If both eyes are cloudy then I would say water quality is most likely the cause, If it is in one eye then it could be the result of an injury. Either way do a water change and keep up the water quality to speed healing. You can soak the food in garlic, which will help, but it is not a cure. I would also vary his diet, get some fresh raw squid, shrimp, and scallop from the grocery store, and soak the food in a small amount of tank water and garlic, also add vitamins such as selcon.
In addition to this you can treat the tank with melafix, it is an all natural product that I have had success with in the past. It is reef and invert safe, just remove your carbon, and turn off the skimmer and UV if you have them. It usally clears up the cloudy eye after 7 days.
Good Luck
