The role of binocular occlusion in determining the preferred eye for fixation in intermittent exotropia: a guide to choosing the eye for unilateral surgery.

Introduction And Purpose: This study aims to determine whether a binocular occlusion test for distance in intermittent exotropia could reliably show the most frequently deviating eye. With the reliable demonstration of such an event this test can be very helpful in selecting the appropriate eye for surgery when a unilateral lateral rectus recession is planned for the treatment of an intermittent exotropia.

Patients And Method: 24 patients (11 males, 13 females) aged 2.4 to 21 years (mean 5.7, SD ± 4) with intermittent exotropia were recruited. Subjects were excluded if they had had previous strabismus surgery, uncorrectable poor vision in one or both eyes, neurological disorders, other ocular motility disorders (e.g., Duane syndrome, Brown syndrome), or inability to cooperate during the test. The dominant eye was first determined using the sighting test and the near point of convergence test. The binocular cover test, while fixating a distant target, was then performed and ocular divergence was noted.

Results: The binocular occluder test consistently demonstrated the diverging eye to be the non-dominant eye.

Conclusion: The bilateral occlusion test for distance in intermittent exotropia can reliably show the most frequently deviating eye. Clinicians may find this test helpful in selecting the eye for surgery in patients where unilateral lateral rectus recession for the treatment of an intermittent exotropia is being considered.