cloudy eyes in fish can have many causes including velvet, Ich, fish tuberculosis, corneal edema, cataracts, nutritional deficiency, bacterial infections, fungus, or on rare occasions digenetic flukes such as Diplostomum. trauma and hereditary factors can also be causative.
in the vast majority of cases however, water quality is the issue so get your water insto pristine condition and you may find this problem resolve on its own.