One of the boys in my learning study has had constant headaches as well as blurry vision making it difficult for him to navigate tracking from the blackboard to his desk affecting the physical act of reading. After several sessions, he has reported very few headaches. He also said that when we first started, he would have blurry eyes after reading about 5 minutes. Last time I asked he was up to about 25 to 30 minutes. My goal is for him to not get blurry eyes when reading.
Two things stand out from our testing: we found plenty of injuries to the bones in the head and upper neck and there are plenty of spinal cord injuries in the upper neck especially related to the dura mater - the outside layer of the spinal cord.