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(FRAME-INFO (STRING "Visual Field Defects. This diagram is a schematic summary of the visual field defects caused by lesions \(hatched contours\) at different points in the visual system.  At right, the visual field is shown separately for each eye for each lesion. 1: A lesion through the right optic nerve produces blindness in the right eye. 2: A lesion through the optic chiasm produces loss of the temporal fields in both eyes \(bitemporal hemianopia\). 3: Lesioning the uncrossed fibers coming from right eye produces loss of the nasal field of the right eye \(right nasal hemianopia\).  4:  A lesion through the right optic tract produces loss of the left visual field, that is the temporal field of the left eye and the nasal field of the right eye \(left homonymous hemianopia\).  5: A lesion through the right optic radiations that pass directly back to the occipital lobe produces loss of the inferior quadrant of the left visual field \(left lower quadrantanopia\).  6: A lesion through right optic radiations in Meyer's loop produces loss of the superior quadrant of the left visual field \(left upper quadrantanopia\).  7: A lesion through all the right optic radiations produces loss of the left visual field \(left homonymous hemianopia\).  8: A lesion involving the right visual cortex on the medial surface of the brain produces loss of the left visual field but with macular sparing \(left homonymous hemianopia with macular sparing\), because the macular \(foveal\) representation extends beyond the medial surface and onto the posterolateral surface of the hemisphere."))