Figure 24: Typical Visual Field Defects Associated with Discrete Lesions Along the Visual Pathways

Specific monocular or binocular visual field defects can be highly localizing when the neuroanatomy of the visual pathways is understood. The temporal visual field corresponds to the nasal retina, while the nasal visual field corresponds to the temporal retina. 1) Left optic nerve lesion - while an optic neuropathy can cause a variety of monocular visual field defects (see Figure ***), a complete lesion will cause no light perception vision loss in the affected eye (the violet color = a combination of damage to both nasal and temporal fibers). 2) Lesion at the junction of proximal left optic nerve and chiasm - a junctional lesion, when complete, can cause complete monocular vision loss OS due to optic neuropathy, but because some fibers originating in the right inferonasal retina decussate in the chiasm and then bulge forward into the left anterior chiasm/proximal nerve (anatomically known as ‘Wilbrand's knee', a somewhat controversial concept), a small superotemporal (‘junctional') scotoma can be seen in the right eye. 3) Chiasmal lesion - due to involvement of the crossing fibers (responsible for temporal visual fields) coming from right and left eyes, bitemporal hemianopia is the result. 4) Left optic tract lesion - since this is a retro-chiasmal lesion, a right homonymous hemianopia (HH, and usually a mild right relative afferent pupillary defect) is the result. When incomplete, these tend to be incongruous (asymmetric). When complete, the HH is non-localizing (e.g., could be tract or could be occipital). 5) Left lateral geniculate nucleus lesion - there are two characteristic visual field patterns: a. right homonymous quadruple sectoranopia, b. right homonymous horizontal sectoranopia. 6) Left temporal lobe (Meyer's loop) - right superior quadrantic defect ("pie in the sky"), that when incomplete, may be incongruous. 7) Left parietal lobe - right HH that is more dense inferiorly ("pie on the floor") and often incomplete. 8) Left occipital lobe, superior to calcarine fissure - right inferior quadrantic defect, congruous (symmetric) when incomplete, often with macular sparing (i.e., sparing of the occipital pole/tip due to dual vascular circulation). 9) Left occipital lobe, inferior to calcarine fissure - right superior quadrantic defect, congruous, often with macular sparing. 10) Right complete occipital lesion with sparing of the pole - can be a complete left HH, or congruous when incomplete, macular sparing. 11) Right occipital pole lesion - left homonymous central scotoma.