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Vision Science 5 > Lecture 4 > Flashcards

Lecture 4 Flashcards

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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
When is there better sensitivity regarding CFF?
when stimuli are in phase
26
low temporal frequency (ex: 5 Hz) will result in what?
facilitation
27
middle temporal frequency results in what?
complete summation
28
high temporal frequency results in what?
partial summation
29
how do you convert cycles/degree to snellen?
*idk
30
what is 30 c/deg in snellen?
20/20
31
For high spatial frequency cutoff what does it correspond to?
VA
32
Similar retinal luminance results in what?
Binocular perception slightly brighter than monocular
33
How do we measure small interocular luminance differences?
average two eyes luminance
34
Large interocular luminance difference leads to what?
suppression of the dimmer eye
35
clinical situation for larger interocular luminance in one eye
cataract or end stage glaucoma in one eye
36
Fechner’s Paradox and Brightness Averaging
• 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
Large Interocular Difference Leads to what?
suppression
38
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.
Aftereffect: visual illusion
39
Aftereffect manifests through what 3 things?
motion tilt size
40
interocular transfer of tilt aftereffect results
* After effect not as strong as viewing with one eye | * Evidence for neurons receiving binocular input
41
Patient with disrupted binocularity, such as strabismus, does not have what?
interocular transfer
42
When binocular summation is a disadvantage
In some persons, flashing/flickering lights can trigger an epileptic attack, but closing one eye can mitigate this effect. (CFF lower monocularly).
43
images with similar features fall on corresponding points or within Panum’s area Result in binocular summation
binocular fusion
44
dissimilar images falls on corresponding points
binocular suppression or rivalry
45
“The failure of one of the two monocular visual systems to perceive a normally visible object in all or part of the visual field.”
Binocular Suppression
46
entire image from one retina being suppressed.
gross suppression
47
fovea in one eye being suppressed.
central suppression
48
when is there physiological suppression that is unilateral? (if different image qualities)
- Monovision - Significant uncorrected anisometropia Monocular - macular pathology
49
when is physiological suppression alternating? (if similar image qualities)
binocular rivalry
50
One eye is corrected for distance and one for near. Success occurs when the patient only sees the focused image (“blur suppression”).
Physiological Suppression in Monovision
51
what type of physiological suppression is in monovision?
gross suppression
52
Monovision works best with what?
low add powers or early presbyopes
53
• 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
physiological suppression
54
Pathological suppression is suppression induce by what?
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
Response to prolonged diplopia, only found in what?
early onset strabismus
56
Normal viewing environment stimulates what?
suppression more strongly than clinical testing condition. | • Worth 4 dot underestimate suppression
57
Worth 4 Dot Underestimate Suppression
 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
Pathological suppression scotoma in strabismus:
not absolute scotoma
59
Patient can have peripheral fusion outside of
the scotoma area
60
Exotropia usually show
more extensive suppression (entire temporal hemiretina)
61
Size of scotoma correlates to the size of the angle of deviation
esotropia
62
Scotoma Size and the Distance of W4D test
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
-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
binocular rivalry
64
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?
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
T/F: monocular tilt after effect is a phenomenon that supports binocular neuronal summation theory (interaction theory)
false
66
pt sees 3 green dots in worth 4 dot test. | how do we record the result?
OD suppression
67
Provide cues for relative distance of the two objects
Da Vinci Stereopsis
68
a special form of rivalry
binocular luster

Vision Science 5 (6 decks)

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