Homonymous hemianopsia

Homonymous hemianopsia is a medical term for a type of partial blindness resulting in a loss of vision in the same visual field of both eyes.

Causes
It is usually caused by injury to the brain itself such as stroke or trauma, rather than malfunctioning of the eye itself.

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.

Etymology
Homonymous hemianopsia can be broken down as follows:

Homonymous hemianopsia is also called Homonymous hemianopia.
 * Homonymous: same
 * hemi: half of the visual field
 * anopsia: blindness