4 - Fusion and Correspondence (Exam 1) Flashcards

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1
Q

What are the 3 possible scenarios that can cause single vision with two eyes?

A
  1. Perceptual merging of two images
  2. Monocular viewing
  3. Suppression (constant or alternating)
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2
Q

What is the alternation/ suppression theory?

A

The perception of single vision is never the merging or combination of both eyes images

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3
Q

What is the fusion theory?

A

The perception of single vision comes from the merging of each eye’s percept to form one unique percept.

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4
Q

What is allelotropia?

A

The perceptual representation of two disparate directions as one single unique visual direction.

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5
Q

What are the 2 types of fusion?

A
  1. Motor fusion

2. Sensory fusion

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6
Q

What is the perceptual characteristic of sensory fusion?

A

Allelotropia

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7
Q

What is sensory fusion?

A

Perceptual process where two similar targets are combined at the neural level without the need for motor fusion.

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8
Q

What is motor fusion?

A

The mechanical movement of both eyes that allows images to fall on the horopter or within Panum’s fusional space.

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9
Q

What is the goal of motor fusion?

A

To change eye position to allow sensory fusion to occur

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10
Q

What are 6 factors affecting sensory fusion?

A
  1. Target similarity
  2. Target simultaneity
  3. Retinal eccentricity
  4. Spatial frequency
  5. Temporal frequency
  6. Spatio-temporal modulation frequency
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11
Q

How does target similarity relate to sensory fusion?

A

Small differences in orientation can be fused

Fused images are averaged

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12
Q

What do large differences in orientation result in with regards to target similarity?

A

Rivalry -

Bi-stable piecemeal alternation between each eyes images

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13
Q

What is meant by target simultaneity?

A

If L and R images are presented at the same time, they are presented in perfect temporal synchrony
If one image is presented a short time after the other, temporal asynchrony is created

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14
Q

What is meant by retinal eccentricity?

A

Relative distance from the fovea

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15
Q

How does spatial frequency relate to sensory fusion?

A

Panum’s fusional area get smaller as spatial frequency increases, and becomes horizontally elliptical at higher that 2.5 cycles per degree

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16
Q

How does spatio-temporal modulation frequency relate to sensory fusion?

A

Subject experiences 3D corrugated wave only with horizontal disparity modulation
Panum’s fusional area becomes more circular as temporal frequency increases, horizontal has dramatic change.

17
Q

What is the equation for disparity gradient?

A

n/d

18
Q

With what value of disparity gradient will targets be able to fuse?

A

Disparity gradient less than 1

19
Q

With what value of disparity gradient will targets not be able to fuse?

A

Disparity gradient greater than 1

20
Q

What is a major characteristic of disparity gradient?

A

It creates a forbidden cone-like zone around every fused target in which adjacent targets will not be fused

21
Q

Do changes in CONTRAST and LUMINANCE affect the extent of Panum’s fusional area?

A

No

22
Q

Can stereoscopic depth be perceived for diplopic targets?

A

Yes

23
Q

What is fixation disparity?

A

The angular discrepancy between the point of convergence and the target of interest

24
Q

When are patients with fixation disparity able to perceive targets as single and fused?

A

When the magnitude of the fixation disparity does not exceed the limit of Panum’s fusional space

25
Q

What is the “normal” fixation disparity seen in patients?

A

Between 4 arc minutes of eso FD and 6 arc minutes of exo FD

26
Q

What type of fixation disparity do esophores usually have?

A

Eso fixation disparity

27
Q

What type of fixation disparity do exophores usually have?

A

Exo fixation disparity

28
Q

What could be a cause of an exophore that has an eso fixation disparity?

A

A past that involves vision therapy

29
Q

What 2 requirements must a fixation disparity measurement target fulfill?

A
  1. Binocular fusion lock
    target seen by both eyes
  2. Monocular targets
    target seen by one eye only
30
Q

What is the angular offset in arc minutes between monocular targets in a fixation disparity target?

A

The fixation disparity

31
Q

What is the amount of prism required to align monocular fixation targets?

A

Associated phoria

measure in prism diopters

32
Q

What are Worth’s 3 levels of fusion?

A
  1. 1st degree fusion
  2. 2nd degree fusion
  3. 3rd degree fusion
33
Q

What is 1st degree fusion?

A

Simultaneous perception of dissimilar monocular targets

Superimposition is where dissimilar targets are perceived in the same visual direction

34
Q

What is 2nd degree fusion?

A

Flat fusion

suppression checks in place

35
Q

What is 3rd degree fusion?

A

Stereopsis

two similar targets with slight differences in visual direction perceived to lie in depth