Tang with cloudy eye

[bct15]

I just got to my brother inlaw's house to stay for spring break. He recently bought a yellow tang, probably about three inches long. It's right eye appears to be partially cloudy, and the cloudiness can be seem from the front of the fish. The lights are out and the fish does not sit still enough for pics.

Is this something normal, something that will pass or should the fish be removed and treated with furan or some sort of broad spectrum.

Thanks
Brandon