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OV2004 clinical skills > Visual fields ||| > Flashcards

Visual fields ||| Flashcards

1
Q

what are the instructions to give your patient before a visual field test ?

A

. this test will test all the areas you can see with each eye
. cover one 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. Every time you see a light press your button (show them )
. you will not see all the lights
. the most important thing to remember is to always keep watching the fixation light in the centre

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2
Q

how to improve accuracy with your patient?

A

. ensure they are comfortable

  • neck/head position
  • coat on or off

. explain how long it will take
-(XX no. of minutes)

. patient can pause the test on a Humphrey

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3
Q

what are visual field defects ?

A
  • visual field defect is defined as a departure from the topography of the hill of vision from the normal limits
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4
Q

why is it important to accurately describe the type of visual field defect ?

A
  • helps determine the type of pathology

- helps to monitor the condition

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5
Q

what is a localised defect ?

A
  • could also be called a scotoma

- small area of localised visual field loss

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6
Q

what is a depression or diffuse visual field loss ?

A
  • a generalised reduction in the height of the hill of vision
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7
Q

what is the contraction of the visual field ?

A

. the entire visual field is constructed

. could also be referred to as constriction of the visual field

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8
Q

what is absolute scotoma ?

A
  • the scotoma is absolute when the patient can see absolutely nothing inside this scotoma
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9
Q

what is relative scotoma?

A
  • the patient has a loss of visual field but can see something in this area of loss
  • they can’t see what the average normal person of that age can see
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10
Q

what is a scotoma with steep margin ?

A
  • px can see normal for their age until they suddenly cannot see
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11
Q

what is a scotoma with sloping margin ?

A
  • px can see normal for their age, then they can see a little less normal for their age until they can’t see anything
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12
Q

what is hemianopia ?

A
  • half visual defect
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13
Q

what is an altitudinal hemianopia ?

A
  • defect will be either on the superior half of the visual field or the inferior half of the visual field
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14
Q

what is hemianopic defect with macula sparing ?

A
  • the macula will be spared
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15
Q

what does it mean when hemianopic defect has a macula splitting?

A
  • the hemianopia will split macula in half
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16
Q

what is quadrantanopia ?

A
  • quadrant visual field defect
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17
Q

how do we measure central visual field ?

A
  • by measuring the central 30 degrees
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18
Q

what is central scotoma ?

A
  • scotoma that encompasses the fixation point ( fovea)
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19
Q

what is pathology that causes a central scotoma ?

A
  • AMD
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20
Q

what is pericentral scotoma ?

A
  • px will have visual field defect that surrounds the fovea , surrounds the fixation point
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21
Q

what is paracentral scotoma?

A
  • visual field defect that is adjacent to the fovea

- adjacent to fixation point

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22
Q

what is centrocecal scotoma?

A
  • visual defect that extends from fixation point in centre all the way to blind spot
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23
Q

what is baring of the blind spot?

A
  • visual field defect that revealed the blind spot
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24
Q

what nasal step ?

A
  • defect in nasal visual field
  • nasal step will never cross the horizontal line
  • where the blind spot is temporal and so the nasal will be on the opposite side
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25
Q

what is arcuate scotoma?

A
  • scotoma that looks like an arc
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26
Q

what is ring scotoma?

A
  • scotoma that looks like a ring

- can say it is a constriction or contraction of the visual field

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27
Q

what is homonymous hemianopia?

A
  • the same side / half visual field defect (for e.g heminaopia on the right side of the right eye and the right side of the left eye)
  • the visual field defect is on the same side on both eyes
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28
Q

what does px experience when having right homonymous hemianopia ?

A
  • px would see nothing then suddenly something will appear from the side
29
Q

what is partial homonymous hemianopia?

A
  • only part of half visual field defect is missing
30
Q

what is complete homonymous hemianopia?

A
  • visual field defect would come all the way up to the midline- across the macula which would mean also macula splitting
31
Q

what is homonymous hemianopia with macula sparing?

A
  • visual defect would come all the way to midline but spare the macula
32
Q

what is bitemporal hemianopia?

A
  • also know as heteronymous hemianopia because on right on right eye and left on the left eye
  • visual field defect is temporal on both eyes
33
Q

what is binasal hemianopia?

A
  • also known heteronymous because its on the left of RE and right of LE
  • visual field defect is nasal on both eyes
34
Q

what is a congruous defect ?

A
  • mirror image of the opposite eye in terms of size, shape and symmetry
  • whatever the defect is exactly the same in the other eye too.
35
Q

what is incongruous defect?

A
  • defect looks different in terms of size, shape and symmetry in the both eyes
36
Q

what does every point in the retina correspond to?

A
  • every point in the retina corresponds to a certain direction in the visual field
  • e.g. nasal retina always corresponds to a temporal visual field
37
Q

where would defect in inferior nasal retina be see in visual field ?

A
  • defect will be seen in superior temporal retina

- opposite side to retina

38
Q

where the px right fundus ?

A

on the clinician left side

39
Q

where the px left fundus ?

A

on the clinician right side

40
Q

where is the visual field seen ?

A
  • what the patient sees
  • right visual field on right
  • left visual field on the left
41
Q

what retina visual pathway broken into ?

A 
. superior temporal fibres
. superior nasal fibres
. inferior temporal fibres
. inferior nasal fibres
. macular fibres
42
Q

where are nerve fibres mostly vulnerable ?

A
  • they are tightly packed around the optic disc

- this means they are vulnerable to pressure changes in the eye and vascular changes in eye

43
Q

what do nerve fibres of optic disc supply?

A
  • supply the superior temporal retina
44
Q

what happens if there is defect to nerve fibres that supply superior temporal retina?

A
  • because they supply superior temporal retina , the defect will be a inferior nasal defect
  • cause an arcuate scotoma
45
Q

what do nerve fibres not do ?

A

they do not cross horizontal line so neither would the defect- if there was one .

46
Q

where is another place the fibres are tightly packed ?

A

. in the inferior part

47
Q

what do inferior nerve fibres supply?

A
  • supply inferior temporal retina
48
Q

what happens if there is a defect in inferior temporal retina?

A
  • there will be a superior nasal visual field defect
  • paracentral scotomas
  • typical in what causes glaucoma
49
Q

what is a nasal step ?

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 form the inferior rim ( 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
50
Q

what are the rules of retinal lesions such as central retinal vein occlusion?

A
  • can be unilateral or bilateral
  • often asymmetrical between eyes
  • do not respect the vertical midline and does cross over it
51
Q

what nerve fibres cross the optic chiasm ?

A
  • macular fibres cross

- nasal fibres cross

52
Q

which nerve fibres do not cross the optic chiams ?

A
  • temporal fibres do not cross
53
Q

what does an optic nerve lesion of RE mean ?

A
  • lesion has taken out all temporal and nasal fibres of RE

- px can see nothing with RE

54
Q

what does an optic chiasm lesion mean ?

A
  • lesion taken out nasal fibres of RE and LE
  • the temporal visual field is absent from the RE
  • the temporal visual field is absent from LE
  • bi-temporal hemianopia
  • its crossed
55
Q

what does an LE lesion of optic tract mean?

A
  • lesion taken out temporal fibres from LE - and temporal fibres supply nasal visual field therefore
  • nasal visual field is gone from LE
  • lesion also taken out nasal fibres from RE because nasal fibres cross
  • this means temporal visual defect in RE
  • this causes homonymous hemianopia
56
Q

what are the rules for analysing VF?

A
  • unilateral field defect usually involves damage anterior/before the to the chiasm
  • a field defect which respects the vertical meridian suggests chiasmal or posterior to the chiasm - defect will be at the chiasm or at the posterior
  • heteronymous defect suggests chiasmal defect
  • homoymous defect suggest posterior to the chiasm
57
Q

what happens if there is a lesion in the left hemisphere?

A
  • lesion will take out temporal fibres from the left eye
  • temporal fibres project nasally
  • nasal visual field defect
  • lesion will affect nasal fibres from RE
  • nasal fibres from RE project temporally
  • the patient will have temporal defect in RE
  • this causes a right visual field defect
58
Q

what happens if the pathology was above inion ?

A
  • will cause an inferior visual field defect

- the scotoma was in the inferior visual field

59
Q

what happens if pathology was on the left cerebral hemisphere?

A
  • the scotoma was on the right, and vice versa
60
Q

what is V1 cortical magnification?

A
  • 60% of V1 relates to macula
61
Q

what happens if you have a lesion on the tip of the occipital lobe ?

A
  • will cause a macular

- defect congruent

62
Q

what happens if you have anterior lesion?

A
  • will spare the macula

- will cause incongruent defect

63
Q

is the visual field loss unilateral or bilateral?

A
  • unilateral not likely to be neurological
  • before chisasm- like a retinal defect
  • post chiasm will result in a bilateral defect
64
Q

what does it mean if field respects vertical chiasm?

A

suggest chiasmal or retrochiasmal(after chiasm) defect

65
Q

is the defect homoymous or heteronymous?

A
  • heteronymous suggest chiasmal

- homonymous suggest retrochismal

66
Q

of homonymous which side of the field is affected?

A
  • left VFD lesion right side of the brain
  • right VFD lesion left side of the brain
  • parietal lobe ( superior retinal fibres) inferior VFD
  • above inion ( superior retinal fibres) inferior VFD
  • temporal lobe ( inferior retinal fibres ) superior VFD
  • below inion superior VFD
67
Q

is the defect congruous or affecting the macula?

A
  • more congruent the more posterior - right back in occipital lobe
  • affecting macula more posterior- also in the occipital lobe tips
68
Q

what happens if the pathology was below the inion ?

A

it would cause a superior visual defect

69
Q

What would a unilateral defect be ?

A

more likely to be anterior to chiasm- something like retinal defect
-does not respect the vertical midline - suggesting it is a retinal defect.

OV2004 clinical skills (12 decks)

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