The comedian, who also hosts America's "The Late Late Show with James Corden", injured his eye in 2012 but was told it had healed only to discover his sight was at risk again during a recent check-up.
"It flared up again, this little sort of scratch on my eyeball, so I've been seeing doctors a lot," he tells fellow chat show host Ellen DeGeneres. "A few weeks ago, three weeks ago or something like that, I woke up and I couldn't open my eye... It just hurt. The doctor I've been speaking with, he said, 'Look, I think we have to sort this out. I think this has been happening too many times.' "
"He took one look at my eye, and he said, 'We're gonna operate on it now.' "
Corden protested as he had a virtual show to host hours later, but his doctor assured him he wouldn't be able to work for a week.
"(He said), 'You've got to do this right now.' So right there and then, which I was quite grateful 'cause I didn't have time to dread it, they just did it."
Corden admits the surgery was strange because he was awake throughout, "It's numb, so you can't feel anything. But all the time I just kept going, 'Oh, my God, oh, my God, oh, my God!' And that was it. So, hopefully, touch wood, it's better, but we'll see."
"They clamp your eye open... and you can see what they're doing, but you can't feel it."