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Flashcards in Visual field defects Deck (30)
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1

visual field defects - types

1. (right/left) anopia
2. Bitemporal hemianopia
3. (left/right) homonymous hemianopia
4. (left/right) upper quadrantic anopia
5. (left/right) lower quadrantic anopia
6. (left/right) hemianopia with macular sparing
7. Central scotoma

2

Central scotoma is caused by

macular degeneration

3

(right or left) anopia?

total blindness of left or right eye

4

(right or left) anopia - mechanism

complete lesion of the right or left optic nerve

5

bitemporal hemianopia?

vision is missing in the outer half of both the right and left visual field.

6

bitemporal hemianopia is caused by

pressure exerted on the optic chiasm by a pituitary tumor

7

(left or right) homonymous hemianopia is a

visual field loss on the left or right side of the vertical midline

8

(left or right) homonymous hemianopia is caused by

1. a lesion in (left or right) of the left optic tract
2. a complete lesion in (left or right) of the left optic radiation

9

(left of right) hemianopia with macular sparing is caused by

posterior cerebral artery occlusion (Lesion of the occipital cortex)

10

left upper quadrantic anopia is caused by

1. partial involvement of the optic radiation (Meyer loop) by a lesion in the right temporal lobe
2. Middle cerebral artery stroke

11

Mayer loop contains fibers from the

inferior retina (superior part of the visual field)

12

Mayer loop pathway

through the temporal lobe by looping around the inferior horn of the lateral ventricle

13

left lower quadrantic anopia is caused by

1. partial involvement of the optic radiation (dorsal optic radiation) by a lesion in the left parietal lobe
2. Middle cerebral artery stroke

14

dorsal optic radiation

Fibers from the superior retina (inferior part of the visual field)

15

dorsal optic radiation - pathway

takes shortest path (through the parietal lobe) via internal capsule

16

Calcarine sulcus function

primary visual cortex (V1) is concentrated

17

medial longitudinal fasciculus (MLF) is a

pair of tracts that allows for crosstalk between CN VI and the contralateral CN III nuclei

18

medial longitudinal fasciculus (MLF) - function

it coordinates both eyes to move in same horizontal direction

19

medial longitudinal fasciculus (MLF) - speed of communication (and mechanism and why)

highly myelinated --> to communicate quickly so eyes move at the same time

20

medial longitudinal fasciculus (MLF) - highly myelinated
-->...

to communicate quickly so eyes move at the same time

21

bilateral medial longitudinal fasciculus (MLF) - classically seen in

multiple sclerosis

22

medial longitudinal fasciculus (MLF) - it coordinates both eyes to move in same horizontal direction - mechanism

when looking left, the left nucleus of CN VI fires, which contracts the left lateral rectus and stimulates the contralateral (right) nucleous of CN III (via the MLF) to contract the right medial rectus

23

lesion in medial longitudinal fasciculus (MLF) -->

internuclear ophthalmoplegia (INO)

24

internuclear ophthalmoplegia - mechanism

Lack of communication such that when CN VI nucleous activates ipsilateral lateral rectus, contralateral CN III nucleous does not stimulate medial rectus to fire, and the abducting eye gets nystagmous (CN VI overfires to stimulate III) --> the Convergense is normal

25

internuclear ophthalmoplegia - the abducting eye gets nystagmous - mechanism

CN VI overfires to stimulate CN III

26

directional term for internuclear ophthalmoplegia (e.g. right INO, left INO)

refers to which eye is paralysed

27

internuclear ophthalmoplegia - convergence?

normal

28

internuclear ophthalmoplegia usually implies

intrinsic brainstem disease

29

MCC of unilateral internuclear ophthalmoplegia

stroke

30

disease that can mimic a lesion of the medial longitudinal fasciculus

myasthenia gravis