The Challenge of Strabismus Surgery for Patients with Hemianopic Visual Field Defects Associated with Ocular Deviations.

Homonymous and heteronymous hemianopias associated with strabismus are a therapeutic challenge because surgery may result in diplopia, decrease the visual field (VF), and/or lead to recurrence of the deviation. We present four cases: two homonymous hemianopias and two heteronymous hemianopias. Of the four patients, three had exotropia and one had esotropia. The origin of hemianopias was neoplastic in two cases and traumatic in two cases. Strabismus surgery was performed in three cases, but only one case had a good result; recurrence of the deviation and diplopia occurred in the other two cases. In conclusion, exotropia may develop as a compensatory mechanism in a patient with congenital or early-onset homonymous hemianopia and realigning the eyes could reduce the binocular VF and cause diplopia. In heteronymous hemianopias, there is little risk of the surgery causing diplopia, but the strabismus is unstable because of the absence of binocular vision and vergence reflexes if VF loss includes the macula. Further, strabismus, in association with hemianopia, may be caused by coexistent cranial nerve and/or gaze palsy. The prognosis, objective, and results of the strabismus operation should be clearly discussed with the patients or their guardians before it is performed if hemianopias are present.