Anatomic oculomotor deviation: (diopters, prism convergence units) This test measures the eyes' natural deviation (heterophoria) and also allows the detection of strabismus. In strabismus, anatomic deviation is evident and the person's dominant eye is looking at you, but the "lazy/deviated" eye is not. In heterophoria anatomic deviation is not visible to the naked eye and the deviation has to be triggered by covering in sequence, one eye at a time, to trigger the deviation. There are two identical tests: one occurs with an object placed at 3m from the seated participant (far vision), and the other with an object at 30cm from the seated participant (near vision). In this test, seated participants focus on an object. These movements can be seen by the clinician. The clinician covers/uncovers eyes to trigger movements and uses a prism to cancel the movement. The prism that achieves this cancellation is the measure of anatomic deviation. The rating of the prism that achieves this cancellation is considered the score for this test, with one score for the object placed at 3m and another score for the object placed at 30cm. Participants with strabismus are excluded in our study because strabismus is a contra-indication to post-concussion visual training, which is part of our larger study and thus, patients with strabismus do not represent our target population.