Did you test your ammonia, nitrite, and nitrate levels? Cloudy eye is normally due to poor water quality, and so, if these aren't optimal (0 for ammonia and nitrite, under 20 for nitrate) the problem will return upon his reintroduction to the tank. Also, if you fix water quality in the main tank, you won't have to quarantine him, because the clean conditions should eliminate the symptoms. I know this isn't what you asked, but I just wanted to mention it in case you hadn't yet tested.
As for the question you actually asked (LOL) yes, you can feed him, but be aware that this is a small volume, and so you should take care not to overfeed. Possibly feed him less than usual? You don't want to stress the biological filter in the QT, resulting in poor water quality in that tank.