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Vision Science 5 > Lecture 3 > Flashcards

Lecture 3 Flashcards

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1
Q

All points along the circumference of the VMO stimulates what?

A

corresponding points

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2
Q

All objects located on VMO stimulate what?

A

0 binocular disparity

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3
Q

The horopter is approximately ________ in near vision

A

bow-shaped

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4
Q

The 3 assumption for VMO

A

Both retinas are spherical.
Both retinas have symmetric distribution of local signs across nasal and temporal retinas.
Right and left retina are the same size with the same local sign geometry.

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5
Q

When we actually do an experiment on a human, we find that the locations in space that have identical monocular visual directions are what?

A

imaged onto corresponding points, are not the same as the Vieth-Müller Circle.

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6
Q

The empirical longitudinal horopter is generally ______________ than the VMO.

A

less concave

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7
Q

Methods of Measuring ELH

Horopter criteria:

A

1) Identical visual direction
2) Equidistance (Stereoscopic depth matching)
3) Singleness (haplopia)
4) Minimum stereoscopic threshold
5) Zero vergence

*first 2 are more commonly used methods

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8
Q

When 2 targets, each presents to one eye, are perceived as lying in a single visual direction, the images of those targets must be formed on what?

A

corresponding points

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9
Q

What is the only true horopter criterion (most accurate) and why?

A

Identical visual direction because it’s the only one that directly measures the visual direction.

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10
Q

Nonius Horopter is aka

A

identical visual direction

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11
Q

Equidistance Horopter is aka

A

steroscopic depth matching or apparent frontoparallel plane (AFPP) method

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12
Q

Advantage of equidistance horopter

A

examiner can actually see the shape of the horopter directly

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13
Q

disadvantage of equidistance horopter

A

AFPP method does not reflect the effects of fixation disparity, unlike the Identical visual direction

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14
Q

fixation disparity

A

most people have an error so our eyes look either ahead or behind the actual target; only observed with nonius horopter

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15
Q

The most popular way to measure horopter

A

Howard—Dolman Apparatus

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16
Q

The Singleness (haplopia) horopter actually measures what?

A

the extent of Panum’s area at the fovea and at eccentric locations.

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17
Q

The width of the zone of singleness reflects what?

A

PANUMS SPACE

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18
Q

What is the most commonly used horopter?

A

equidistance

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19
Q

Horopter is a collection of points which have what?

A

the exact same visual direction on each eye

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20
Q

What is the most accurate horopter?

A

identical visual direction

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21
Q

Why is the empirical longitudinal horopter different from the theoretical horopter?

A

all of the above? go back to check

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22
Q

Two variables that affect the shape of the ELH

A

Skew (Relative magnification, R)

Curvature (Hering-Hillerbrand deviation, H)

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23
Q

Regarding skew, “External” referring to being outside of the eye because?

A

we can not directly measure these angles.

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24
Q

The inferred angle is influenced by

A

the optics of the eye.

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25
Q

What is R?

A

the relative magnification of the retinal images between the two eyes.

26
Q

When target on the horopter,

α1=α2, R=1, will have what magnification?

A

no relative magnification

27
Q

When one eye image is magnified or minified relative to the other eye, as in aniseikonia
α1≠α2, R ≠ 1, what happens to the target?

A

target no longer falls on the horopter

28
Q

How do we make α1=α2 again?

A

observer has to move the target

29
Q

review relative magnification slides

A

boo

30
Q

The horopter is skewed toward which eye?

A

magnified eye

31
Q

The perception of frontal plane is mirror image of what?

A

horopter

32
Q

The difference in curvature between the horopter and
Hering- the VMO, as
Hillerbrand deviation
measured at the fixation point, is called

A

Hering-Hillerbrand deviation (H)

33
Q

The value of H typically ranges from what?

A

+0.1 to +0.2

34
Q

Does H indicate a flatter or steeper horopter than VMO?

A

flatter

35
Q

Why H>0 usually? Why ELH is flatter than VMO?

A

Both retinas are spherical.
Both retinas have symmetric distribution of local signs across nasal and temporal retinas.
—“Nasal packing” phenomenon: local sign in nasal retina are spaced closer together
—Temporal visual space is overestimated
Right and left retina are the same size with the same local sign geometry.

36
Q

Which visual space is overestimated?

A

temporal visual space

37
Q

What happens to the shape of horopter when we increase fixation distance?

A

curvature changes so that it goes from covex to flat than concave

*however, the changes in curvature of the horopter mirror changes in curvature of the VM circle, yielding no net change in the value of H

38
Q

the viewing distance at which the apparent and objective frontal plane coincide

A

Abathic distance

39
Q

When is the horopter truly flat?

A

abathic distance

40
Q

What is the abathic distance

A

6 meters

41
Q

fixation disparity

A

misalignment of the visual axes

42
Q

binocular disparity

A

non-correspondence of the retinal regions stimulated by a target located off the horopter

43
Q

Two eyes slightly under- converge, fixation point behind the target

A

Exo Fixation Disparity

44
Q

Two eyes slightly over- converge, fixation point in front of the target

A

Eso Fixation Disparity

45
Q

a small purposeful error in vergence.

A

fixation disparity

46
Q

Factors affecting offset of ELH

A

fixation disparity

strabismus

47
Q

Strabismus affecting ELH

A

– Horopter shifts toward the intersection of the
visual axis
– Abnormal, seen in some strabismus – Sensory fusion is disrupted

48
Q

Fixation Disparity regarding ELH

A

normal, does not disrupt sensory fusion

49
Q

aniseikonia and horopter

A

Geometric effect
Induced effect
size lens

50
Q

geometric effect

A

magnification along horizontal meridian

51
Q

two eyes image size are different from each other

A

aniseikonia

52
Q

magnification along vertical meridian

A

induced effect

53
Q

special lens that only change the image size with no optical effect
Meridional size lens: only change the size alone one meridion.

A

size lens

54
Q

When an axis 90 meridional magnifier is placed in front of right eye, where is the image magnified?

A

horizontally, producing retinal disparities that yield a percept of the world tilting AWAY from the right eye

55
Q

Induced effect can be measured by what?

A

the AFPP horopter apparatus (Howard-Dolman)

56
Q

Nonius horopter will not rotate because what?

A

no physical horizontal binocular disparity being created.

57
Q

what causes nonuniform magnification?

A

Prisms

*More magnification at the apex than at the base

58
Q

BI prisms in front of both eyes:

A

 Temporal side more magnified than the nasal side
 Horopter bends toward observer at the temporal side
 Perceived world is a mirror image of the horopter
 Perceived world bends away from observer

59
Q

T/F: EHL is more curved than the VMO

A

true

*when H is less than 0

60
Q

Clinical situations of curvature change where H < 0

A
  • Divergence excess

* Intermittent esotropia

61
Q

3 clinical situations for irregular horopter

A

-

62
Q

Regional spatial distortion, may be a result of

anomalous retinal correspondence

A

Flom Notch

Vision Science 5 (6 decks)

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