Size of tank in gallons or litres.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.
Are the eyes cloudy.
Are the eyes bulging out.
Is there a white rim around the outside of the eye.
Any white spots or white specs on the lens of the eye, or behind the lens of the eye.
Cloudy eye is a symtom of a disease rather than a disease in it's own right.
Causes.
Inury.
Bad water quality.
Toxins.
Stress.
Old age.
Poor diet.
Parasites.
Bacterial.