Nitrate? Water change schedule? How much LR in there? Sump? Skimmer? Tank mates?
Cloudy eye is usually a result of poor water quality.
If what you have is actually black ich, it is fairly easy to get rid of and can, although not recommended, be treated for in the display tank. Black ich, unlike cryptocaryon, is actually a worm and therefore is best treated with praziquantel for which most hobbyists use the retail product praziopro. Praziopro is probably the most gentile of the medicines we use, and fish tolerate it well.
You have two options. You can remove all fish and treat them with prazipro in a hospital tank(s) and leave the display fallow for at least 8 weeks. Alternatively, you can treat the display with prazipro, and virtually all inverts and most corals will tolerate the treatment, but some corals and inverts particularlly sensitive could be at risk, although most report no problems. The medicine will not be absorbed in calcerous substances, like rock or sand, and is easilty removed. Whichever approach you adopt, I would treat in the prescibed amount except break up dosing into two successive 1/2 doses spaced one day apart instead of one dose in single day and treat for 5 days after second dose. I would then do a large water change and treat again if also treating in the display. Otherwise, second treatment is optional in hospital tank.
When treating a system, no skimmng or carbon. Also, limit the light (duration and intensity) the best you can for the first 24 hours after dosing because medicine is photosensitive and breaks down in strong light. When you want to remove the medicine from the display, use the combination of a large water change, skimming, and activated carbon.
