Visual field defects

Question 1

What happens at the optic chiasm?

Answer 1

Fibres from the nasal half of the retina, corresponding to the temporal visual field, decussate

This decussation is a key feature of visual pathway organization.

Question 2

What is the result of lesions compressing the optic chiasm? What causes these lesions?

Answer 2

Bitemporal hemianopia

Such lesions are often caused by pituitary adenomas.

Question 3

What is homonymous contralateral quadrantanopia caused by?

Answer 3

Lesions to optic radiations

These lesions include MCA stroke.

Question 4

What causes ipsilateral monocular blindness? Which conditions are included?

Answer 4

Optic nerve lesions
#optic neuritis
#optic atrophy
#trauma

Question 5

What type of hemianopia is caused by central optic chiasm lesions? What causes these?

Answer 5

Bitemporal hemianopia

These lesions can be due to pituitary adenoma or suprasellar aneurysm.

Question 6

What occurs with lateral optic chiasm lesions?

Answer 6

Ipsilateral nasal hemianopia

Conditions such as internal carotid and posterior communicating artery atheromas can cause this.

Question 7

What is the result of optic tract lesions?

Answer 7

Contralateral homonymous hemianopia

These lesions can arise from MCA stroke and tumours.

Question 8

What happens when there are lesions in the occipital cortex?

Answer 8

Contralateral homonymous hemianopia with macular sparing

Such lesions can be due to PCA stroke and trauma.