Also, Lady Nerevar, it doesn't look like Vuhon and Umbra are the same. As what the book reveals, Umbra is currently powering the ingenium in Umbriel, while Vuhon is trying to find a way to no longer be a part of Vile's realm and to find the Umbra sword.
On the other hand, Vuhon says he is no longer Vuhon (though "you may still use that name, if you find it convenient."). He also displays something of a dual personality, irrationally freaking out when the sword is mentioned and then returning back to normal in the next sentence. The fact that he "powered it with Umbra" doesn't mean Umbra was completely destroyed (not something he would do if he wanted to get out of the realm), and given that Vuhon seems to have complete control over Umbriel (powered by the Ingenium), I'd say its possible that the two combined and are feeding/controlling Umbriel as one.
d'oh about the eyes. Although their color, whether black or milky white, only supports the theory that Vuhon is somehow changed.