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

Question 1

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

Answer 1

• 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)

Question 2

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

Answer 2

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

Question 3

what is a visual field defect defined as

Answer 3

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

Question 4

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

Answer 4

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

2. helps to monitor the condition

Question 5

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

Answer 5

scotoma

Question 6

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

Answer 6

a depression or diffuse visual field loss

Question 7

what is the contraction of the visual field

Answer 7

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

Question 8

what are the 2 types of scotomas and describe them

Answer 8

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

2. relative: not normal, but can see something

Question 9

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

Answer 9

1. steep: from normal to nothing

2. sloping: can see normal, then gradually less

Question 10

what type of hemianopia is a altitudinal hemianopia

Answer 10

superior or inferior hemianopia

Question 11

what is macula sparing

Answer 11

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

Question 12

what is macula splitting

Answer 12

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)

Question 13

what is quadtranopia

Answer 13

a quadrant of the visual field is affected

Question 14

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

Answer 14

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

Question 15

what is meant by baring of the blind spot

Answer 15

the visual field reveals the blind spot

Question 16

what is meant by nasal step

Answer 16

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

Question 17

which condition is a nasal step classic in

Answer 17

glaucoma

Question 18

what is a arcuate scotoma

Answer 18

a scotoma with an arc shape

Question 19

what is a ring scotoma

Answer 19

looks like a ring or contraction of the visual field

Question 20

describe a homonymous hemianopia

Answer 20

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

Question 21

what is a partial homonymous hemianopia

Answer 21

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

Question 22

what is a complete homonymous hemianopia

Answer 22

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

Question 23

what are the three types of homonymous hemianopia

Answer 23

• partial
• complete
• with macula sparing

Question 24

what is a bitemporal hemianopia

Answer 24

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

Question 25

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

Answer 25

heteromonous hemianopia

Question 26

what is a binasal hemianopia

Answer 26

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

Question 27

what is a congruous defect

Answer 27

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

Question 28

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

Answer 28

incongruous

Question 29

what knowledge will enable you to localise the visual field defect

Answer 29

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

Question 30

what does every point on the retina correspond to

Answer 30

a certain direction in the visual field

Question 31

what is the retinal image in relation to the visual field

Answer 31

retinal image is upside down and back to front

Question 32

where in the retinal image is a superior temporal visual field

Answer 32

inferior nasal

Question 33

where in the retinal image is a superior nasal visual field

Answer 33

inferior temporal

Question 34

where in the retinal image is a inferior nasal visual field

Answer 34

superior temporal

Question 35

where in the retinal image is a inferior temporal visual field

Answer 35

superior nasal

Question 36

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

Answer 36

on the right hand side

Question 37

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

Answer 37

on the left hand side

Question 38

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

Answer 38

on the left hand side of the clinician

Question 39

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

Answer 39

on the right hand side of the clinician

Question 40

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

Answer 40

their left hand side

Question 41

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

Answer 41

their right hand side

Question 42

how many retinal ganglion cells are at the macula

Answer 42

66-75%

Question 43

what is the vertical demarcation line

Answer 43

a vertical line that divides the nasal and temporal retina

Question 44

what is the horizontal raphe

Answer 44

a horizontal line that divides the superior and inferior retina

Question 45

in which part of the retina are the axons most crowed

Answer 45

the papillomacular bundle

Question 46

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

Answer 46

damage of superior temporal retina

Question 47

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

Answer 47

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.

Question 48

name the three rules for visual field assessment from retinal lesions

Answer 48

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)

Question 49

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

Answer 49

when a vein gets occluded and bleeds out

Question 50

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

Answer 50

- macular fibres cross - nasal fibres cross - temporal fibres do not cross at the optic chiasm

Question 51

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

Answer 51

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

Question 52

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

Answer 52

heteronymous bi-temporal hemianopia

Question 53

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

Answer 53

right homonymous hemianopia

Question 54

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

Answer 54

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

Question 55

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

Answer 55

unilateral (one side) field defect

Question 56

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

Answer 56

that the lesion is chiasmal or posterior to the chiasm

Question 57

what are homonymous defects always posterior to

Answer 57

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

Question 58

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

Answer 58

in the inferior visual field

Question 59

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

Answer 59

on the right hand side of visual field

Question 60

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

Answer 60

the optic tract

Question 61

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

Answer 61

towards the occipital lobe, congruence increases towards the posterior cortex

Question 62

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

Answer 62

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

Question 63

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

Answer 63

neurological

Question 64

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

Answer 64

posterior to the optic chiasm

Question 65

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

Answer 65

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

Question 66

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

Answer 66

that the lesion is chiasmal

Question 67

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

Answer 67

it is retro chiasmal (beyond the chiasm)

Question 68

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

Answer 68

lesion to right side of the brain

Question 69

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

Answer 69

lesion to left side of the brain

Question 70

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

Answer 70

- lesion to: - the parietal lobe superior retinal fibres - above the inion superior retinal fibres

Question 71

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

Answer 71

lesion to: - temporal lobe inferior retinal fibres - below the inion inferior retinal fibres

Question 72

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

Answer 72

the more posterior, the more congruent

Question 73

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

Answer 73

the more posterior part of the occipital lobe

Question 74

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

Answer 74

- paracentral scotomas - enlargement of the blind spot - nasal step (doesn't cross the horizontal midline) - arcuate scotomas

Question 75

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

Answer 75

a unilateral defect which doesn't respect the vertical midline

Question 76

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

Answer 76

bilateral and respects the vertical midline

Question 77

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

Answer 77

posterior to the optic chiasm

Question 78

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

Answer 78

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

Question 79

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

Answer 79

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

Question 80

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

Answer 80

right posterior occipital lobe lesion