wk2: ND - Brain lesions causing visual field defects

Question 1

List 3 possible locations of a lesion if it is post-chiasmal

Answer 1

Parietal lobe
Occipital lobe
Other

Question 2

List 4 descriptors of visual field loss arising from brain origin

Answer 2

Side (R or L)
Nature (homonymous or bitemporal, binasal)
Congruity (similarity e.g. in terms of severity)
Type (e.g. hemianopia, sup or inf quandrantanopia or sectoranopia)

Question 3

How can you differentiate a non-glaucomatous visual field loss from a glaucomatous one?

Answer 3

Non-glaucomatous defects generally stop when they reach the vertical midline (in fundus) rather than the horizontal one

i.e. a glaucoma defect will NOT respect this vertical midline

Question 4

Where is a visual field defect most likely located if it respects the vertical midline?

Answer 4

Posterior to chiasm (post-chiasmal, so further up in visual pathway) (could even just be chiasmal too based on lecture slides)

Question 5

Where is a visual field defect most likely located if it respects the horizontal midline?

Answer 5

Anterior to chiasm (so pre-chiasmal, think optic nerve, retina)

Question 6

What type of pattern is shown by visual field loss from optic nerve defects?

Answer 6

Arcuate patterns

Question 7

What are visual field defects in the arcuate region called (when isolated)?

Answer 7

Bjerrum scotoma

Question 8

What are visual field defects in the arcuate region called (when joined with BS)?

Answer 8

Arcuate

Question 9

How does early loss of superficial GCs affect ONH appearance? (2)

Answer 9

steep cup with notch paracentral to Bjerrum scotoma

Question 10

How does an early loss of deep GCs affect ONH appearance? (2)

Answer 10

honeycomb and “saucerised” cup and Bjerrum scotom with nasal step

Question 11

Can retinal visual field defects cross the midlines?

Answer 11

yes

Question 12

What does a retinal visual field defect involve if it respects the horizontal midline? (1)

Answer 12

RGCs

Question 13

What do altitudinal visual field defects usually indicate for?

Answer 13

ischaemia for one pole of the ONH

Question 14

Where might be responsible for a banana visual field defect? (2)

Answer 14

Optic Nerve or
Retina

Question 15

What should you consider first when you see steep sided total peripheral visual field loss?

Answer 15

Could be functional (i.e. consciously or unconsciously deciding they can’t see in certain regions)

Question 16

True/False: Defects at or beyond the chiasm will affect the VF in both eyes

Answer 16

True

Question 17

List 3 possible locations of a lesion if it is chiasmal

Answer 17

Chiasm
Optic tract
LGN

Question 18

Explain the reasoning behind why lesions at certain locations respect certain midlines?

Answer 18

Has to do with the optic nerve fibres, which travel the shortest path they need to get where they need to go

Question 19

What type of defect does Band (bowtie) optic atrophy indicate for?

Answer 19

Optic tract lesion in the contralateral optic tract, involving crossed retinal fibres nasal to the fovea (e.g. long standing pituitary lesion)

Question 20

Are people with bitemporal hemianopia symptomatic? Explain

Answer 20

Sort of, yeah. Total chiasmal VF hemi-defect can give a hemifield slide due to the loss of fusion (such as with hyper/eso/exphoria), and this can manifest as the patient’s habitual heterophoria

Physiologically, nasal and temporal visual fields overlap between the right and left eyes and allows corresponding retinal points to be established. Fusion allows the two images, one from each eye to be combined into one coherent image.[1][2] Heteronymous hemianopic defects disrupts this fusion due to the absence of right and left visual field overlap and makes maintaining stable orthotropia difficult.[3] Manifestation of horizontal or vertical tropia/phoria causes the hemifields to slide vertically or horizontally respective to one another, resulting in diplopia.[1][3]

Question 21

Define “hemifield slide”

Answer 21

Hemifield slide describes the phenomenon of inability to stabilise and fuse visual hemifields in the setting of heteronymous visual field loss.1,2 This presumably results from loss of corresponding retinal points in the two eyes, allowing an underlying phoria to manifest as a tropia, or instability of ocular alignment.

Question 22

Where does a “pie in the sky” VF defect come from?

Answer 22

Temporal lobe

(note: pie in the sky is a superior vf defect obv)
(note: not to be confused with Arnie pie in the sky, from the simpsons)

Question 23

Where does a “pie on the floor” VF defect come from?

Answer 23

Parietal lobe

Question 24

Why might a patient be unaware of VF defect? (1) What must you do to ensure no VF defect? (1)

Answer 24

Foveal sparing. Do confrontation on everyone

Question 25

Define the Riddoch phenomenon. What kind of lesions can it occur in?

Answer 25

Perception of movement but loss of form. Can occur in occipital lobe lesions

Question 26

How might the Riddoch phenomenon be found in a patient?

Answer 26

Loss in static perimetry but normal kinetic perimetry

Question 27

Define cortical blindness. What happens to the artery involved?

Answer 27

Total blindness due to bilateral occipital lobe lesions. Bilateral infarcts of basilar artery

Question 28

How will an (adult) patient with cortical blindness present after testing in your clinic? (6)

Answer 28

Pupils: ok
ERG: ok
VER: abnormal
May have residual motion perception (“blindsight”)
Fundus: normal
May have visual percepts (CBS, charles bonnet) and deny

Question 29

Is hallucination possible with cortical blindness?

Answer 29

Yep

Question 30

Describe the procedure for testing for corticalVF loss. What does it indicate for? What can happen with chronic cases?

Answer 30

Amsler grid
Indicates for scotoma
Cortical filling occurs with chronic cases

Question 31

What two things is simultaneous confrontation good for and not good for?

Answer 31

Good:
Screening and testing large perpheral defects
Sensitivity
Not good:
Retinal or optic lesions
Small defects