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semester 5- neurology > Central Visual Pathways > Flashcards

Central Visual Pathways Flashcards

1
Q

Describe the pathway of nerves from the eye to the cortex

A

Optic nerve –> Optic chiasm –> optic tracts –> Lateral geniculate ganglion –> optic radiations –> primary visual cortex

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2
Q

What do the nasal fibres contribute to?

A

Temporal fields of vision

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3
Q

What do the temporal fibres contribute to

A

Nasal fields of vision

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4
Q

Which fibres cross in the optic chiasm?

A

Nasal fibres

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5
Q

How are visual field defects classified?

A

By which area of vision is lost

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6
Q

What is monocular blindness?

A

Loss of complete vision in 1 eye

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7
Q

What lesion causes monocular blindness?

A

Lesion of the optic nerve on the ipsilateral side

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8
Q

Why may monocular blindness occur?

A

Optic nerve glioma
Retinoblastoma
Trauma
Optic sheath meningioma

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9
Q

What is bitemporal hemianopia?

A

Loss of temporal fields of vision in both eyes

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10
Q

What is bitemporal hemianopia also known as?

A

Tunnel vision

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11
Q

Where is the lesion to get bilateral hemianopia?

A

Optic chiasm affecting both nasal fibres

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12
Q

What may cause a bilateral hemianopia?

A

Pituitary tumour

Anterior communicating artery aneurysm

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13
Q

What is homonymous hemianopia?

A

Loss of vision on 1 side of the eye in both eyes

Eg. Temporal in left eye and nasal in right eye- cannot see left portion of vision

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14
Q

What lesion would cause homonymous hemianopia?

A

Lesion in the optic tract

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15
Q

What causes homonymous hemianopia?

A

Neoplasia
Stroke
Trauma

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16
Q

What is macular sparing?

A

The macula in the centre of the vision is spared on the side where vision is lost.

17
Q

Why does macular sparing occur?

A

The occipital lobe has dual blood supply from the posterior cerebral artery and the middle cerebral artery. If the PCA is lost after a stroke, vision will be affected, but the MCA supplies the macula so vision centrally is spared.

18
Q

What field of vision do the inferior fibres supply?

A

Superior field of vision

19
Q

What field of vision do the superior fibres supply?

A

Inferior field of vision

20
Q

What visual loss occurs if only superior/inferior fibres are lost?

A

Quadrantanopia

21
Q

Describe the light reflex

A

Light enters eye and is picked up by the optic nerve. It goes to the Edinger-Westphal nucleus bilaterally. Both oculomotor nerves are stimulated to contract the pupils

22
Q

Describe the accommodation reflex

A

For near vision:
The eyes converge (medial rectus)
The pupils constrict (constrictor pupillae)
The lens becomes convex (ciliary muscle)

23
Q

Give 4 causes of diplopia

A 
Cataracts
Myasthenia gravis
Diabetes
MS
Stroke
Space-occupying lesion in brain --> raised intracranial pressure

semester 5- neurology (18 decks)

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