I have been trialling FL-41 tinted glasses from Axon Optics and Theraspecs, and wrote a blog post about the differences between them. Short version: They were both very soothing to look through when I had a migraine, but unfortunately I don't think they had a significant impact on my headaches. I liked the Axon Optics lenses better.
http://prettygoodpaleo.tumblr.com/post/152162067545/migraine-and-fl-41-glasses