My alfie had the same thing, it's a cataract, however he was already blind, they live fine, just talk to make sure they know you're coming and give them extra treats and attention.
Alfie lived a year after he got his, and it wasn't associated with his death, so they live fine with them.
Alfies took up most of his eye, making it all white, if it's smaller it might be an injury, but most likely just a cataract
hope he's doing ok!