What is incongruous homonymous hemianopia?
What is incongruous homonymous hemianopia?
A congruous visual field defect is identical between the two eyes, whereas an incongruous defect differs in appearance between the eyes. For lesions behind the LGN, visual field defects are generally more congruous if the lesion is located more posteriorly along the visual pathway.
What causes optic tract lesions?
Optic tract lesions are most commonly caused by infarction (40%), tumors (32%), and trauma (17%) (Zhang et al., 2006b). Rarely, demyelinating disease may involve the optic tract in isolation (Savino et al., 1978; Rosenblatt et al., 1987).
Why does MCA stroke affect vision?
Nerves from each eye travel together in the brain, so both eyes are affected. If the right side of your brain is damaged, the left side vision in each eye may be affected. It is rare for both sides of the brain to be affected by stroke. When it does happen, it can result in blindness.
What type of stroke causes homonymous hemianopia?
3 Homonymous hemianopia is a loss of the right or left halves of the visual field of both eyes (Figure 1a, 1b) and usually occurs as a result of a middle cerebral or posterior cerebral artery stroke affecting either the optic radiation or visual cortex of the occipital lobe (Figure 2).
What kind of brain damage would result in hemianopia?
However, any disorder that affects the brain — including tumors, inflammation and injuries — can be a cause. It is estimated that 70% of the injuries leading to hemianopsias are due to an obstruction (blockage) of the blood supply (stroke). Fifteen percent are due to tumors, and 5% are due to bleeding in the brain.
Why is macular sparing?
Causes. The favored explanation for why the center visual field is preserved after large hemispheric lesions is that the macular regions of the cortex have a double vascular supply from the middle cerebral artery (MCA) and the posterior cerebral artery (PCA).
What happens if there is a lesion at the optic tract?
A lesion in the left optic tract will cause right-sided homonymous hemianopsia, while a lesion in the right optic tract will cause left-sided homonymous hemianopsia. Stroke, congenital defects, tumors, infection, and surgery are all possible causes of optic tract damage.
What effect would a lesion in the left optic tract have on vision?
Optic nerve lesions The optic nerve, also known as cranial nerve II, extends from the optic disc to the optic chiasma. Lesions in optic nerve causes visual field defects and blindness.
What type of stroke causes vision loss?
Retinal vessel occlusion Occasionally, a loss of central vision is due to a type of stroke affecting the retina, the light- sensitive area of nerves at the back of the eye. This is called a retinal vessel occlusion. It happens when there is a blockage in one of the blood vessels to your eye.
Can vision return after eye stroke?
You may regain your vision after an eye stroke. Most people are left with some vision loss. Some cases can lead to blindness.
Which lesion causes homonymous hemianopia?
Any type of intracranial lesion in the appropriate location can cause a homonymous hemianopia; however, vascular causes (cerebral infarction and intracranial hemorrhage) are the most frequent in adults, ranging from 42 to 89 percent, followed by brain tumors, trauma, surgical interventions, and other central nervous …
Where is lesion for homonymous hemianopia?
When homonymous hemianopia exists the lesion is definitely lateralized on the opposite side, but it may be located at any site along the visual pathway between and including the visual center in the occipital lobe and the chiasm.
