Homonymous Quadrantanopsia

Definition

Homonymous quadrantanopsia is defined as the visual loss that is restricted to one quadrant of the visual field and is comparable in both eyes. Thus, when looking straight ahead, patients may have difficulty seeing objects or movement in the upper or lower quadrant of the visual field, but it will be in the same quadrant (i.e., either to the right or to the left) regardless of which eye is being tested. Depending on the extent of the lesion, slightly more or slightly less than one quarter of the visual field may actually be affected. Homonymous quadrantanopsia usually results from lesions posterior to the lateral geniculate nuclei, which encroach either on the optic radiations or the primary visual cortex. The visual fibers from the upper portion of the retina retain their relative superior position as they travel back to the visual cortex. The opposite is true of the fibers derived from the lower portion of the retina. Consequently, damage restricted to the more dorsal...