Nbeo Visual Perception

Front 1

What is considered threshold for a non-forced choice psychometric function?

Back 1

50% correct line

Front 2

What are the percent correct ranges for a minimum detection psychometric function?

Back 2

0-100%

Front 3

What are the percent correct ranges for a forced choice psychometric function?

Back 3

50-100%

Front 4

What is considered threshold for a forced choice psychometric test?

Back 4

75% (half way between random chance and perfect)

Front 5

What is an example of the Method of Ascending/Descending Limits?

Back 5

Dark adaptation (increases the stimulus intensity incrementally and predictably)

Front 6

What is an example of the Method of Constant Stimuli?

Back 6

30-2 threshold (varies the stimulus intensity randomly)

Front 7

What is an example of the Stairstep Method?

Back 7

SITA fast (increase intensity step-wise followed by reversals to refine threshold)

Front 8

What is an example of the Adjustment Method?

Back 8

Nagel Anomaloscope

Front 9

What is the only psychometric method that is not affected by individual threshold criteria results?

Back 9

Forced Choice Method

Front 10

In Signal Detection Theory what corrupts the signal (S)?

Back 10

Noise (N)

Front 11

In terms of noise (N) and signal + noise (S + N), when is a signal easily detected?

Back 11

When the response to N is very different than the response to S + N (the detectability, d, is high).

Front 12

Are lax criteria for signal detection theory similar to high sensitivity or high specificity?

Back 12

High sensitivity (low specificity)

Front 13

Are strict criteria for signal detection theory similar to high sensitivity or high specificity?

Back 13

High specificity (low sensitivity)

Front 14

What is the probability that a test giving a positive result will actually be positive?

Back 14

Sensitivity

Front 15

What is the probability that a test giving a negative result will actually be negative?

Back 15

Specificity

Front 16

What is the probability that a disease will actually be present given that the test is positive?

Back 16

Positive predictive value

Front 17

What is the probability that a disease will actually not be present given that the test is negative?

Back 17

Negative predictive value

Front 18

Is a Type I error a false positive or a false negative?

Back 18

False positive (low specificity)

Front 19

Is a Type II error a false positive or a false negative?

Back 19

False negative (low sensitivity)

Front 20

False negative rate = 1 - (?)

Back 20

Sensitivity

Front 21

False positive rate = 1 - (?)

Back 21

Specificity

Front 22

(True positives) / (True positives + False positives) = ?

Back 22

Positive predictive value

Front 23

(True negatives) / (True negatives + False negatives) = ?

Back 23

Negative predictive value

Front 24

What is the term for an observer correctly detecting a signal?

Back 24

Hit

Front 25

What type of measurement deals with electromagnetic radiation?

Back 25

Radiometry (deals with physical properties that are easy to measure)

Front 26

Radiant power or watts (W) =

Back 26

E/s

Front 27

How does radiant intensity differ from radiant power?

Back 27

Intensity has to do with the energy in a given direction rather than the total energy emitted.

Front 28

What do you have to take into account to measure radiance?

Back 28

The size of the source.

Front 29

What is the difference between radiance and irradiance?

Back 29

Irradiance has to do with the area on which the light is projecting, not the size of the light.

Front 30

What is the difference between Radiometry and Photometry?

Back 30

Photometry is an indirect measure of how our visual system responds to radiometry.

Front 31

Does photometry have to do with perception or the physics of light?

Back 31

Perception

Front 32

What is luminous power analogous to?

Back 32

Radiant power

Front 33

What is luminous intensity analogous to?

Back 33

Radiant intensity

Front 34

What is luminance analogous to?

Back 34

Radiance

Front 35

What is illuminance analogous to?

Back 35

Irradiance

Front 36

What are the units of radiant power and luminous power?

Back 36

Watts and Lumens

Front 37

What are the units of radiant intensity and luminous intensity?

Back 37

Watts or Lumens per solid angle (has to do with direction of the light)
Lumen/solid angle = candela

Front 38

What are the units of luminance?

Back 38

Candelas/m^2 or nits
(still takes intensity, or the direction of the light, into account)

Front 39

What are the units of illuminance?

Back 39

Lumens/area of surface (lux)
(doesn't have anything to do with intensity (direction) of the source, just power)

Front 40

How can you converts a physical property into a perceptual property using radiant and luminous power?

Back 40

The average human perception of the power of light at 555nm is 680 lumens/W. Now we have put perception (lumens) and physics (Watts) together.

Front 41

What is a foot candle?

Back 41

Just another measure of illuminance (1 foot-candle = 10.8 lux)

Front 42

How can we convert from the physical power of light to the perceptual power under scotopic conditions?

Back 42

There are 1700 lumens/W at 507nm (where rods are most sensitive)

Front 43

What happens to luminous power (lumens) when you combine two light sources.

Back 43

They add together (Abney's Law of Additivity)

Front 44

For a narrow band filter, you can measure the selectivity of the filter. What is this called?

Back 44

Half height bandwidth (higher bandwidth means less sensitive)

Front 45

Do interference filters have high sensitivity or low sensitivity to a wavelength?

Back 45

High sensitivity (essentially transmit a single wavelength)

Front 46

What kind of filter transmits a large range of wavelengths?

Back 46

Broad band (think higher half height bandwidth)

Front 47

What kind of filter transmits all wavelengths equally? What is it used for in clinic?

Back 47

Neutral density filter. Used for measuring an RAPD in ONH disease.

Front 48

What kind of filters do most sunglasses use? Why is this kind of filter desirable?

Back 48

Neutral density - it doesn't distort colors

Front 49

What kind of surface scatters light equally in all directions?

Back 49

Lambert surface

Front 50

What kind of surface reflects light with equal luminance at all viewing angles?

Back 50

Specular surface

Front 51

As you increase luminance, how does illuminance change?

Back 51

It increases proportionally (linear relationship)

Front 52

How is retinal illumination (T) related to luminance of a surface (L) and area of the pupil (A)

Back 52

T = LA

Front 53

As a light source is pulled away from a surface (d doubles), what happens to the illumination on the surface?

Back 53

It decreases by the square of the distance (in this case, decreases by 1/4).

Front 54

Do photoreceptors actually respond to light in a wavelength-dependent manner?

Back 54

No - the wavelength of the photon only determines the probability of absorption and after that, the wavelength information is lost (Principle of Univariance)

Front 55

Why are there ambiguities between color (based on wavelength) and intensity (based on direction) of light?

Back 55

The Principle of Univariance - all information about the wavelength of a photon is lost when it is absorbed.

Front 56

The photochromatic interval shows the difference in photopic and scotopic __________ at a given wavelength.

Back 56

Sensitivity

Front 57

At which wavelength is the photochromatic interval zero? What does this mean?

Back 57

at 650nm. This means that our SENSITIVITY under photopic and scotopic conditions are equal.

Front 58

Why do longer wavelengths start to appear brighter as we shift to photopic viewing conditions?

Back 58

Cones start to take over for the rods (Purkinje Shift)

Front 59

What is different about cones and rods that leads to the Purkinje Shift?

Back 59

Cones absorb light at 555nm and rods at 507nm. The longer wavelengths start to appear brighter.

Front 60

For a single wavelength, we can plot our threshold to light as we spend more time in the dark. What is this kind of graph called?

Back 60

Dark adaptation curve.

Front 61

What will be different about a dark adaptation curve at 650nm?

Back 61

There will be no rod-cone break.

Front 62

Why does photopigment bleaching account for at least part of the dark adaptation curve?

Back 62

Rods are bleached under bright conditions and it takes time for them to regenerate. As the number of unbleached rods increases, the probability of absorption, or sensitivity, increases

Front 63

The Dowling-Rusthon Equation is used to help describe what phenomenon?

Back 63

Dark adaptation

Front 64

How do we measure light adaptation?

Back 64

Find the person's threshold for light at a given background intensity.

Front 65

How do the axes for the dark adaptation curve differ from the axes for a light adaptation curve?

Back 65

Dark adaptation is based on signal detection with time while light adaptation is based on signal detection (JND) with background intensity.

Front 66

How is a light adaptation curve constructed?

Back 66

Find the JND (difference between signal and background) for a series of different background intensities.

Front 67

Which kind of curve is described by the DeVries-Rose Law? What does it state?

Back 67

Light adaptation. It says that there is a certain point at which vision is dominated by fluctuations in background light. The JND does not increases as quickly as the background intensity.

Front 68

Which kind of curve is described by Weber's Law? What does it state?

Back 68

Light adaptation. It says there is a certain point at which the JND increases at the same rate as the background intensity.

Front 69

What percentage of rods need to be bleached to reach rod saturation?

Back 69

10%

Front 70

Why is there a break in the light adaptation curve?

Back 70

This is the point when rods are saturated and cones take over.

Front 71

Once rods are saturated, what law does the light adaptation curve follow?

Back 71

Weber's law (background intensity and JND increase at the same rate).

Front 72

When do cones become saturated?

Back 72

Never

Front 73

Is Steven's or Fechner's law more accurate for actual observed behavior?

Back 73

Steven's

Front 74

What does Fechner's law assume?

Back 74

That Weber's law holds above threshold.

Front 75

What does Steven's Law show?

Back 75

Sensation increases much more quickly than expected with stimulus intensity.

Front 76

What is the biophysical explanation for Spatial summation?

Back 76

There are many rods to one ganglion cell.

Front 77

Match the following:
Ricco's Law or Bloch's Law with
Temporal summation or spatial summation

Back 77

Ricco's: spatial
Bloch's: temporal

Front 78

How does the retina control marginal rays in photopic vision?

Back 78

Stiles-Crawford Effect (does not occur with rods)

Front 79

Which cone system is most susceptible to damage?

Back 79

S cones

Front 80

What law describes metamers?

Back 80

Grassman's

Front 81

What is Color Opponency Theory? What does it explain?

Back 81

Red opposes green
Blue opposes yellow
Brightness also comes into
It explains the fact that cone peak sensitivities do not correspond perfectly with perceptual sensitivities.

Front 82

What is the perception of wavelength?

Back 82

Hue

Front 83

What system relates hue, saturation (or chroma), and brightness (or value)?

Back 83

Munsell Color Appearance System

Front 84

What phenomenon states that our perception of hue depends a little on our perception of brightness?

Back 84

Bezold-Brucke

Front 85

What is color constancy?

Back 85

Colors appear the same in different lighting conditions (there is higher-order processing going on)

Front 86

What can the CIE system do for us clinically?

Back 86

It can show us the color confusion lines of a color-deficient person.

Front 87

What colors do a protanope and deuteranope confuse?

Back 87

Red, orange, yellow, and green. (red appears dimmer, green brighter)

Front 88

What colors do a tritanope confuse?

Back 88

Blues, yellows

Front 89

Who will shift in longer wavelengths during testing?

Back 89

Protanomalous trichromat

Front 90

Who will shift in shorter wavelengths during testing

Back 90

Deuteranomalous trichromat

Front 91

What 2 lighting conditions are acceptable for Ishihara color testing?

Back 91

Daylight
Macbeth Illuminant C lamp

Front 92

What advantage does Ishihara have over Farnsworth?

Back 92

It can classify severity

Front 93

What advantage does Farnsworth have over Ishihara?

Back 93

It can distinguish the category of color deficiency

Front 94

How is the Nagel Anomaloscope limited?

Back 94

It only does red-green defects.

Front 95

What is normal mix:test expected on Nagel?

Back 95

45:17

Front 96

What to expect for a protanope on Nagel (mix:test)

Back 96

very low : very high
very high : very low

Front 97

What to expect for a deuteranope on Nagel (mix:test)

Back 97

anything : 17

Front 98

What to expect for a protanomaly on Nagel (mix:test)

Back 98

higher : normal

Front 99

What to expect for a deuteranomaly on Nagel (mix:test)

Back 99

normal: lower

Front 100

What is Kollner's rule

Back 100

Outer retina: blue-yellow (think glaucoma)
Inner retina: red-green (think genetic)

Front 101

What is a chromatopsia?

Back 101

Distortion of color, not a problem discriminating (can tell something is blue, it just looks a lot bluer than normal)

Front 102

What is the ability for a system to transmit a sin-wave grating clearly to the other side?

Back 102

Spatial Modulation Transfer Function

Front 103

How do you convert cycles/degree to a Snellen fraction?

Back 103

600/(cycles per degree) = Snellen denominator

Front 104

What is the peak CSF?

Back 104

4 cycles/degree (20/150)

Front 105

What is the high spatial frequency cutoff?

Back 105

60 cycles/degree (20/20)

Front 106

What limits the high frequency cutoff for vision?

Back 106

Optics, photoreceptor density

Front 107

What limits the low frequency cutoff for vision?

Back 107

Lateral inhibition

Front 108

How does Fourier analysis describe vision?

Back 108

The visual system breaks scenes down into various frequency components then reassembles them.

Front 109

What visual phenomenon suggests that the visual system is breaking the scene down into individual frequency components and handling them separately?

Back 109

Mach Bands

Front 110

If the image falls on the nasal side of the retina, does the object appear closer or farther away?

Back 110

Farther (this occurs during uncrossed disparity)

Front 111

What clinical test looks at the magno system?

Back 111

Random-dot kinematogram

Front 112

How is the CFF analogous to the CSF?

Back 112

Threshold of detection of flicker frequency vs. spatial frequency

Front 113

What flicker frequencies are lost in glaucoma?

Back 113

Moderate and high frequencies

Front 114

Does peripheral or central retina detect flicker better?

Back 114

Peripheral retina (Granit-Harper)

Front 115

Light flashes appear brightest when shown for what duration?

Back 115

50-100msec (Broca-Sulzer Effect)

Front 116

Does flickering light appear different than steady light of the same luminance?

Back 116

Yes - it appears brighter (Brucke-Bartley) but only if we can see it flickering - below CFF (Talbot-Plateau)

Front 117

For which kind of masking does the mask appear first? Metacontrast, Paracontrast, or Simultaneous?

Back 117

Paracontrast

Front 118

What kind of masking effect causes crowding in amblyopia?

Back 118

Simultaneous masking

Front 119

Does central or peripheral retina see low spatial frequencies better?

Back 119

Peripheral

Front 120

How are glaucoma and dyslexia related?

Back 120

The magno pathway is suspected to be deficient in both.