Visual Field Defects

Question 1

What is a ‘scotoma’?

Answer 1

A localised defect in the retina resulting in a noticeable blind spot in the normal visual field.
Note: the anatomical blind spot is found at the optic disc, as no photoreceptors are found here.

Question 2

What condition does damage to the optic nerve coming from one eye result in?

Answer 2

Ipsilateral monocular blindness.

Question 3

What can’t you see if you have bitemporal hemianopia and where is the lesion that results in this condition?

Answer 3

Loss of peripheral vision. Lesion of the optic chias means that you lose nasal inputs to vision = temporal visual fields lost.

Question 4

What lesions can lead to contralateral homonymous hemianopia?

Answer 4

Damage to Medial chiasm
Damage to the optic tract
Damage to the lateral geniculate nucleus
Damage to both optic radiations

Question 5

Give an example of damage that results in contralateral homonymous hemianopia with macular sparing and explain why this occurs.

Answer 5

Occlusion of the posterior cerebral artery.
Dual blood supply to the macula, means that even with damage to the PCA, it still receives blood supply from the deep branch of the middle cerebral artery. Therefore this part of the visual field is unaffected.

Question 6

What lesion leads to a “pie in the sky” visual field defect?

Answer 6

Damage to the inferior optic radiations in the temporal lobe (Meyer’s loop) leads to a loss of one half of the superior visual field known as a ‘contralateral homonymous superior qudrantanopia’.

Question 7

What does ‘homonymous’ mean?

Answer 7

Affects both eyes in the same way e.g. will affect the same side of each eye.

Question 8

Damage to the superior optic radiation results in what visual field defect?

Answer 8

Contralateral homonymous inferior quadrantanopia.