A homonymous hemianopia that respects the vertical meridian with preservation of central vision is most characteristic of a lesion in which location?

Explanation

## Anatomical Basis of Homonymous Hemianopia **Key Point:** Homonymous hemianopia with macular sparing (central vision preserved) is the hallmark of occipital cortex (primary visual cortex/striate cortex) lesions. ### Why Macular Sparing Occurs The macula has dual blood supply: - Middle cerebral artery (MCA) — supplies the occipital pole - Posterior cerebral artery (PCA) — supplies the medial occipital cortex When a single vascular territory is affected (e.g., MCA or PCA stroke), the macula escapes because collateral circulation from the other artery preserves central vision. ### Visual Field Defect Pattern | Location | Field Defect | Macular Sparing | Characteristics | |----------|--------------|-----------------|------------------| | **Optic tract** | Homonymous hemianopia | NO | Incongruous; pupillary defect present | | **Lateral geniculate nucleus** | Homonymous hemianopia | NO | Incongruous; "sectoranopia" pattern | | **Primary visual cortex** | Homonymous hemianopia | YES | Congruous; respects vertical meridian | | **Optic chiasm** | Bitemporal hemianopia | N/A | Central scotoma may occur | **High-Yield:** Macular sparing + homonymous hemianopia = **occipital cortex lesion** (usually vascular). ### Congruity in Cortical Lesions Lesions of the striate cortex produce **congruous** visual field defects (both eyes have identical field loss in shape and size) because the visual pathways are tightly organized at the cortical level. **Clinical Pearl:** A patient with acute homonymous hemianopia and macular sparing should raise suspicion for posterior cerebral artery (PCA) or middle cerebral artery (MCA) stroke affecting the occipital lobe.