Did the "medical waiver" thing last time I went to my eye doctor for a new prescription. Just brought the form and told her that tint helped me drive with less light irritation. I already had tint by this point obviously. She signed it without question and I faxed the form in, had a new registration in less than a week.
New reg is the same, just says "sunshading" at the bottom. I carry the signed form as well with my Dr's signature just to be safe.
2010 335i xdrive M sport - Sold