Background: Cyclic esotropia is a rare form of strabismus characterized by regularly alternating periods of ET with straight eyes and normal binocular vision.
Case Report: A 13-year-old (AP) presented with ET and intermittent horizontal diplopia of 1.5 years duration that was worse in the morning and improved as the day progressed. Medical and ocular histories were unremarkable.
Visual acuity with habitual correction of -4.75 DS OD was 20/20 and -5.00-0.25 x 045 OS was 20/15. Cycloplegic refraction was -5.50 DS OD and -6.00 DS OS. AP had a comitant constant right ET of 35ż at 3m and 40ż at 40cm. Worth dot testing revealed uncrossed diplopia at 3m and 40cm, which was eliminated with 45żBO and 40żBO, respectively. Major amblyoscope testing revealed normal correspondence.
At our request, AP kept a 1-month diary that confirmed our suspicion of the presence of cyclic ET with a 24-hour pattern (12 hours of ET followed by 12 hours of straight eyes). Initially, AP underwent 10 vision therapy sessions to maximize his divergence ability. Although this resulted in much better control of the ET, it was extremely difficult for AP to align his eyes in the morning and he was not always successful. Thus, we recommended strabismus surgery to decrease the angle of strabismus. After undergoing strabismus surgery, alignment was 6ż esophoria and 18ż esophoria at 6m and 40cm, respectively. Diplopia no longer occurred and asthenopia was not an issue. Eye alignment remained stable 1-year post surgery.
Conclusion: This case demonstrates the successful outcome of vision therapy treatment performed prior to strabismus surgery in a patient with cyclic ET.