After Osbourne experienced 60% vision loss in his right eye earlier this year, he underwent a series of tests to determine the cause.
Multiple sclerosis affects the central nervous system, but its symptoms and their severity vary. According to the BBC, "one in five sufferers has a benign form with mild attacks and no permanent disability, while another 15% have a progressive disease that steadily worsens."
Symptoms range from loss of muscle control to cognitive disability, and may subside or develop into permanent problems.
His parents have taken a more introspective approach to the news. "I kept thinking: 'What did I do wrong, what did I eat or drink when I was pregnant?' I feel like it's somehow my fault," Sharon Osbourne is quoted as saying. "If it was me, you'd think: 'Ozzy had a reputation and it caught up with him', but Jack is such a good guy," said the legendary Black Sabbath frontman.
[photo via Getty]