Patients with strabismus who strongly favor one eye for fixation and who have a unilateral rather than an alternating fixation pattern are most likely to acquire strabismic amblyopia.

Before discussing the surgical management of congenital exotropia, treatment of amblyopia must be the first target of the physician in such cases. In occlusion therapy the fixating eye is prevented from taking part in the act of vision so that the patient is forced to use the amblyopic eye. In addition, occlusion removes the inhibitory stimuli to the amblyopic eye that arise from stimulation of the fixating eye.

As a rule, the fixating eye should be occluded completely and constantly during all waking hours. Occlusion of the sound eye for an hour or so a day as practiced by some is rarely beneficial. In an effort to prevent occlusion amblyopia, we alternate occlusion of the sound eye with occlusion of the amblyopic eye. During the first year of life the sound eye is patched for 3 days, followed by patching of the amblyopic eye for 1 day (3:1 rhythm). During the second year of life, the occlusion period of the sound eye can be extended to 4 days, followed by 1 day of occlusion of the amblyopic eye. In 3- to 4-year-old children, the occlusion period of the fixating eye can be further lengthened, provided the physician monitors visual acuity of both eyes at frequent intervals. The same principle applies in younger children. If 3:1 or 4:1 occlusion fails to bring about improvement, the period of occlusion of the sound eye may be lengthened and visual acuity, fixation preference, or both are checked at intervals not to exceed 4 weeks. Once the vision of the amblyopic eye has been improved to the level of the fixating eye, the patient must be followed closely. Amblyopia tends to recur until children have reached 8 to 10 years of age or even older because of the persistence of inhibitory effects from the fixating eye.