In reply to pasbury:
My mum uses them and she reckons they work, She just puts it on on a shelf just out of/behind her field of view while eating breakfast so that it feels like you are sat next to a bright window. This anecdotal evidence is't worth much scientifically but I'm not sure how you could do a double blind test for such things and if the effect is that you feel better then that's what you wanted anyhow.
My friend who went to Aberdeen university said that they were available to borrow from the university, which makes you think that there is some validity to their claims.
They are quite cheap these days so it's worth a pop (obviously following health warnings if you have anything like epilepsy).