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Binocular Vision > MT1 > Flashcards

MT1 Flashcards

1
Q

type of aniseikonia that is caused by a difference in retinal image size between the two eyes and is seen in patients with aniseometropia

A

optical aniseikonia

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2
Q

type of aniseikonia that is a retinal image size difference caused by a spacial lens such as an focal magnifier or size lens

A

induced aniseikonia

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3
Q

type of aniseikonia that is due to stretching or contracting of the retina

A

retinal aniseikonia

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4
Q

type of aniseikonia that is a small non-optical aniseikonia that occurs when the image should be optically equal but are perceived as different

A

neural or essential aniseikonia

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5
Q

types of things that can cause retinal aniseikonia

A
  • retinal detachment
  • retinoschisis
  • macular hole
  • macular edema
  • epiretinal membrane
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6
Q

every diopter of anisometropia can cause ___ % of aniseikonia

A

1-2 %

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7
Q

aniseikonia above __ % can disrupt binocular fusion and stereopsis

A

7 %

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8
Q

type of aniseikonia test that is the best test, no longer available, uses septum to divide targets, and uses 5 vertical lines and a cross

A

space eikonometer

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9
Q

type of aniseikonia test that is a direct comparison test that is a book that can be rotated to measure different meridians and uses red-green glasses to dissociate

A

new aniseikonia test (NAT)

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10
Q

type of aniseikonia test that is a direct comparison test, computerized, and a little better than the NAT test

A

aniseikonia inspector (AI)

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11
Q

how does the NAT test compare to the space eikonometer ?

A

NAT underestimated the amount of aniseikonia when compared to space eikonometer in both meridians

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12
Q

what is the most reasonable factor and logical explanation for the inaccuracy of the NAT

A

sensory fusional response that rescales the image (red-green target), swimming around feeling in red-green glasses makes it hard to judge differences

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13
Q

how does the AI test compare to the space eikonometer ?

A

AI showed an underestimation that was greater in the horizontal meridian

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14
Q

AI agreement values between the testing sessions are:

A

95% confidence intervals to be +/- 2.0%

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15
Q

what occurs when the principle visual direction is different from the fovea

A

eccentric fixation (EF)

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16
Q

what is the principle visual direction in eccentric fixation?

A

an off-foveal point

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17
Q

what condition is common in patients with strabismic amblyopia?

A

eccentric fixation (EF)

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18
Q

when a patient uses a point other than the fovea when looking straight ahead is called:

A

eccentric viewing

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19
Q

does the principle visual direction change in eccentric viewing?

A

no

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20
Q

eccentric viewing is common in what condition?

A

macular degeneration

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21
Q

describe the law of identical visual direction

A

objects lying in the same visual direction in each eye will be seen as lying in a single visual direction under binocular viewing conditions
-the fovea indicate the same principle viewing direction

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22
Q

what is egocentric localization?

A

objects striking each fovea are perceived to fall on a single point midway between the two eyes
-this has been called the cyclopean eye

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23
Q

what can influence the position of egocentric localization?

A

eye dominance

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24
Q

“a geometric representation of the corresponding points in each eye”

A

Vieth-Mueller Circle

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25
Q

the Viet-Mueller circle is formed by drawing:

A

a circle through the fixation point and the entrance pupil of each eye

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26
Q

uncrossed disparity is imaged on the _____ retina

A

nasal

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27
Q

crossed disparity is imaged on the ____ retina

A

temporal

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28
Q

what is the difference in visual direction between the two eyes that occurs when non-corresponding points are stimulated

A

binocular disparity

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29
Q

horizontal disparity gives rise to:

A

stereopsis, or the perception of depth

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30
Q

does vertical disparity give rise to depth perception?

A

no

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31
Q

points seen nearer than the fixation point within the Vieth Mueller circle are from _____ disparity

A

crossed

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32
Q

points seen farther than the fixation point are from _____ disparity

A

uncrossed

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33
Q

what does Panum’s area allow for?

A

small disparities to give rise to depth perception within and single vision within a certain range

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34
Q

what occurs when images are outside of Panum;s areas and are on non-corresponding points

A

physiological diplopia

crossed and uncrossed

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35
Q

what occurs when the fixated target is diplopic (occurs with strabismus with little or no suppression)

A

pathological diplopia

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36
Q

binocular confusion occurs when

A

two different objects are seen in one direction or location

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37
Q

the geometric or theoretical horopter is called the

A

Vieth Mueller circle

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38
Q

horopter criterion:

when two targets (one presented to each eye) are perceived as lying on the same visual direction

A

identical visual direction horopter

superimposing

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39
Q

horopter criterion:

the locations perceived as lying the same distance from the subject as the fixation point, and the easiest to measure

A

apparent frontoparallel plane horopter

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40
Q

horopter criterion:

this takes advantage of Panum’s area

A

singleness

objects within Panum’s area seen as single

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41
Q

horopter criterion:

the region where you have maximum stereoacuity

A

minimum stereo acuity threshold

42
Q

horopter criterion:

points in space seen as equidistant will not stimulate motor fusion

A

zero vergence

43
Q

what does the term R stand for?

A

the ratio of the tangents of the two external longitudinal angles at any point on the horopter

44
Q

R=

A

(tan a2) / (tan a1)

45
Q

what is the R value for points on the V-M circle

A

R=1 for all ponts on the V-M circle

46
Q

if R > 1, what is the relationship of a1 and a2?

A

a2 > a1

47
Q

if R < 1, what is the relationship of a1 and a2?

A

a1 > a2

48
Q

when is R > 1 ?

A
  • inside on L field

- outside of R field

49
Q

when is R < 1 ?

A
  • outside of L field

- inside of R field

50
Q

equation for R=

when converting spatial plot into analytical plot

A

R= H (tan a2) + R0

51
Q

R0=

A

the relative magnification at the fixation point of the two eyes and results in a tilting of the horopter

52
Q

what does H stand for?

A

the hering-hillebrand horopter deviation

53
Q

what does the H value (the hering-hillebrand horopter deviation) measure?

A

difference in curvature between the VM circle and the horopter at a particular fixation point
(the corresponding points on the horopter are not evenly spaced)

54
Q

changing H will change_____ and not change _____

A

changing slope-changes curvature/shape

does not change tilt

55
Q

changing R0 (y-intercept) will change ____ and not change ____

A

change y-intercept (creating tilt)

not changing shape

56
Q

magnifying in the horizontal meridian or axis 90 is what effect?

A

geometric effect

57
Q

what does the magnifying lens in the geometric effect do?

A

-creates disparities in the horizontal plane in the eye with the magnifying lens (distorts space)

58
Q

what would the patient perceive in the geometric affect with the axis 90 magnifying lens?

A

-patient would perceive the plane rotated away from the eye with the magnifying lens

59
Q

magnifying in the vertical median or axis 180 is what effect?

A

induced effect

60
Q

what are the unique features of vertical disparity?

A
  • should not yield perception of depth

- small amounts lead to diplopia (due to limitation in vertical eye movements)

61
Q

how can the axis 180 lens produce tilt?

A

produces tilt as if an axis 90 lens was introduced to the other eye (opposite distortion, rotation perceived)

62
Q

when does the induced effect break down?

A

5-7% of magnification

63
Q

the strengths of the induced and geometric effects are close to equal up to what point?

A

2% of magnification

64
Q

effect of uniform magnification on the horopter

A

uniform mag of small amounts has little or no effect on the horopter

65
Q

a magnification at 45 or 135 degrees produces:

A

a rotation around the horizontal axis

66
Q

how does oblique magnification inclination or declination effect work?

A

results from a disparity gradient that creates the magnification effect

67
Q

what factor changes H value?

A

prims

change curvature in space

68
Q

how do prisms change H value?

A
  • create a curve in space perception due to asymmetrical magnification
  • base creates a curve towards the patient
  • shift images towards apex
69
Q

what does BO prism do to the analytical plot?

A

increases slope

70
Q

how does BI prism affect the slope of the analytical plot?

A

less slope than with no lens

71
Q

how does fixation distance affect H values?

A

the value of H stays constant

72
Q

how does the horopter shape change with fixation distance?

A
  • horopter shape changes (even tho H value is constant)

- VM circle also changing shape

73
Q

the value of H is usually

A

+0.1 or +0.2

74
Q

deviation of H value usually due to

A

can be attributed to a relative magnification in the retina

75
Q

H and effects of nasal packing

A

local signs in the nasal retina are spaced closer together (called nasal packing)
-nasal retina tends to minify temporal space

76
Q

when the angle on the nasal retina is larger than the corresponding temporal angle on the other eye, then H is __

A

positive +

77
Q

the nasal to temporal asymmetry demonstrated in monocular partition experiments is called

A 
Kundt asymmetry 
(most people have this one)
78
Q

asymmetry where temporal retina (or nasal field) is overestimated is the

A

Munsterberg deviation

79
Q

describe the vertical horopter location

A

tilted away from the individual

80
Q

basic problem in strabismus is

A

the two oculocentric directions are pointing in different points in space

81
Q

where is the “zero point”?

A

where the fixated target stimulates the retina in the turned eye

82
Q

how can someone compensate for the strabismus?

A

suppression or changing correspondence pattern

83
Q

objective angle of deviation=

A

H

cover test, prism

84
Q

subjective angle of directionalization=

A

S

when does it line up, phorias

85
Q

angle of anomaly (A)=

A

the angle subtended at the center rotation of the eye by the fovea and anomalous point a. A can be determined directly or indirectly

86
Q

how do you measure correspondence directly?

A

after-image test

  • horizontal after-image presented to fixating eye
  • vertical after-image presented to deviated eye
87
Q

how do you calculate angle of animal from the subjective and objective angles?

A

A = H (objective) - S (subjective)
eso is -
exo is +

88
Q

a condition in which the two foveal and other homologous retinal loci do not correspond to each other in regard to visual direction

A

anomalous correspondance (AC) in strabismus

89
Q

type of correspondence:

when the objective and subjective angles are equal and the angle of anomaly is zero

A

normal correspondance

90
Q

type of correspondence:

when the angle of anomaly and the objective angle are equal

A

harmonious anomalous correspondence

91
Q

type of correspondence:
when the objective angle is larger than the subjective angle, but the angle of anomaly is still less than the objective angle

A

unharmonious anomalous correspondence

92
Q

sensory theory for AC

A
  • adaptation to the sensory issues resulting from abnormal eye alignment
  • deals with confusion and diplopia
  • problem explaining co-variation
93
Q

motor theory for AC

A
  • innervational pattern to the EOMs dictates the correspondence pattern
  • explains co-variation
94
Q

difference between registered and non-registered eye movements in the motor theory for AC

A

registered: saccadic, cancels out

non-registered: vergence (in normal system), they don’t need to be registered

95
Q

abnormal disparity detectors theory for AC

A

-AC has a variable detection system which changes in sync with disparity convergence (esotropia) or disparity divergence (exotropia)

96
Q

what evidence supports the abnormal disparity detectors theory for AC

A

clinical finding that large vergence disparity movements are observed when prism that is correcting the strabismus angle is placed over the eyes
-the larger vergence movement re-establishes the amount of AC

97
Q

differences about measuring the horopter in strabismus

A
  • difficult to measure, especially IVD
  • more variable in AC than NC, especially for the singleness horopter
  • horopters are excessively curved
98
Q

intermittent exotropes may exhibit a horopter that is:

A

excessively curved

99
Q

esotropes with NC may exhibit an

A

excessively curved horopter

100
Q

esotropes with AC may show:

A

a horopter notch near the fixation point

-horopter usually b/w the fixation target and the angle of strabismus

Binocular Vision (1 decks)

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