He was wearing OD: -5.50-1.75x67 and OS: -5.00-1.75x95. Visual acuity was 20/20 OD and 20/25 OS that corrects to 20/20 with pinhole. Dilated fundus examination was unremarkable with no ischemic signs. Colour vision was 17/17 Ishihara plates. Pupils reacted from 4 to 3mm with light bilaterally. There was no relative afferent defect noted. Stereopsis was normal at 40 seconds of arc. Retinal artery pressures are 50/15 on the right and 55/12 on the left. Lids were symmetrical. Slit lamp examination and intraocular pressure readings were normal.
Orthoptics testing noted an underaction of the both lateral rectus muscles of -1 in the left and -0.5 in the right. Examination with Hess confirmed the bilateral lateral rectus palsy. In primary position, the esotropia was 10 prism diopter (PD) and the hypotropia was 2 PD at distance with his corrective lenses. At near, the esotropia was only minimal at 1 PD without any hypotropia. On sustained right gaze, the tiny esotropia broke into an exotropia of 35-40 PD (Video). The deviations did not change in any other sustained directions of gaze. After he broke into the exotropia, he had trouble recovering control and the exotropia persisted in all gaze positions for approximately one minute. The same esotropia transforming to a large exotropia was observed in left gaze.
Cranial nerve V and VII was normal as tested by facial sensation and lid closure strength respectively. However, left hearing was decreased compared to the right. The rest of his physical examination was unremarkable.
Video (requires Windows Media Player to view)
The eye movements show esotropia in all positions. However, after eccentric gazes he developed a large angle of exotropia which gradually returned to his resting state of alignment.