Visual Field Defects Quiz: Localize the Lesion
Updated
Visual field defects localize the lesion: optic nerve causes monocular blindness, chiasm causes bitemporal hemianopia, tract and beyond cause contralateral homonymous defects. Temporal lobe (Meyer's loop) affects superior quadrant, parietal affects inferior quadrant, occipital may spare the macula.
This quiz tests your ability to localize lesions along the visual pathway based on the resulting visual field defect. It is designed for medical students, neurology residents, and anyone reviewing neuroanatomy. Each question presents a field defect and asks you to identify the most likely site of damage, from the optic nerve to the occipital cortex.
Understanding the anatomy is key: fibers from the nasal retina cross at the optic chiasm, while temporal fibers remain ipsilateral. Consequently, lesions at or before the chiasm produce different patterns than those after it. Post-chiasmal lesions yield contralateral homonymous defects, with specific patterns indicating the location along the optic radiations or cortex.
The questions
A patient reports complete loss of vision in the right eye. Where is the most likely lesion?
A pituitary adenoma compresses the optic chiasm. Which visual field defect is expected?
At the optic chiasm, which retinal ganglion cell axons decussate to the contralateral side?
A lesion in the left optic tract produces which visual field defect?
You examine a patient with a left homonymous hemianopia that is incongruous (the defect differs in each eye). Where is the lesion most likely located?
A lesion in Meyer's loop of the temporal lobe causes which visual field defect?
A lesion in the parietal lobe optic radiations causes which visual field defect?
A patient has a right homonymous hemianopia with macular sparing. Where is the lesion?
Why does macular sparing often occur with occipital cortex lesions?
Bilateral destruction of the occipital lobes causes which condition?
A patient presents with a central scotoma in the left eye only. Where is the most likely lesion?
A lesion in the optic radiations of the parietal lobe most often damages fibers from which part of the retina?
Which statement best distinguishes optic tract lesions from occipital cortex lesions?
A lesion in the anterior optic radiation (Meyer's loop) is most often caused by pathology in which lobe?
A stroke in which artery most commonly causes an isolated homonymous hemianopia with macular sparing?
0 of 15 answered · 0 correct
Cheat sheet: key terms
| Optic nerve | Lesion causes ipsilateral monocular blindness (complete loss of vision in that eye). |
|---|---|
| Optic chiasm | Lesion causes bitemporal hemianopia (loss of temporal fields in both eyes). |
| Optic tract | Lesion causes contralateral homonymous hemianopia (loss of half of visual field opposite the lesion). |
| Meyer's loop | Temporal lobe fibers; lesion causes contralateral superior quadrantanopia ("pie in the sky"). |
| Parietal radiations | Parietal lobe fibers; lesion causes contralateral inferior quadrantanopia ("pie on the floor"). |
| Occipital cortex | Lesion causes contralateral homonymous hemianopia, often with macular sparing if the posterior pole is spared. |
| Macular sparing | Preservation of central vision in occipital lesions, often attributed to dual blood supply or bilateral representation. |
| Congruity | Post-chiasmal lesions are typically congruous, but optic tract lesions are often incongruous. |
Answers explained
Show all 15 answers
- A patient reports complete loss of vision in the right eye. Where is the most likely lesion? Right optic nerve. The optic nerve carries all visual information from one eye, so a complete monocular blindness localizes to the ipsilateral optic nerve.
- A pituitary adenoma compresses the optic chiasm. Which visual field defect is expected? Bitemporal hemianopia. Compression of the chiasm damages crossing nasal fibers from both eyes, causing loss of both temporal visual fields.
- At the optic chiasm, which retinal ganglion cell axons decussate to the contralateral side? Nasal retinal fibers. Fibers from the nasal retina cross at the chiasm, while temporal fibers remain ipsilateral; this arrangement underlies binocular vision.
- A lesion in the left optic tract produces which visual field defect? Right homonymous hemianopia. The left optic tract contains fibers from the right half of both retinas, so damage causes loss of the right visual field in both eyes (contralateral homonymous hemianopia).
- You examine a patient with a left homonymous hemianopia that is incongruous (the defect differs in each eye). Where is the lesion most likely located? Right optic tract. Optic tract lesions produce incongruous defects because fibers from corresponding retinal points are not yet perfectly aligned; cortical lesions are congruous.
- A lesion in Meyer's loop of the temporal lobe causes which visual field defect? Contralateral superior quadrantanopia. Meyer's loop carries fibers from the inferior retina (superior visual field) for the contralateral side, so damage causes a 'pie in the sky' defect.
- A lesion in the parietal lobe optic radiations causes which visual field defect? Contralateral inferior quadrantanopia. Parietal radiations carry fibers from the superior retina (inferior visual field), so damage causes a 'pie on the floor' defect.
- A patient has a right homonymous hemianopia with macular sparing. Where is the lesion? Left occipital cortex. Macular sparing is typical of occipital cortex lesions because the macula has dual blood supply and is represented over a large cortical area.
- Why does macular sparing often occur with occipital cortex lesions? The macula has dual blood supply from middle and posterior cerebral arteries. The macular region receives blood from both the middle and posterior cerebral arteries, so it can survive ischemia affecting only one territory.
- Bilateral destruction of the occipital lobes causes which condition? Cortical blindness. Complete loss of visual cortex bilaterally results in cortical blindness; Anton syndrome is a rare denial that may accompany but is not the primary defect.
- A patient presents with a central scotoma in the left eye only. Where is the most likely lesion? Left optic nerve. A central scotoma confined to one eye indicates damage to the optic nerve or macula on that side, as chiasmal and post-chiasmal lesions affect both eyes.
- A lesion in the optic radiations of the parietal lobe most often damages fibers from which part of the retina? Superior retina (inferior visual field). Parietal radiations (the superior fibers) carry axons from superior retinal quadrants, which see the inferior visual field.
- Which statement best distinguishes optic tract lesions from occipital cortex lesions? Tract lesions produce incongruous defects; cortex lesions produce congruous defects. Optic tract fibers are not yet topographically aligned, so defects are incongruous; by the time fibers reach the cortex, the representation is precise, yielding congruous defects.
- A lesion in the anterior optic radiation (Meyer's loop) is most often caused by pathology in which lobe? Temporal lobe. Meyer's loop sweeps anteriorly into the temporal lobe before turning posteriorly, so temporal lobe lesions (e.g., tumors, strokes) commonly affect it.
- A stroke in which artery most commonly causes an isolated homonymous hemianopia with macular sparing? Posterior cerebral artery. The posterior cerebral artery supplies the occipital cortex; occlusion causes hemianopia, often with macular sparing due to collateral supply from the middle cerebral artery.
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