Vascular and neoplastic (malignant or benign tumours) lesions of the optic tract, visual cortex or uncal herniation can cause a contralateral homonymous hemianopsia. For example, a person who has a lesion of the right optic tract will no longer see objects on their left side. Similarly, a person who has a stroke to the right occipital lobe will have the same visual field defect, but there will be macular sparing.
A stroke on the entire right side of the brain, in addition to producing a homonymous hemianopsia, will also lead to the syndrome of Hemispatial neglect.
However, the symptom of homonymous hemianopsia isn't necessarily of a lethal cause. For instance, it can constitute the aura phase of migraine.
Homonymous hemianopsia is also called Homonymous hemianopia.