Herbal preventatives for migraines

I've been on 25mg of Topamax per day as a preventative for almost 10 mos now with awesome results. But now I'm starting to have problems with my eyes and I have read that this could be a side effect of the medication.

It's yet to be confirmed that my vision problems are due to the Topamax, but the more research that I do on this drug, the more that I want to get off of it.

Even though I only take a low dose and my migraines are more than cut in half, I'm not sure if the risk is worth the reward. Has anyone had any success with herbal preventatives? I'm looking for something more natural to take.