Cranial Nerve Eyes

Question 1

What is the relative afferent pupillary defect called?

Answer 1

Marcus-Gunn pupil

Question 2

What happens when the afferent limb in on of the optic nerve is damaged, partially or completed?

Answer 2

• both pupils will constrict less when light is shone into the affected eye compared to the healthy eye
• pupils, therefore, appear to relatively dilate when swinging the torch from the healthy to the affected eye
• relative afferent pupillary defect

Question 3

What can relative afferent pupillary defect be caused by?

Answer 3

1. retinal damage in the affected eye, secondary to central retinal artery or vein occlusion and large retinal detachment
2. Or due to significant optic neuropathy such as optic neuritis, unilateral advanced glaucoma and compression secondary to tumour or abscess

Question 4

What is unilateral efferent defect caused by?

Answer 4

compression of the oculomotor nerve

Question 5

What happens in unilateral efferent defect?

Answer 5

loss of the efferent limb of the ipsilateral pupillary reflexes

Question 6

What does unilateral efferent defect look like?

Answer 6

ipsilateral pupil is dilated and non-responsive to light entering either eye (due to loss of ciliary sphincter function)

Question 7

What does consensual light reflex in the unaffected eye look like in unilateral efferent defect?

Answer 7

still be present as the afferent pathway (i.e. optic nerve) of the affected eye and the efferent pathway (i.e. oculomotor nerve) of the unaffected eye remain intact

Question 8

What are some of acquired cause of colour vision deficiencies?

Answer 8

1. Optic neuritis: results in a reduction of colour vision (typically red).
2. Vitamin A deficiency
3. Chronic solvent exposure

Question 9

What is visual neglect/visual inattention?

Answer 9

deficit in their awareness of one side of their visual field

Question 10

When does visual neglect happen?

Answer 10

parietal lobe injury after stroke

Question 11

What side is the lesion compared to visual neglect on?

Answer 11

side of the visual field that is affected is contralateral to the location of the parietal lesion

Question 12

What is visual neglect caused by?

Answer 12

not caused by optic nerve pathology

Question 13

What is bitemporal hemianopia?

Answer 13

loss of the temporal visual field in both eyes resulting in central tunnel vision

Question 14

What is bitemporal hemianopia caused by?

Answer 14

optic chiasm compression by a tumour (e.g. pituitary adenoma, craniopharyngioma)

Question 15

What is homongynous field defects?

Answer 15

affect the same side of the visual field in each eye

Question 16

What can cause homonymous field defects?

Answer 16

1. stroke
2. tumour
3. abscess (i.e. pathology affecting visual pathways posterior to the optic chiasm)

Question 17

How do you name visual field defects?

Answer 17

1. hemianopias if half the vision is affected

2 quadrantanopias if a quarter of the vision is affected.