Abstract

A patient with multiple sclerosis and bilateral retrochiasmal visual field defects is reported. Homonymous field defects are rare in multiple sclerosis despite the frequency of pathological involvement of the retrochiasmal visual pathways. A higher incidence might be found with a higher index of suspicion and careful visual field testing with qualitative confrontation technique. Other reasons for the infrequent clinical detection of retrochiasmal lesions are considered. Such lesions may exist without demonstrable defect. This may be explained by anatomical factors, for example, fibre arrangement, or physiological factors, such as, geniculate or retrogeniculate integration. Lesions producing demonstrable defects may be asymptomatic because they: affect only the peripheral field, are small scotomas that do not impair visual acuity, affect only one eye, or occur late in the course of disease when masked by optic nerve involvement.