Nitrates that high = bad water quality = disease
I had the same problem with nitrates.I did daily water changes of 25% for a week.I then did 33% water changes every other day for a week.Until I finally got my nitrates down to 20-30 range.
I'm now able to do 25% a week changes again.
I've never had to deal with popeye and don't know waht meds to tell you to use,but I do know the water changes will help.
If your other water parameters are close to your tank parameters then you could probably do 2 -25% changes a day.My paramters didn't allow me to do that or I would have shocked my fish.