It maybe too late, and unfortunately will loose sight in that eye. The best thing IMO is to treat with methylene blue. Either in your main tank or preferably in a smaller hospital tank.
Remember to take out any carbon you may have in the filter. And after a few water changes to add carbon to get rid of the rest of the blue in the water. It will be that blue when you first dose that you won't see much of your fish, but this stuff really works well.
Let me know how you get on
Good luck