You know... when I used to work with stage lighting a lot (every day), I would wear welding goggles or welding glasses because stage lighting is SO bright! And that was before I sustained a concussion! I literally had to look straight into the lights though to be able to tell if there was an issue.
But welding glasses might be the best "sunglasses" available for concussion survivors.
Something like these:
http://www.envirosafetyproducts.com/...d-goggles.html
But they have oodles of welding goggles available.