This 26-year-old man presented with complaints of intermittent visual disturbance that he describes as “shaking and tilted vision”. This happens variably from as often as every day, sometimes only a few times a week, and usually lasts a few seconds to a few minutes. Uncorrected visual acuity was 20/25 in each eye. Ocular motility was normal and the only strabismus noted was a small exophoria with near fixation. What do you think could be going on?