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Clinical Skills Year 2 > visual fields lec 3: vf defects, where is the pathology? > Flashcards

visual fields lec 3: vf defects, where is the pathology? Flashcards

1
Q

list how you will instruct your patient when setting them up on the visual fields machine

A
  • this test will test all the area you can see with each eye
  • i want you to always look straight ahead at the fixation light in the centre (show them)
  • other lights will now flash in different places. overtime you see a light press your button
  • you will not see all the lights (px might panic)
  • the most important thing to remember is to always keep watching the fixation light in the centre (don’t look away)
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2
Q

list the three ways that you can increase accuracy with your patient

A
  1. ensure they are comfortable
    - neck/head position
    - coat on or off
  2. explain how long it will take
    - xx no. of minutes
    - let them know how far along they are
  3. patient can pause the test on a humphrey
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3
Q

what is a visual field defect defined as

A

a departure from (normal position) the topography of the hill of vision from normal limits

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4
Q

what are the two reasons that it is important to accurately describe the type of visual field defect

A
  1. helps to determine the type of pathology it can be

2. helps to monitor the condition

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5
Q

what is the name for a localised defect (area of vision loss)

A

scotoma

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6
Q

what is a generalised reduction in the height of the hill of vision defined as

A

a depression or diffuse visual field loss

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7
Q

what is the contraction of the visual field

A

when you lose the visual field from the outside going to the inside

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8
Q

what are the 2 types of scotomas and describe them

A
  1. absolute: can see absolutely nothing (in that region)

2. relative: not normal, but can see something

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9
Q

what are the two types of margins of a scotoma and describe them

A
  1. steep: from normal to nothing

2. sloping: can see normal, then gradually less

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10
Q

what type of hemianopia is a altitudinal hemianopia

A

superior or inferior hemianopia

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11
Q

what is macula sparing

A

when you can still see the visual field corresponding to the macula (central vision)

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12
Q

what is macula splitting

A

the macula is split into half (half is affected and half is not, so you can see half of your central vision and not the other half through the eye affected)

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13
Q

what is quadtranopia

A

a quadrant of the visual field is affected

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14
Q

list the 4 types of central visual field loss and describe them

A
  1. central scotoma: affects fovea fixation point
  2. pericentral scotoma: surrounds fovea but does cover it
  3. paracentral scotoma: adjacent to the fixation point
  4. centrocecal scotoma: extends from fixation point to blind spot
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15
Q

what is meant by baring of the blind spot

A

the visual field reveals the blind spot

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16
Q

what is meant by nasal step

A

a superior nasal visual field defect which will not cross the horizontal midline, this is classic of glaucoma

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17
Q

which condition is a nasal step classic in

A

glaucoma

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18
Q

what is a arcuate scotoma

A

a scotoma with an arc shape

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19
Q

what is a ring scotoma

A

looks like a ring or contraction of the visual field

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20
Q

describe a homonymous hemianopia

A

half of the visual field is affected on the same side or each eye

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21
Q

what is a partial homonymous hemianopia

A

when the half of the visual field defect doesn’t go up to the midline

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22
Q

what is a complete homonymous hemianopia

A

when the half of the visual field defect does go up to the midline

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23
Q

what are the three types of homonymous hemianopia

A
  • partial
  • complete
  • with macula sparing
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24
Q

what is a bitemporal hemianopia

A

when the temporal half of visual field of each eye is affected

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25
Q

what is another name for a hemianopia on the opposite sides of visual field of each eye

A

heteromonous hemianopia

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26
Q

what is a binasal hemianopia

A

when the nasal half of visual field of each eye is affected

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27
Q

what is a congruous defect

A

when the visual defect is the same shape and size as the other eyes, i.e. there is symmetry

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28
Q

what is the name of a defect which is asymmetrical to the other eye’s vf defect i.e. asymmetrical to one another

A

incongruous

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29
Q

what knowledge will enable you to localise the visual field defect

A

the knowledge of the arrangement of the nerve fibres in the visual pathway

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30
Q

what does every point on the retina correspond to

A

a certain direction in the visual field

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31
Q

what is the retinal image in relation to the visual field

A

retinal image is upside down and back to front

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32
Q

where in the retinal image is a superior temporal visual field

A

inferior nasal

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33
Q

where in the retinal image is a superior nasal visual field

A

inferior temporal

34
Q

where in the retinal image is a inferior nasal visual field

A

superior temporal

35
Q

where in the retinal image is a inferior temporal visual field

A

superior nasal

36
Q

from a clinician’s point of view, which side is the optic nerve on in a patient’s right fundus

A

on the right hand side

37
Q

from a clinician’s point of view, which side is the optic nerve on in a patient’s left fundus

A

on the left hand side

38
Q

which side of the clinician will a patient’s right fundus be

A

on the left hand side of the clinician

39
Q

which side of the clinician will a patient’s left fundus be

A

on the right hand side of the clinician

40
Q

which side will a patient’s blind spot be in the left eye

A

their left hand side

41
Q

which side will a patient’s blind spot be in the right eye

A

their right hand side

42
Q

how many retinal ganglion cells are at the macula

A

66-75%

43
Q

what is the vertical demarcation line

A

a vertical line that divides the nasal and temporal retina

44
Q

what is the horizontal raphe

A

a horizontal line that divides the superior and inferior retina

45
Q

in which part of the retina are the axons most crowed

A

the papillomacular bundle

46
Q

which retinal fibres are damaged if you have a inferior arcuate scotoma

A

damage of superior temporal retina

47
Q

what is the cause within the retina of a nasal step visual field defect

A

the fibres at the rim are the most crowded at the disc, providing less structural and vascular support and are the most likely to become damaged in glaucoma.

the fibres from the inferior rim (which are most commonly affected) supply the inferior temporal retina. damage to this area corresponds to the superior nasal visual field defect.

the areas supplied by the fibres correspond to the nasal step and do not cross the horizontal raphe.

48
Q

name the three rules for visual field assessment from retinal lesions

A
  1. can be unilateral or bilateral (does not always affect both eyes)
  2. often asymmetrical between eyes (looks different)
  3. do not respect the vertical midline (passes over it)
49
Q

give an example of a retinal lesion which can cause a visual field defect

A

when a vein gets occluded and bleeds out

50
Q

which fibres cross and which do not cross at the optic chiasm

A
  • macular fibres cross
  • nasal fibres cross
  • temporal fibres do not cross
    at the optic chiasm
51
Q

what is the visual field defect when there is a full lesion of the right optic nerve

A

right unilateral full field defect
right visual field no light perception
no direct pupil reflex RE
left visual field is full

52
Q

what is the visual field defect when there is a lesion to the middle (nasal fibres) of the optic chiasm

A

heteronymous bi-temporal hemianopia

53
Q

what is the visual field defect when there is a lesion to the left optic tract

A

right homonymous hemianopia

54
Q

which fibres are taken out when there is a lesion to the left optic tract

A

temporal fibres of the left eye and nasal fibres of the right eye

55
Q

which type of visual field defect occurs before the/anterior to the optic chiasm

A

unilateral (one side) field defect

56
Q

what does a field defect which respects the vertical meridian suggest about the lesion

A

that the lesion is chiasmal or posterior to the chiasm

57
Q

what are homonymous defects always posterior to

A

always posterior to the chiasm
e.g. a lesion in the left hemisphere takes out temporal fibres of of the left eye causing a nasal defect and takes out nasal fibres of the right eye which causes a temporal defect

58
Q

where will the scotoma be, if the pathology is above the inion where the superior fibres are

A

in the inferior visual field

59
Q

if the lesion is in the left cerebral hemisphere, where will the scotoma be

A

on the right hand side of visual field

60
Q

a lesion to which part of the visual pathway will there be an incongruent visual field defect

A

the optic tract

61
Q

a lesion to which part of the optic pathway will the visual field defects be more congruent

A

towards the occipital lobe, congruence increases towards the posterior cortex

62
Q

areas to which part of the occipital lobe tend to cause visual field defects with macula sparing

A

lesions to the anterior part of the occipital lobe (where the macula is not represented)

63
Q

if the visual field defect is unilateral (one eye), what is the cause most likely NOT to be

A

neurological

64
Q

a lesion to which part of the optic pathway will cause a bilateral lesion

A

posterior to the optic chiasm

65
Q

what does a visual field loss that respects the vertical meridian suggest about the lesion

A

that the lesion is chiasmal or retrochiasmal (beyond the chiasm)

66
Q

if a visual field defect is heteronymous, what does it suggest about the location of the lesion

A

that the lesion is chiasmal

67
Q

if a visual field defect is homonymous, what does it suggest about the location of the lesion

A

it is retro chiasmal (beyond the chiasm)

68
Q

a lesion to which side of the brain causes a homonymous left visual field defect

A

lesion to right side of the brain

69
Q

a lesion to which side of the brain causes a homonymous right visual field defect

A

lesion to left side of the brain

70
Q

a lesion to which 2 parts of the brain causes a homonymous inferior visual field defect

A
  • lesion to:
  • the parietal lobe superior retinal fibres
  • above the inion superior retinal fibres
71
Q

a lesion to which 2 parts of the brain causes a homonymous superior visual field defect

A

lesion to:

  • temporal lobe inferior retinal fibres
  • below the inion inferior retinal fibres
72
Q

a lesion to which region of the optic pathway will cause a more congruent visual field defect

A

the more posterior, the more congruent

73
Q

a lesion to which part of the optic pathway will more likely affect the macula visual field

A

the more posterior part of the occipital lobe

74
Q

list 4 aspects of a visual field defect you expect to find on a patient who has glaucoma

A
  • paracentral scotomas
  • enlargement of the blind spot
  • nasal step (doesn’t cross the horizontal midline)
  • arcuate scotomas
75
Q

what type of visual field defect will a lesion anterior to the chiasm cause

A

a unilateral defect which doesn’t respect the vertical midline

76
Q

what time of visual defect will a lesion at or posterior to the chiasm cause

A

bilateral and respects the vertical midline

77
Q

will a homonymous defect be caused by a lesion posterior or anterior to the optic chiasm

A

posterior to the optic chiasm

78
Q

if the visual field defect is incongruent and the macula is spared, which part of the cortex is affected

A

the anterior region e.g. more towards the temple lobe

79
Q

give a full description of a visual field defect caused by a left temporal lobe lesion

A

right homonymous, incongruent hemianopia with macula sparing and predominantly affecting the upper visual field

80
Q

where is the lesion if the visual field defect description is: left homonymous inferior quadrantopia, congruent also affecting the macula

A

right posterior occipital lobe lesion

Clinical Skills Year 2 (20 decks)

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