Neuro-ophthalmology
Visual field defects in neuro-ophthalmology
Where a lesion sits along the visual pathway decides the shape of the field defect. Select a site on the pathway to see the field of each eye, and why it looks that way.
Seen from above: the patient’s right is on your right. Each fibre is coloured by the half of the visual field it carries.
Site 1
Left optic nerve
Fields are drawn as the patient sees them. Black marks the lost field.
No light perception in the left eye
Every fibre from the left eye runs in the left optic nerve, before any of them cross. A complete lesion leaves the left eye blind while the right eye’s field stays normal. Expect a relative afferent pupillary defect on the left. Partial lesions give central scotomas or altitudinal defects in that eye alone.
Reading the pattern
- In front of the chiasm, a lesion affects one eye only.
- At the chiasm, the crossing nasal fibres are hit, so the defect is bitemporal.
- Behind the chiasm, the defect is homonymous: the same half of the field in both eyes, on the side opposite the lesion.
- The further back the lesion, the more alike the two fields: tract lesions are incongruous, occipital lesions almost identical.
- Temporal lobe lesions take the upper quadrant and parietal lesions the lower one. Occipital lesions often spare the macula.
The nine sites at a glance
| Site | Left eye · right eye | Field defect |
|---|---|---|
| No light perception in the left eye | ||
| Bitemporal hemianopia | ||
| Incongruous left homonymous hemianopia | ||
| Right homonymous sectoranopia | ||
| Right homonymous upper quadrant defect (“pie in the sky”) | ||
| Right homonymous defect, denser below | ||
| Right homonymous lower quadrantanopia, macula spared | ||
| Right homonymous upper quadrantanopia, macula spared | ||
| Left homonymous hemianopia, macula spared |
A teaching schematic, not to scale. Real lesions are rarely this clean: interpret every field with the clinical picture and imaging.