pop eye is usually caused by poor water quality and the cure is to rectify this as I understand it.
what's your tank size & reading for ammonia, nitrite, nitrate. What are the other inhabitants of the tank, what's your maintenance routine including water changes ?
If your water tests ok (0 ammonia, 0 nitrite, some nitrates) it may be a bacterial infection. I have seen maracyn 2 reccomended as a broad spectrum anti-bacterial treatment. Be sure about your water (good liquid drop test kit) before you go a-medicating.