Wow strange, I had one of my neons lose an eye this weekend too!
Unfortunatly I was a bit too late, he was upside down hiding underneath the branch of a plant
Oooohhh!! That would also explain why 1 of my 2 is smaller and has no bristles. Bought them both when they were just babies. Has anyone ever taken them out of the tank and had them in a bucket while doing an overhaul? Try to tip them back in and they're still in the bucket with no water in it hahaha.