Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Binocular vision > Motor functions: fusional reserves & prism tests > Flashcards

Motor functions: fusional reserves & prism tests Flashcards

1
Q

define motor fusion

A

ability to align the eyes so that sensory fusion can occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what does motor fusion occur with

A

vergences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

describe how motor fusion occurs with vergences

A

the eyes must look towards/face the object of regard so that the image can fall on the fovea
eg at near eyes must converge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what must the eyes do in order to maintain BSV

A

move together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the stimulus which creates retinal disparity outside panum’s areas

A

diplopia or confusion

and when the object of regard falls out of panum’s area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is vergence

A

when the eyes move in opposite directions to one another

both visual axis needs to converge or diverge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is version

A

when the eyes move in the same direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how much degrees of fov does the fovea have

A

6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how much prism dioptre is equivalent to 6 degrees of foveal gov

A

1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how is the image placed nicely on the fovea and achieve bsv

A

when the images are very close to, it is bought about by motor fusion, you can then do final fine tuning by sensory fusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

when is motor fusion completely suspended

A

typically when the eyes converge on a plane 1 meter away

but others converge more or even diverge, so theres varience between individuals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are the 2 resting positions of mergence system

A
  • distance

- near

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what does distance vision require as a resting position

A

active divergence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what does near vision require as a resting position

A

active convergence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what must both eyes do when converging and diverging in order to achieve bsv

A

co-ordinated fashion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

list the three motor fusion for distance

A
  • position of anatomical rest
  • fusion free position
  • distance fusion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

describe the position of anatomical rest

A
  • no input from etraocular muscles
  • usually this position when closed eyes or in dark
  • mostly eyes are divergent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

describe the position of fusion free position

A

no fusion, but the patient is awake

for some it an be slightly divergent or convergent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

describe the distance fusion

A

usually takes this position when there is an object to look at.
it is a distance fusion when the visual axis becomes parallel and you get bsv

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

how is the fusion free position maintained

A

by tons of extra ocular muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

list the two types of motor fusion near

A
  • proximal convergence

- accommodative convergence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is proximal convergence

A

awareness of near object, so have to converge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is accommodative convergence

A

the blurred image (when we immediately look from distance to near) so must accommodate and converge to make the image clear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what fusions must you need to get bsv at near

A

motor & sensory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what are prisms used to assess

A

strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

if a prism is placed before the eyes of a person with strong bsv, list the things which will occur

A
  • initially diplopia is experienced
  • prism base out, eyes must converge to take up fixation
  • prism base in, eyes must diverge to take up fixation
  • prism base up before one eye and prism base down before the other measures vertical vergence
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what does prism base out do to the image, and what does the eye have to do to achieve single vision/fixation

A

moves image temporally

eye has to move in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what does prism base in do to the image, and what does the eye have to do to achieve single vision/fixation

A

moves image nasally

eye has to move out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

describe why an exodeviation is measured with a prism base out

A

we want to measure how good they are at controlling the exodeviation and how good they are at converging

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what is the level of control of latent deviation if has good motor fusion

A

good control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what is the risk of latent deviation if has poor motor fusion

A

latent deviation can become manifest

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what type of control does someone have over their latent deviation if it is small

A

good control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what type of control does someone have over their latent deviation if it is large

A

bad control even if they have good motor fusion due to it being a large deviation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what stimulates motor fusion

A

diplopia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what is the amplitude of motor fusion

A

if the image falling on corresponding retinal areas is shifted, upper limit possible of vergences in which diplopia can not be avoided

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what is the strength of bsv indicated by

A

amount of motor fusion possible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

the more prism that can tolerate…

A

the better their motor fusion, and less likely for their deviation to become manifest

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what does the essential strength of motor fusion indicate

A

the strength of BSV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

what is horizontal and vertical fusion assessed with

A

prism bar
or
Risley prism and fixation target

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

what are the fixation targets when using the prism bar and Risley prism when horizontal and vertical fusion is assessed

A

distance - snellen chart

near - budgie stick

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

why is a letter on a snellen chart used instead of a light, when assessing fusion

A

as letter produces more incentive to fuse a detailed target

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

which types of fusion is assessed with a synoptophore

A
  • horizontal
  • vertical
  • cyclofusion (sagittal axis)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what does the prism fusion range measure

A

patients ability to maintain sensory fusion through a range of vergence movements

44
Q

which sensory fusion range does base out prism measure

A

convergent fusion range

45
Q

which sensory fusion range does base in prism measure

A

divergent fusion range

46
Q

which sensory fusion does base up prism measure

A

supravergence fusion range

47
Q

which sensory fusion does base down prism measure

A

infravergence fusion range

48
Q

list the steps of how to measure prism fusion range

A
  • patient sits head erect
  • patient directed to appropriate letter 6/60
  • prism bar placed before one eye
  • strength increased slowly (start with 2 prism as thats the smallest)
  • continue increasing prism strength until patient reports diplopia
  • ask if they can make the image single (as with time they can maintain fusion & bsv through a new more prisms)
  • continue to increase prism
  • note maximum amount of prism before diplopia is recorded - break point
49
Q

what is the break point

A

the maximum amount of prism before diplopia is reported

50
Q

what may a patient complain of during relative accommodation

A

blur

51
Q

when does relative accommodation occur

A

normally when vergence changes accommodation changes by a linked amount

52
Q

give examples of how when vergence changes, accommodation changed by a linked amount

A
  • convergence increases, accommodation increases

- divergence increases, accommodation decreases

53
Q

list the types of accommodations relative to convergence

A
  • positive relative accommodation

- negative relative accommodation

54
Q

prism bar is asking to change vergence without….

A

changing accommodation, which can do initially but as increase the prism, their accommodation is going to kick in and will report that the target is blurred

55
Q

what do you record when recording the prism fusion range of a px

A
  • break
  • distance
  • base direction
56
Q

give an example of recording a prism fusion range of a px

A

near PFR
base in 18
base out 28

57
Q

what happens to the eyes when placing a base out prism infront of left eye

A
  • left eye moves in

- right eye will move out and then back in (herrings law) to achieve bsv

58
Q

what happens in prism fusion range when measuring convergent amplitudes (base-out)

A
  • continued innervation present when prism is removed (px still has active, tonic convergence as they don’t recover immediately after the prism base out removal)
  • reduces divergent amplitude if measured directly afterwards (but it isn’t truly reduced though, only for that time)
59
Q

in which order do you measure the prism fusion range

A
  • base-out
  • base-up right eye
  • base-in
  • base-down right eye
    in this order
    repeat for near using suitable target
60
Q

what happens when some patients do not report diplopia when testing prism fusion range

A
  • they will either suppress image of deviated eye or don’t appreciate/notice the diplopia (which can be overcome by placing red filter infant of eye which allows them to notice the diplopia)
61
Q

at which distance can prism fusion range diplopia be determined objectively at

A

near

62
Q

what should be done when a px cannot notice diplopia during prism fusion range test

A

place red filter infant of eye

63
Q

what happens to the eyes when a patient cannot take the prism which is placed infant of them during measuring prism fusion range

A

eyes will make a version movement instead
so this is the objective point of break point
and if px doesn’t notice diplopia, or doesn’t tell us, place a red filter infant of eye to help them notice

64
Q

list the steps of how to measure vertical fusion range

A
  • direct patient to a 6/60 letter
  • place prism bar in front of one eye, prism base down
    record this prism power at just before the break point
  • repeat with either
    prism base down in front of other eye
    or
    prism base up in front of same eye
  • repeat with a suitable letter target at patient’s preferred near working distance
65
Q

list the prism fusion ranges and corresponding break points

A
  • distance base-in = 5 - 10 (10)
  • distance base-out = 15 - 20 (20)
  • near base-in = 15 - 20 (20)
  • near base out = 35 - 40 (40)
66
Q

at which distance is prism fusion range greater at in comparison with at horizontal

A

greater at near than at distance

67
Q

at what vergence is prism fusion range better at

A

better at converging that diverging

68
Q

which base direction is greater in prism fusion range

A

base out is larger than base in

69
Q

which factors causes variances in prism fusion range

A
  • alertness

- toxicity

70
Q

what is our poorest fusion range

A

our ability to diverge at distance

71
Q

what is our best fusion range

A

ability to converge at near

72
Q

what is exophoria

A

tendency for the eye to move out

73
Q

what do you want to investigate on an exophoria px

A

how well they can control the tendency of the eyes to converge

74
Q

what do you want to investigate on an exophoria px at near

A

interested at base out fusion range

75
Q

what is the vertical prism fusion range distance and near

A

3 prism base up and down

76
Q

what is the torsional fusion range

A

between 8 - 22 prism dioptres

77
Q

what is the analysis of prism fusion range compared with

A

normals

78
Q

what does percival state

A

that convergent and divergent fusional reserves should be balanced
one should be no less than half of the other

79
Q

which prism fusion range and at which distance does the percival not work for

A

distance as distant base in = 5-10 (5 = 1/2 of 10)

and does take into account latent deviation

80
Q

what does sheard state

A

opposing fusional reserve to blur point should be twice degree of phoria
e.g. if 10 dioptre exophoria, you need 20 dioptres of base out convergent prism fusion range to cope

81
Q

what may insufficient fusional reserves result in

A
  • motor fusion breaking down
  • diplopia
  • asthenopic symptoms
82
Q

fusional amplitudes should be in..

A
  • normal range

- related to heterophoric position for the distance at which the vergences are measured

83
Q

give an example of fusional amplitudes, of 10 dioptre exophoria at distance

A

fusional reserves 14 prism base out and 14 prism base in

  • but as 10 prism base in required to correct heterophoria fusional reserves beyond heterophoric position are 4 prism base in and 24 prism base out fusion range
  • this suggests that reduced base out (convergent fusional reserves) are adequate to control deviation
84
Q

what type of device is a synoptophore

A

a haploscopic device

85
Q

how does the synoptophore work

A
  • each eye looks through a tube and a mirror on each eye piece reflect the image on the slide into the eye
  • eyepiece lenses are +6.50DS and targets mounted at focal length
  • 3.00DS inserted to simulate near viewing conditions
86
Q

in the synoptophore, which power lens in inserted to simulate near viewing conditions

A

-3.00DS

87
Q

what does the synoptophore estimate

A

prism fusion range of an individual

88
Q

how must each image be in comparison to one another in a synoptophore in order to measure fusion range

A

similar

89
Q

in a synoptophore, which different size slides are used subtending angles of

A
  • 1 degrees at nodal point
  • 3 degrees at nodal point
  • > 5 degrees at nodal point
90
Q

which size targets should be used comparable with visual acuity in a synoptophore

A

smallest targets, e.g. high va’s should use small target

91
Q

which size slides are better used for exotropias in a synoptophore

A

larger

92
Q

why are larger size slides better used for exotropias in a synoptophore

A

they are more likely to suppress

93
Q

in a synoptophore if in one eyepiece is a lion and the other is a cage, what will ox see if they can fuse the images

A

lion behind a cage

94
Q

which type of patients is a 20 prism base out test used on

A
  • children

- adults unable to co-operate with prism fusion range

95
Q

what is the 20 prism dioptre test assessed with

A

single base out prism placed before one eye and then the other

96
Q

what is child attention attracted by in a 20 dioptre prism test

A

near object e.g. toy at 33cm

97
Q

how much you work during the 20 dioptre prism test

A

quickly

98
Q

what is the 20 dioptre prism test useful in proving the presence of binocular single vision in

A
  • suspected pseudo strabismus

- child with poor fixation in which results on cover test are inconclusive

99
Q

what must you encourage a px to do if a 20 prism base out prism in not overcome

A

encourage to fuse images

100
Q

what is important to note from the 20 prism base out test

A
  • recovery movement as prism is removed
  • speed
  • accuracy
101
Q

what happens to the eyes in a 20 dioptre base out prism test which produces a normal response

A

eye under the prism moves in so the other eye moves out then in (herrings law) to take fixation
record as 20 dioptre base out overcome

102
Q

what happens to the eyes in a 20 dioptre base out prism test with the right eye suppressed

A

base out prism placed infant of left eye, both eyes make a version movement which in theory should give diplopia, but because they’re suppressing information from the right eye, the brain is no longer aware that the image is not on the fovea so the right eye doesn’t come back in

103
Q

what happens when the 20 dioptre base out prism is over the suppressing eye

A

no movement at all

104
Q

what is the 4 dioptre prism base out test for

A

macula suppression used when microtropia (small angle manifest strabismus) is suspected

105
Q

what happens during a 4 dioptre prism base out test

A
  • px is directed to an appropriate letter target at distance or near
  • prism is placed before right eye, image displaced outside macula area
    both eyes make versional movement towards apex of prism to left
    left eye then converges (which is more difficult to see with 4 dioptre prism base out as it is much smaller than 20) to re-establish foveal fixation
106
Q

what do microtropia patients develop in order to avoid diplopia

A

ARC

107
Q

a microtropia patient is…

A

rewired so that they think the deviating eye is looking straight ahead, and has a small area of central suppression which helps them look ahead

Binocular vision (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions