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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
the Viet-Mueller circle is formed by drawing:
a circle through the fixation point and the entrance pupil of each eye
26
uncrossed disparity is imaged on the _____ retina
nasal
27
crossed disparity is imaged on the ____ retina
temporal
28
what is the difference in visual direction between the two eyes that occurs when non-corresponding points are stimulated
binocular disparity
29
horizontal disparity gives rise to:
stereopsis, or the perception of depth
30
does vertical disparity give rise to depth perception?
no
31
points seen nearer than the fixation point within the Vieth Mueller circle are from _____ disparity
crossed
32
points seen farther than the fixation point are from _____ disparity
uncrossed
33
what does Panum's area allow for?
small disparities to give rise to depth perception within and single vision within a certain range
34
what occurs when images are outside of Panum;s areas and are on non-corresponding points
physiological diplopia | crossed and uncrossed
35
what occurs when the fixated target is diplopic (occurs with strabismus with little or no suppression)
pathological diplopia
36
binocular confusion occurs when
two different objects are seen in one direction or location
37
the geometric or theoretical horopter is called the
Vieth Mueller circle
38
horopter criterion: | when two targets (one presented to each eye) are perceived as lying on the same visual direction
identical visual direction horopter | superimposing
39
horopter criterion: | the locations perceived as lying the same distance from the subject as the fixation point, and the easiest to measure
apparent frontoparallel plane horopter
40
horopter criterion: | this takes advantage of Panum's area
singleness | objects within Panum's area seen as single
41
horopter criterion: | the region where you have maximum stereoacuity
minimum stereo acuity threshold
42
horopter criterion: | points in space seen as equidistant will not stimulate motor fusion
zero vergence
43
what does the term R stand for?
the ratio of the tangents of the two external longitudinal angles at any point on the horopter
44
R=
(tan a2) / (tan a1)
45
what is the R value for points on the V-M circle
R=1 for all ponts on the V-M circle
46
if R > 1, what is the relationship of a1 and a2?
a2 > a1
47
if R < 1, what is the relationship of a1 and a2?
a1 > a2
48
when is R > 1 ?
- inside on L field | - outside of R field
49
when is R < 1 ?
- outside of L field | - inside of R field
50
equation for R= | when converting spatial plot into analytical plot
R= H (tan a2) + R0
51
R0=
the relative magnification at the fixation point of the two eyes and results in a tilting of the horopter
52
what does H stand for?
the hering-hillebrand horopter deviation
53
what does the H value (the hering-hillebrand horopter deviation) measure?
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
changing H will change_____ and not change _____
changing slope-changes curvature/shape | does not change tilt
55
changing R0 (y-intercept) will change ____ and not change ____
change y-intercept (creating tilt) | not changing shape
56
magnifying in the horizontal meridian or axis 90 is what effect?
geometric effect
57
what does the magnifying lens in the geometric effect do?
-creates disparities in the horizontal plane in the eye with the magnifying lens (distorts space)
58
what would the patient perceive in the geometric affect with the axis 90 magnifying lens?
-patient would perceive the plane rotated away from the eye with the magnifying lens
59
magnifying in the vertical median or axis 180 is what effect?
induced effect
60
what are the unique features of vertical disparity?
- should not yield perception of depth | - small amounts lead to diplopia (due to limitation in vertical eye movements)
61
how can the axis 180 lens produce tilt?
produces tilt as if an axis 90 lens was introduced to the other eye (opposite distortion, rotation perceived)
62
when does the induced effect break down?
5-7% of magnification
63
the strengths of the induced and geometric effects are close to equal up to what point?
2% of magnification
64
effect of uniform magnification on the horopter
uniform mag of small amounts has little or no effect on the horopter
65
a magnification at 45 or 135 degrees produces:
a rotation around the horizontal axis
66
how does oblique magnification inclination or declination effect work?
results from a disparity gradient that creates the magnification effect
67
what factor changes H value?
prims | change curvature in space
68
how do prisms change H value?
- create a curve in space perception due to asymmetrical magnification - base creates a curve towards the patient - shift images towards apex
69
what does BO prism do to the analytical plot?
increases slope
70
how does BI prism affect the slope of the analytical plot?
less slope than with no lens
71
how does fixation distance affect H values?
the value of H stays constant
72
how does the horopter shape change with fixation distance?
- horopter shape changes (even tho H value is constant) | - VM circle also changing shape
73
the value of H is usually
+0.1 or +0.2
74
deviation of H value usually due to
can be attributed to a relative magnification in the retina
75
H and effects of nasal packing
local signs in the nasal retina are spaced closer together (called nasal packing) -nasal retina tends to minify temporal space
76
when the angle on the nasal retina is larger than the corresponding temporal angle on the other eye, then H is __
positive +
77
the nasal to temporal asymmetry demonstrated in monocular partition experiments is called
``` Kundt asymmetry (most people have this one) ```
78
asymmetry where temporal retina (or nasal field) is overestimated is the
Munsterberg deviation
79
describe the vertical horopter location
tilted away from the individual
80
basic problem in strabismus is
the two oculocentric directions are pointing in different points in space
81
where is the "zero point"?
where the fixated target stimulates the retina in the turned eye
82
how can someone compensate for the strabismus?
suppression or changing correspondence pattern
83
objective angle of deviation=
H | cover test, prism
84
subjective angle of directionalization=
S | when does it line up, phorias
85
angle of anomaly (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
how do you measure correspondence directly?
after-image test - horizontal after-image presented to fixating eye - vertical after-image presented to deviated eye
87
how do you calculate angle of animal from the subjective and objective angles?
A = H (objective) - S (subjective) eso is - exo is +
88
a condition in which the two foveal and other homologous retinal loci do not correspond to each other in regard to visual direction
anomalous correspondance (AC) in strabismus
89
type of correspondence: | when the objective and subjective angles are equal and the angle of anomaly is zero
normal correspondance
90
type of correspondence: | when the angle of anomaly and the objective angle are equal
harmonious anomalous correspondence
91
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
unharmonious anomalous correspondence
92
sensory theory for AC
- adaptation to the sensory issues resulting from abnormal eye alignment - deals with confusion and diplopia - problem explaining co-variation
93
motor theory for AC
- innervational pattern to the EOMs dictates the correspondence pattern - explains co-variation
94
difference between registered and non-registered eye movements in the motor theory for AC
registered: saccadic, cancels out | non-registered: vergence (in normal system), they don't need to be registered
95
abnormal disparity detectors theory for AC
-AC has a variable detection system which changes in sync with disparity convergence (esotropia) or disparity divergence (exotropia)
96
what evidence supports the abnormal disparity detectors theory for AC
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
differences about measuring the horopter in strabismus
- difficult to measure, especially IVD - more variable in AC than NC, especially for the singleness horopter - horopters are excessively curved
98
intermittent exotropes may exhibit a horopter that is:
excessively curved
99
esotropes with NC may exhibit an
excessively curved horopter
100
esotropes with AC may show:
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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