๐ Brain & Eye Connection: Visual Field Clues to Brain Lesions
The eye is embryologically part of the brain, and many central nervous system lesions produce visual field defects.
Hence, neuro-ophthalmic signs can point toward intracranial pathology.
๐ Visual Pathway Overview
- Retina
- Optic nerve
- Optic chiasm
- Optic tract
- Lateral geniculate body (LGB)
- Optic radiation
- Meyer's loop (temporal lobe): upper visual field
- Baum's loop (parietal lobe): lower visual field
- Visual cortex
๐ฏ Visual Field Rule of Thumb
Lesion LocationField Defect
| Right brain | Left field defect |
| Left brain | Right field defect |
| Superior lesion | Inferior field loss |
| Inferior lesion | Superior field loss |
๐ง Optic Chiasm Lesion Patterns
Lesion SiteVisual Field DefectNotes
| Anterior chiasm | Junctional scotoma | Ipsilateral central + contralateral superotemporal |
| Middle chiasm (inferior) | Bitemporal hemianopsia from top down | Often pituitary adenoma |
| Middle chiasm (superior) | Bitemporal hemianopsia from bottom up | Often suprasellar tumor |
| Posterior chiasm | Central bitemporal hemianopic scotoma | Rare |
โ Summary
- Visual field testing is a critical noninvasive diagnostic clue
- Chiasmal lesions cause bitemporal hemianopsia
- Understanding visual pathway anatomy aids in neuroimaging interpretation and localization
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