came out, I had a headache and went back to the hotel to sleep.
"The next day, the vision in my right eye started going in and out of focus. Later that evening, a black dot appeared in the same eye. When I woke up the next day the dot had turned into a cigar shape, and eventually it turned into a big blind spot in the middle of my eye."
The dad-of-one went on to describe how he made an appointment with an eye doctor as soon as he got home to LA. The doctor then referred him to the Cedars-Sinai hospital, where he was diagnosed with MS.
The former Osbournes star was given the news just two weeks after his fiancée Lisa Stelly gave birth to their baby daughter Pearl Clementine.
"The doctors are telling me I can't overly exert myself, doing things like the marathon races that I love,” he added. I know it's probably horribly selfish of myself but I'm not really accepting that."