K.B.
Could be stress reaction, sometimes with migrains this could happen (but very rare), Adie's Pupil (which is not life threating), could be a sign of diabetes, optic neuritis, Horner syndrome, sever allergy reaction (like hey fever) or just a reaction to dust or wind... same reaction could be had due to drugs, but with test done already I am sure that is not the case... maybe go to WedMD and she if type in in a few things and see what you get http://symptoms.webmd.com/symptomchecker .
Get many opnions and keep looking for answers... there is so much out there sometimes we just have to search and bring it up to the doctors and see if it is worth looking into.