The same thing happened with me - I had a normal eye exam. It was only after a one hour vision efficiency exam that it was determined that I needed vision therapy to help me with the effects the concussion I sustained had on my vision.

I think about 1/3 of all victims of concussion are determined to need vision therapy and of those, about 90% actually benefit from it. (100% of all stroke victims who need it benefit from it.)

I think I read that studies are starting to be conducted because it is suspected that there is a correlation between vision issues cause by a concussion and prolonged PCS.