The cloudy eye could be a result of the recent unstable water parameters.
The tang's immune system is stressed/compromised from the recent move to a new tank,
unstable water parameters and a potential injury and possible bacterial infection.
I would focus on pristine water conditions to try to decrease stress.
I would enrich the food with beta glucan, selcon and vitamins to boost the immune system.
In light of the fact of recent stressors, possible injury versus bacterial infection and now a cloudy eye
- you could be conservative - focus on water quality, decreasing stress and feeding enriched food.
Or you could be aggressive and do everything in the "conservative approach as well as adding antibiotics.
For antibiotics, I use maracyn - 2, kanamycin and nitrofurazone.
Jungle has a medicated food "Anti-Bacteria" that contains nitrofurazone and sulfa.
When feeding medicated food - only feed the medicated food as to make sure the fish gets enough antibiotics.
If you opt for antibiotics, you must treat for 7 - 10 days even if the symptoms disappear,
so you do not partially treat and run the risk of the bacteria developing a resistance to the antibiotics and redeveloping.
Please provide updates... Good Luck!