There are often various symptoms of vision problems. Over my years of practice, I've come across a certain type of patient who has trouble using their eyes together. In addition to having problems with reading including loss of place, fatigue and headaches, the is one more symptom. They have motion sickness when sitting in the back seat of a car. What's interesting is that there's often significantly less motion sickness when driving in the front seat of a car and almost no problem when driving. I equate this to that there's more visual processing in the back seat where you see things off to the side, things two feet away and things at distance. In the front seat you only notice basically things in front of you far away and when driving, you have tactual back up (with holding the steering wheel) to the vision.