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
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
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
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
5
Q
what is a localised defect ?
A
- could also be called a scotoma
- small area of localised visual field loss
6
Q
what is a depression or diffuse visual field loss ?
A
- a generalised reduction in the height of the hill of vision
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
8
Q
what is absolute scotoma ?
A
- the scotoma is absolute when the patient can see absolutely nothing inside this scotoma
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
10
Q
what is a scotoma with steep margin ?
A
- px can see normal for their age until they suddenly cannot see
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
12
Q
what is hemianopia ?
A
- half visual defect
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
14
Q
what is hemianopic defect with macula sparing ?
A
- the macula will be spared
15
Q
what does it mean when hemianopic defect has a macula splitting?
A
- the hemianopia will split macula in half
16
Q
what is quadrantanopia ?
A
- quadrant visual field defect
17
Q
how do we measure central visual field ?
A
- by measuring the central 30 degrees
18
Q
what is central scotoma ?
A
- scotoma that encompasses the fixation point ( fovea)
19
Q
what is pathology that causes a central scotoma ?
A
- AMD
20
Q
what is pericentral scotoma ?
A
- px will have visual field defect that surrounds the fovea , surrounds the fixation point
21
Q
what is paracentral scotoma?
A
- visual field defect that is adjacent to the fovea
- adjacent to fixation point
22
Q
what is centrocecal scotoma?
A
- visual defect that extends from fixation point in centre all the way to blind spot
23
Q
what is baring of the blind spot?
A
- visual field defect that revealed the blind spot
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
25
what is arcuate scotoma?
- scotoma that looks like an arc
26
what is ring scotoma?
- scotoma that looks like a ring
| - can say it is a constriction or contraction of the visual field
27
what is homonymous hemianopia?
- 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
28
what does px experience when having right homonymous hemianopia ?
- px would see nothing then suddenly something will appear from the side
29
what is partial homonymous hemianopia?
- only part of half visual field defect is missing
30
what is complete homonymous hemianopia?
- visual field defect would come all the way up to the midline- across the macula which would mean also macula splitting
31
what is homonymous hemianopia with macula sparing?
- visual defect would come all the way to midline but spare the macula
32
what is bitemporal hemianopia?
- 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
what is binasal hemianopia?
- also known heteronymous because its on the left of RE and right of LE
- visual field defect is nasal on both eyes
34
what is a congruous defect ?
- 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
what is incongruous defect?
- defect looks different in terms of size, shape and symmetry in the both eyes
36
what does every point in the retina correspond to?
- 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
where would defect in inferior nasal retina be see in visual field ?
- defect will be seen in superior temporal retina
| - opposite side to retina
38
where the px right fundus ?
on the clinician left side
39
where the px left fundus ?
on the clinician right side
40
where is the visual field seen ?
- what the patient sees
- right visual field on right
- left visual field on the left
41
what retina visual pathway broken into ?
```
. superior temporal fibres
. superior nasal fibres
. inferior temporal fibres
. inferior nasal fibres
. macular fibres
```
42
where are nerve fibres mostly vulnerable ?
- 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
what do nerve fibres of optic disc supply?
- supply the superior temporal retina
44
what happens if there is defect to nerve fibres that supply superior temporal retina?
- because they supply superior temporal retina , the defect will be a inferior nasal defect
- cause an arcuate scotoma
45
what do nerve fibres not do ?
they do not cross horizontal line so neither would the defect- if there was one .
46
where is another place the fibres are tightly packed ?
. in the inferior part
47
what do inferior nerve fibres supply?
- supply inferior temporal retina
48
what happens if there is a defect in inferior temporal retina?
- there will be a superior nasal visual field defect
- paracentral scotomas
- typical in what causes glaucoma
49
what is a nasal step ?
- 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
what are the rules of retinal lesions such as central retinal vein occlusion?
- can be unilateral or bilateral
- often asymmetrical between eyes
- do not respect the vertical midline and does cross over it
51
what nerve fibres cross the optic chiasm ?
- macular fibres cross
| - nasal fibres cross
52
which nerve fibres do not cross the optic chiams ?
- temporal fibres do not cross
53
what does an optic nerve lesion of RE mean ?
- lesion has taken out all temporal and nasal fibres of RE
| - px can see nothing with RE
54
what does an optic chiasm lesion mean ?
- 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
what does an LE lesion of optic tract mean?
- 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
what are the rules for analysing VF?
- 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
what happens if there is a lesion in the left hemisphere?
- 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
what happens if the pathology was above inion ?
- will cause an inferior visual field defect
| - the scotoma was in the inferior visual field
59
what happens if pathology was on the left cerebral hemisphere?
- the scotoma was on the right, and vice versa
60
what is V1 cortical magnification?
- 60% of V1 relates to macula
61
what happens if you have a lesion on the tip of the occipital lobe ?
- will cause a macular
| - defect congruent
62
what happens if you have anterior lesion?
- will spare the macula
| - will cause incongruent defect
63
is the visual field loss unilateral or bilateral?
- unilateral not likely to be neurological
- before chisasm- like a retinal defect
- post chiasm will result in a bilateral defect
64
what does it mean if field respects vertical chiasm?
suggest chiasmal or retrochiasmal(after chiasm) defect
65
is the defect homoymous or heteronymous?
- heteronymous suggest chiasmal
| - homonymous suggest retrochismal
66
of homonymous which side of the field is affected?
- 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
is the defect congruous or affecting the macula?
- more congruent the more posterior - right back in occipital lobe
- affecting macula more posterior- also in the occipital lobe tips
68
what happens if the pathology was below the inion ?
it would cause a superior visual defect
69
What would a unilateral defect be ?
more likely to be anterior to chiasm- something like retinal defect
-does not respect the vertical midline - suggesting it is a retinal defect.
