Is one eye better than two in strabismus? Or does the misaligned amblyopic eye interfere with binocular vision? A preliminary functional MRI study.

Purpose: The aim of this study was to determine if patients with strabismic amblyopia could have increased occipital visual cortex activation with monocular stimulation of the sound fixing eye, rather than with simultaneous stimulation of both eyes.

Methods: A prospective study was performed including 12 patients with strabismus and amblyopia, who were evaluated using functional MRI with visual stimulation paradigms. The measurements were made in the occipital visual cortex, assessing the response to the binocular and monocular stimulation.

Results: 12 out of 12 patients showed an increased cortical response of the healthy eye in comparison to the amblyopic one. Nine of the 12 patients showed larger cortical activation with visual stimulation of the healthy eye compared to the binocular condition analysis. Three out of the 12 cases had a greater activation area when the stimulation was binocular rather than monocular, 2 of whom had a relatively small angle of strabismus.

Conclusions: Patients with amblyopia and strabismus could see better with only one eye instead of both eyes. This could be related to inhibition of the binocular function of the brain by the misaligned amblyopic eye.