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Vision Science 5 > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

better performance of visual functions with two eyes than monocular performance; benefit of having 2 eyes

A

binocular summation

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2
Q

Possible types of binocular summation:

A 
 Facilitation
 Complete summation
 Partial summation
 No summation
 Inhibition
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3
Q

Where does normal binocular observer fall in types of binocular summation?

A

partial summation

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4
Q

Both > L + R

A

Facilitation

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5
Q

Both= L + R

A

Complete Summation

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6
Q

Both < L + R, but > L or R

A

partial summation

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7
Q

Both=L or Both= R

A

No Summation

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8
Q

Both < L or Both < R

A

Inhibition

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9
Q

– Simply by adding one more detector, you have 40% better chance of detecting a stimulus than one detector (explained by statistics)
– No interaction between eye

A

• Probability summation

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10
Q

– When stimuli are synchronous in space and time, binocular vision is stimulated
– Much better chance of detection than predicted by statistics

A

• Neuronal summation

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11
Q

how sensitive we are to flickering light (temporal testing)

A

critical flicker fusion frequency (CFF)

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12
Q

out of phase result for binocular percept with summation

A

cancelled out

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13
Q

monocular cff

A

49.8

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14
Q

binocular cff

A
  1. something
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15
Q

how do we combine info from 2 eyes?

A
  • probability summation

- neuronal summation

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16
Q

Some Visual Functions Showing Binocular Summation

A

 Threshold light detection
 CFF (Critical Flicker Fusion Frequency): goes up
 Contrast threshold: goes down (better contrast sensitivity)
 Resolution threshold : goes down (better VA)
 Brightness
 Interocular transfer

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17
Q

CSF for high spatial frequency corresponds to what clinical test result?

A

VA

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18
Q

Monocular CSF at high spatial frequency

A

we are more sensitive to different contrasts

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19
Q

improvement of binocular compared to monocular for CSF in high and low sf

A

40% improvement uniformly

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20
Q

With monocular blur, the binocular contrast sensitivity declines with what?

A

increasing blur

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21
Q

WHAT HAPPENS with significan monocular blur?

A

inhibition

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22
Q

When more than +1.50 D to +2.00 D blur, binocular sensitivity is worse than what?

A

monocular

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23
Q

Why are some patients fit with monovision unable to accept more than a 1.50- 2.00 diopters difference in focus between the two eyes?

A

one eye is so blurred, that it makes them uncomfortable.

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24
Q

why is binocular cff improvement so small compared to monocular cff?

A

we are testing one point. we are trying to find threshold at one point.

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25
Q

When is there better sensitivity regarding CFF?

A

when stimuli are in phase

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26
Q

low temporal frequency (ex: 5 Hz) will result in what?

A

facilitation

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27
Q

middle temporal frequency results in what?

A

complete summation

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28
Q

high temporal frequency results in what?

A

partial summation

29
Q

how do you convert cycles/degree to snellen?

30
Q

what is 30 c/deg in snellen?

31
Q

For high spatial frequency cutoff what does it correspond to?

32
Q

Similar retinal luminance results in what?

A

Binocular perception slightly brighter than monocular

33
Q

How do we measure small interocular luminance differences?

A

average two eyes luminance

34
Q

Large interocular luminance difference leads to what?

A

suppression of the dimmer eye

35
Q

clinical situation for larger interocular luminance in one eye

A

cataract or end stage glaucoma in one eye

36
Q

Fechner’s Paradox and Brightness Averaging

A

• Brightness averaging does not apply when interocular luminance difference is too Large.
Suppress the dimmer eye
• Similar effect by significant monocular retinal blur
+10.00 D lens in front of one eye

37
Q

Large Interocular Difference Leads to what?

A

suppression

38
Q

Fatiguing a specifically tuned visual neurons, such as specific orientation detector neurons, the perception of a subsequently viewed target will be biased toward the opposite direction.

A

Aftereffect: visual illusion

39
Q

Aftereffect manifests through what 3 things?

A

motion
tilt
size

40
Q

interocular transfer of tilt aftereffect results

A
  • After effect not as strong as viewing with one eye

* Evidence for neurons receiving binocular input

41
Q

Patient with disrupted binocularity, such as strabismus, does not have what?

A

interocular transfer

42
Q

When binocular summation is a disadvantage

A

In some persons, flashing/flickering lights can trigger an epileptic attack, but closing one eye can mitigate this effect. (CFF lower monocularly).

43
Q

images with similar features fall on corresponding points or within Panum’s area
Result in binocular summation

A

binocular fusion

44
Q

dissimilar images falls on corresponding points

A

binocular suppression or rivalry

45
Q

“The failure of one of the two monocular visual systems to perceive a normally visible object in all or part of the visual field.”

A

Binocular Suppression

46
Q

entire image from one retina being suppressed.

A

gross suppression

47
Q

fovea in one eye being suppressed.

A

central suppression

48
Q

when is there physiological suppression that is unilateral? (if different image qualities)

A
  • Monovision
  • Significant uncorrected anisometropia Monocular
  • macular pathology
49
Q

when is physiological suppression alternating? (if similar image qualities)

A

binocular rivalry

50
Q

One eye is corrected for distance and one for near. Success occurs when the patient only sees the focused image (“blur suppression”).

A

Physiological Suppression in Monovision

51
Q

what type of physiological suppression is in monovision?

A

gross suppression

52
Q

Monovision works best with what?

A

low add powers or early presbyopes

53
Q

• Two eyes are equal in their contribution to the binocular visual system (one eye is not very dormant over the other)
• The eye presented with the weaker (less salient) image will be suppressed.
– Dimmer, lower contrast, blurred, in retinal periphery

A

physiological suppression

54
Q

Pathological suppression is suppression induce by what?

A

stimulus conditions which cause fusion in normals.
• Similar images on corresponding points strongly induce pathological suppression in strabs.
• The turned eye will be suppressed

55
Q

Response to prolonged diplopia, only found in what?

A

early onset strabismus

56
Q

Normal viewing environment stimulates what?

A

suppression more strongly than clinical testing condition.

• Worth 4 dot underestimate suppression

57
Q

Worth 4 Dot Underestimate Suppression

A

 Darkness weakens suppression
– Use neutral density filter to measure the
“depth” of suppression.
 Absence of a textured background weakens suppression
 Red green glasses weakens suppression while promoting rivalry
– Used in therapy for anti-suppression.

58
Q

Pathological suppression scotoma in strabismus:

A

not absolute scotoma

59
Q

Patient can have peripheral fusion outside of

A

the scotoma area

60
Q

Exotropia usually show

A

more extensive suppression (entire temporal hemiretina)

61
Q

Size of scotoma correlates to the size of the angle of deviation

62
Q

Scotoma Size and the Distance of W4D test

A

For patient with small angle ET (microtropia), the scotoma size can be small enough to be just around fovea.
For near W4D test (normal testing distance is 40cm), the suppression of scotoma might be missed because the angular subtence of stimulus is larger than the scotoma size.
“Walk-away” test method used in diagnosing monofixation syndrome (microtropia)

63
Q

-Vision which alternates between the eyes in part or all of visual space.

• Intermittent and alternating suppression of brightness, color, and/or contour
• Occurs when very different images of equal salience fall on corresponding points
– Similar in spatial frequency or contrast

A

binocular rivalry

64
Q

To confirm monofixation syndrome, in pt with 20/30 OD and 20/20 OS, with 6 PD constant RET at distant and near. Test is 4 BO prism in front of right eye. What type of eye movements will u see?

A

Both od and os show no movement; small angles will make a suppression scotoma in right eye. image still falls within suppression scotoma area. left eye does not move because its a conjugated movement.

65
Q

T/F: monocular tilt after effect is a phenomenon that supports binocular neuronal summation theory (interaction theory)

66
Q

pt sees 3 green dots in worth 4 dot test.

how do we record the result?

A

OD suppression

67
Q

Provide cues for relative distance of the two objects

A

Da Vinci Stereopsis

68
Q

a special form of rivalry

A

binocular luster

Vision Science 5 (6 decks)

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