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NBEO Part 1 > Perception > Flashcards

Perception Flashcards

1
Q

Threshold

A

Minimum stimulus that an individual can detect 50% of the time

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2
Q

Threshold is _____ of sensitivity

A

inverse

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3
Q

Method of ascending limits

A

Increase brightness until it is detected. how dark adaption occurs

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4
Q

Method of descending limits

A

Decrease brightness until cannot see any longer. Snellen VA.

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5
Q

Method of constant stimuli

A

The experimental varies the intensity randomly. Take a long time to complete

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6
Q

Stair step Method

A

Gradually increase light until deleted and then decrease until not detected. This is what is done in VF. Bracket testing

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7
Q

Adjust method

A

allows the patient to adjust the brightness.

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8
Q

Patients with strict criteria

A

will not indicate they see a light until absolute certain. Will have false high thresholds

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9
Q

Patients with lax criteria

A

will hit whenever they think they may have seen it. Will have lower than expected thresholds. False positives.

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10
Q

Threshold for forced choice

A

75%

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11
Q

Signal detection theory

A

How a patient picks signal from background noise. The more separated S is from S+N the easier to detect.

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12
Q

Sensitivity

A

TP/TP + FN (population with disease)

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13
Q

Specificity

A

TN/TN+FP (population with/o disease)

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14
Q

Positive Predictive Value

A

Probability patient has disease if test is possible. TP/TP+FP

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15
Q

Negative Predictive Value

A

Probability patient doesn’t have disease if test is negative. TN/TN+FN

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16
Q

Receiver Operating Characteristic Curve

A

How a patients criteria affects the detectability of the signal. Lax will be up on to right. Strict will be low on the left.

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17
Q

Radiometry

A

Energy per time produced by a source of electromagnetic radiation.

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18
Q

Radiant power

A

The energy per second produced by a light source

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19
Q

Radiant Intensity

A

Energy per second in a given direction

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20
Q

Radiance

A

Like a megaphone of projected light

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21
Q

Irradiance

A

Light on a surface

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22
Q

Photometry

A

How our visual system detects electromagnetic radiation.

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23
Q

Luminous power

A

Visual systems response to light. Higher lumen=higher response=higher perception of brightness.

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24
Q

Luminous efficiency function

A

V=1 is the brightest and V=0 is the least bright

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25
Q

When does V=1 with photopic system

A

555 nm with 680 lumens/watt.

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26
Q

When does V=1 for scotopic system

A

507 with 1700 lumens/watt

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27
Q

Abney’s law of additivity

A

Can ad the V’s together if more than one wavelength in a light

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28
Q

Narrow band filters

A

Only allow a small range of wavelengths to pass through. Location of peak specifies which can pass and half-height bandwidths-A higher number=less sensitive.

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29
Q

Half height bandwidth

A

Larger number=less sensitive

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30
Q

Interference filters

A

Highly sensitive (low half height bandwidth) that only transmit a single wavelength

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31
Q

Broad band filters

A

allow a wide range of filters

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32
Q

Long pass filters

A

Transmit only long wavelengths. Change color perceptions.

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33
Q

Neutral density filters

A

Transmit all wavelength equal so no change in color perception. Will decrease light transmitted to eye and therefore will have a slower neural response

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34
Q

Pulfrich Phenomenon

A

Pendulum moves in an circle instead of back and forth. Over left=clockwise. Over right=counterclockwise.

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35
Q

Lambert surface

A

Surface that shows the same luminance in every angle or scatters light equally in all directions. ie. matte paper.. L=RE. If Luminance is doublbled so will L

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36
Q

Specular Surface

A

Surface that unequally scatters light. i.e. shinny piece of silver.

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37
Q

Retinal Illumination

A

T=LA. L=luminance A=area of pupil.

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38
Q

Scotopic vision

A

Poor visual acuity, lack of color discrimination, good sensitivity but poor resolution.

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39
Q

Photopic vision

A

Good VA, good color, poor sensitivity but good resolution (think amount PR to ganglion)

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40
Q

Mesopic conditions

A

when both rods and cones are active

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41
Q

Principal of Univariance

A

Although wavelength of photon affects its absorption, once it is absorbed all facts about it are lost.

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42
Q

When is photo chromatic interval zero

A

650 nm. Both are equally sensitive.

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43
Q

Purkinje shift

A

As illumination increases longer wavelengths appear brighter due to shift from scotopic to photopic system.

44
Q

Dark adaption curve

A

Expose to bright light and then track in dark. Cones first and then rods and then they take over

45
Q

When would there be no rod/cone break

A

650 nm.

46
Q

How would dark adaption curve shift for a stimulus of large wavelength?

A

It would take longer for rods to dominate as they are not sensitive at that wavelength.

47
Q

Dowling Rushton equation

A

Looks at dark adaption and only take photopigment regeneration into account.

48
Q

Light adaption

A

Light on a background of slightly different intensity. The intensity of the spot of light is adjusted until patient can just perceive the light against the background. The background intensity is then increased and patient’s threshold found again.

49
Q

Laws in light adaption

A

De-Vires and then weber.

50
Q

Fechner Log Law

A

Webers law holds true for stimuli above threshold.

51
Q

Steven’s Power law

A

Perceived brightness scales with stimulus intensity rather than logarthimatically.

52
Q

Spatial summation of photopic and scotopic

A

Scotopic has great spatial summation due to large pixels but poor resolution. Photopic has low spatial summation but great resolution.

53
Q

Critical diameter

A

The number of photons necessary to detect a given stimulus is the same for all stimulus sizes less than the critical diameter. Equal to the size of the pixel.

54
Q

Riccos Law

A

describes that the number of photons given a stimulus is constant when below critical diameter

55
Q

If the diameter is decreased the Intensity must be____

A

increased

56
Q

Critical Duration

A

The number of photons necessary to detect a given flash of light is the same for all duration of flashes that are less than the critical duration.

57
Q

Critical duration of scotopic vs. photopic

A

Critical duration is longer for scotopic system compared to photopic due to larger pixel in scotopic

58
Q

Bloch Law

A

Similar to Ricos law but for temporal summation. It=C1

59
Q

Stile-Crawford Effect

A

The angle at which light strikes a photoreceptor affects the perception of light.

60
Q

Which ray angle are cones most sensitive to?

A

Orthogonal to the surface.

61
Q

Trichromatic Theory

A

There are 3 different types of cone photoreceptors.

62
Q

S-cone

A

cyanolabe. 440 nm

63
Q

M-cone

A

Chlorolabe. 534

64
Q

L-cone

A

Erthyrolab. 564

65
Q

Rhodopism

A

498 nm

66
Q

Metamer

A

Two visual stimuli that are physically different but appear identical because they elicit the same response in all 3 cone photoreceptors.

67
Q

Color Opponency Theory

A

There are three channels for color vision. Red Green, blue yellow, brightness. Each channel treats two colors as opponents.

68
Q

R/G channel

A

Signal red for long and short wavelengths and green for medium

69
Q

B/Y channel

A

Will signal yellow for medium and long wavelengths and blue for short.

70
Q

Where do color opponent channels begin

A

At the ganglion cells.

71
Q

Saturation

A

How vivid is the color

72
Q

Chroma

A

Saturation

73
Q

Value

A

Brightnss

74
Q

Bezold-Brucke Phenomenon

A

The perception of hue associated with a given wavelength changes as the intensity of light is increased.

75
Q

Color constancy

A

Colors will appear the same even in different lightening conditions. Due to processing to maintain this.

76
Q

CIE Color system

A

You can combine red, green, and blue to create a stimulus that matches any other wavelength. 645, 536, 444.

77
Q

Red wavelength

A

645

78
Q

Green wavelength

A

526

79
Q

Blue wavelength

A

444 nm

80
Q

Protonopes

A

Missing the erytholabe pigment (564 nm). R-G color blindness. Red hues are very dim.

81
Q

Duternopes

A

Missing the chloro pigment (534 nm). R-G color blindness with no dimming.

82
Q

Tritanopes

A

Missing the cyan pigment (555 nm). B-Y color blindness.

83
Q

Protonomalous trichromat

A

The erthylabe pigment is shifted lower (like wearing a green filter). Red weak.

84
Q

Deuteranomalous trichromat

A

The cholorlabe pigment is shifter higher (like wearing a green filter) Green weak.

85
Q

X-chrom CL

A

Red tinted lenses that allow long pass filters. Shift the cone photoreceptor absorption spectra towards longer wavelengths. Can wear over one eye to increase color discrimination.

86
Q

Chromatic Discrimination

A

How much we need to change the wavelength of light in order to perceive a change in the hue of the stimulus.

87
Q

Color confusion lines

A

Only one photoreceptor is responding to the wavelengths on this line.

88
Q

Ichihara plates

A

No triatonpes and no nopes vs. anamolous

89
Q

HHR

A

No nope vs. anomalous but yes tritanopes.

90
Q

Kollner’s Rule

A

Outer retinal disease typically cause B/Y defects and inner retinal disease, ON, or visual pathway cause red-green defects.

91
Q

Chromatopias

A

Distortion of color but still have an ability to see colors

92
Q

A blurred lens will result in _____ image contrast, particularly at ______ spatial frequencies

A

Higher

93
Q

High spatial frequency cutoff

A

40-60 CPD

94
Q

Low spatial frequency cuttoff

A

4 CPD

95
Q

Snellen denominator to CPD

A

600/CPD=snellen denominator

96
Q

Why is there a high frequency cutoff?

A

Optical limitations and finit density of photoreceptors

97
Q

Why is there a low frequency cutoff?

A

Lateral inhibition of the retina

98
Q

March bands

A

If you gradually change luminance from end to the other you will actually just see march bands.

99
Q

Monocular Depth Cues

A

Pictorial depth cues, motion parallax

100
Q

Binocular Depth Cues

A

Uncrossed regional disparity (falling on nasal. Further away), crossed retinal disparity (falling on temporal. near)

101
Q

Motion detection

A

MT and V5

102
Q

Troxler phenomenon

A

Poor sensitivity for very low frequency stimuli and images will fade if we stare at it.

103
Q

Critical Flicker Fusion Frequency

A

If below=flicker. If above=constant

104
Q

Posterior lens perking image

A

Only one that is real, inverted, smallest. Formed by a concave.

105
Q

Maxwell’s spot

A

Blue wavelengths absorbed by the macula. Patient fixates a purple light he will perceive a red spot located at point of fixation because all blue light absorbed by macula

NBEO Part 1 (17 decks)

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