Why does a stroke in the left occipital lobe blind the right half of both eyes? · Grey Matter

After the chiasm, the left visual pathway carries the right half of the visual field from both eyes, so destroying the left visual cortex removes that half from each eye's view: a right homonymous hemianopia.

Why does a stroke in the left occipital lobe blind the right half of both eyes?

After the chiasm, the left visual pathway carries the right half of the visual field from both eyes, so destroying the left visual cortex removes that half from each eye's view: a right homonymous hemianopia. Covering one eye does not change the defect, which is how it is told apart from damage to an eye or an optic nerve. With an occipital stroke the central few degrees are often spared, because the occipital pole where central vision is mapped often also receives blood from the middle cerebral artery.