Hemianopsia
Hemianopsia, is less vision or blindness in half the visual field, usually on one side of the vertical midline.
It is most commonly caused by damage from stroke, brain tumor, or trauma.
Temporary hemianopsia can occur as part of the aura phase of migraine.
When hemianopsia pathology involves both eyes, it is either homonymous or heteronymous.
A homonymous hemianopsia is the loss of half of the visual field on the same side in both eyes.
The visual images that we see to the right side travel from both eyes to the left side of the brain, while the visual images we see to the left side in each eye travel to the right side of the brain.
Damage to the right side of the posterior portion of the brain or right optic tract can cause a loss of the left field of view in both eyes.
Damage to the left posterior brain or left optic radiation can cause a loss of the right field of vision.
Heteronymous hemianopsia is the loss of half of the visual field on different sides in both eyes.
Binasal hemianopsia refers to the loss of the fields surrounding the nose.
Bitemporal hemianopsia is the loss of the fields closest to the temples.
In Superior hemianopsia the upper half of the field of vision is affected.
In Inferior hemianopsia the lower half of the field of vision is affected.
Quadrantanopia is decreased vision or blindness in one quarter of the visual field.
The quarter of vision missing is dependent on the location of the brain damage, if the lesion is temporal or parietal, and the site of the side of the lesion.