Localising a visual field defect
- Clinical approach
The shape of a field defect shows the lesion: one eye is the eye or optic nerve, both temples the chiasm, the same side in both eyes the brain behind.
See it in 3D: Optic nerve · Optic chiasm · Geniculate bodies · Visual cortex
What it is
Each part of the visual pathway produces a typical field defect. In front of the chiasm, defects affect one eye: a central scotoma in optic neuritis, an altitudinal defect in ischaemic optic neuropathy, an arcuate defect in glaucoma. At the chiasm the crossing nasal fibres are hit, giving a bitemporal hemianopia. Behind the chiasm, the defect is homonymous (the same side in both eyes) and on the side opposite the lesion; the more posterior, the more alike the defects in the two eyes.
Red flags
- New homonymous hemianopia of sudden onset: stroke, a stroke code.
- Bitemporal defect with sudden headache, vomiting or eye-movement palsy: pituitary apoplexy.
- Bitemporal defect with gradual onset: pituitary adenoma, craniopharyngioma (children) or meningioma.
- Field defect with papilloedema.
- A patient who drives or operates machinery.
Step-by-step approach
- Test each eye separately by confrontation, then formally with automated perimetry.
- Decide whether the defect is in one eye or both.
- If both: does it respect the vertical midline, and is it on both temporal sides (chiasm) or on the same side (behind the chiasm)?
- Judge congruity: very similar defects in the two eyes point to the occipital lobe.
- Correlate with the rest of the neurological exam and image the suspected level.
Field defects and where the lesion is
| Defect | Site | Typical cause |
|---|---|---|
| Loss in one eye, central scotoma | Optic nerve | Optic neuritis, toxic optic neuropathy |
| Upper or lower half of one eye (altitudinal) | Optic nerve head or retina | Ischaemic optic neuropathy, branch artery occlusion |
| Arcuate defect | Optic nerve head | Glaucoma |
| Bitemporal hemianopia | Chiasm | Pituitary adenoma |
| Homonymous hemianopia, incongruous | Optic tract | Tumour, demyelination |
| Superior homonymous quadrantanopia | Temporal lobe (Meyer loop) | Stroke, tumour |
| Inferior homonymous quadrantanopia | Parietal lobe | Stroke, tumour |
| Congruous homonymous hemianopia, macula spared | Occipital cortex | Posterior cerebral artery stroke |
Keys to the differential
- Macular sparing in occipital stroke happens because the macular cortex has a dual blood supply from the middle and posterior cerebral arteries.
- Pituitary adenomas compress the chiasm from below, so the superior temporal quadrants are usually lost first.
- Patients with homonymous hemianopia often complain of trouble reading or bumping into things on one side, not of loss in one eye.
Next step / Initial management
- Sudden homonymous loss: emergency stroke pathway with brain imaging.
- Bitemporal loss: MRI of the pituitary region and a pituitary hormone panel (prolactin, IGF-1, morning cortisol, thyroid tests); refer to neurosurgery and endocrinology.
- Suspected pituitary apoplexy: emergency imaging, corticosteroid replacement and neurosurgery.
- Document the defect with automated perimetry for follow-up, and advise on driving according to the national rules.
Test yourself
Think of the answer, then tap the question to see it.
Where is the lesion in a bitemporal hemianopia?
At the optic chiasm, where the crossing nasal fibres from both eyes are compressed, most often by a pituitary adenoma.
Which field defect does a temporal lobe lesion cause?
A contralateral superior homonymous quadrantanopia, from damage to Meyer's loop.
Why is the macula often spared in occipital stroke?
Because the occipital pole has a dual blood supply from the posterior and middle cerebral arteries.
Elsewhere in DurgiPedia
- The visual pathway, pupillary reflexes and eye movements
- Eye exam: visual acuity, visual fields and eye movements
Connections
See it in 3D4
The structures of Durgical's 3D anatomy where it is found.
Educational content; not a clinical guideline and no substitute for assessment by a health professional. For sudden visual loss, severe eye pain, a chemical burn or an eye injury, go to an emergency department at once.
Sources: Neuroanatomy, Visual Pathway (StatPearls Publishing (NCBI Bookshelf), 2026); Neuroanatomy, Optic Chiasm (StatPearls Publishing (NCBI Bookshelf), 2023); Humphrey Visual Field (StatPearls Publishing (NCBI Bookshelf), 2025).
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Representative model, for educational purposes only.