visual pathway:optic tract, lateral geniculate body (LGB), optic radiations, and visual cortex.

👁 Visual Field Defects by Lesion Location (Part 2)

Following the previous overview of optic chiasm lesions,
this summary focuses on the next segments of the visual pathway:
optic tract, lateral geniculate body (LGB), optic radiations, and visual cortex.

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🧠 Key Visual Terminology

TermMeaning

Homonymous	Same-side (matching) field loss
Congruous	Symmetrical, identical field loss
Incongruous	Asymmetrical field loss
Hemianopia	Half-field loss
Quadrantanopia	Quarter-field loss
Sectoranopia	Sector-shaped field loss

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🧬 Lesion-Specific Field Defects

1. Optic Tract

• Incongruous contralateral homonymous hemianopsia
• RAPD (+), Bowtie atrophy may occur

2. Lateral Geniculate Body (LGB)

• Congruous contralateral sectoranopia
• Lateral lesion → superior field loss
• Medial lesion → inferior field loss

3. Optic Radiations

LobeField DefectDetail

Temporal	Pie in the Sky	Meyer's loop → superior field
Parietal	Pie in the Floor	Baum's loop → inferior field

4. Visual Cortex

Area AffectedDefect Type

Posterior tip (one side)	Macular-involving hemianopsia
Anterior tip (one side)	Half-moon scotoma
Bilateral posterior tips	Macular bilateral scotomas
Bilateral superior areas	Inferior bilateral field loss
Diagonal involvement	Checkboard field pattern

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✅ Summary

• More posterior lesions → more congruous field loss
• Temporal lobe → upper field defect, Parietal lobe → lower field defect
• Visual field testing is critical for localizing cortical and retrochiasmal lesions