From what I've read, there is no conclusive evidence to show that a decrease in your lipid profile will result in an improvement in xanthelasma. There are always surgical options, but right now that's about it. The key thing to remember is that xanthelasma is a POSSIBLE sign of high cholesterol and requires monitoring. Xanthelasmas are a marker for atherosclerosis, especially in the carotid arteries in the neck.
Sorry, I'm sure you were hoping for a different answer. Perhaps someone who is more knowledgeable than myself with these will post more information.
I was not expecting a different answer. I was expecting a corroboration. My idea mathes with your information.