Block 09 > mono: spatial vision > Flashcards

mono: spatial vision Flashcards

(75 cards)

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1
Q

Spatial vision is concerned with variations in luminance across _________

A

Space

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2
Q

Spatial vision is the visual system’s ability to __________ and _________

A

Detect and Resolve

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3
Q

The visual system recognizes objects from patterns of ________ and ________

A

Light and dark

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4
Q

The visual system processes spatial luminance information in a manner that emphasizes the _____________ difference that typically occur in the boundaries or edges of objects

A

Luminance

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5
Q

Absolute luminance is ________ important in spatial vision than relative luminance

A

Less

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6
Q

Is the brightness of an object always predicted by its luminance?

A

No

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7
Q

Brightness of an object depends on _________ more than on absolute luminance

A

Contrast

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8
Q

How would a square surrounded by a background with higher luminance appear compared to a square surrounded by a background with lower luminance?

A

The square surrounded by the background with higher luminance will appear darker

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9
Q

The brightness of a center panel is affected by the ___________ at the boundary between the center panel and surrounding background panels

A

Local contrast

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10
Q

Positive contrast __________ the brightness

A

increases

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11
Q

Negative contrast __________ the brightness

A

decreases

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12
Q

___________ boundaries provide critical information on perception

A

Contrast

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13
Q

Contrast at the boundaries tends to be __________ on the side in which the original area was light

A

Lighter

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14
Q

Contrast at the boundaries tends to be __________ on the side in which the original area was dark

A

Darker

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15
Q

Mach bands are visual systems way of ____________ luminance differences

A

Highlighting

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16
Q

The sensitivity of the visual system to spatial luminance changes is measured with ____________________ of varying frequency and contrast

A

Sinewave gratings

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17
Q

A sine-wave grating is useful for studying the ______________

A

Thresholds of the visual system recognizes

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18
Q

The peak of the luminance profile corresponds to a ___________ bar of the grating

A

Bright

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19
Q

The trough of the luminance profile corresponds to a _________ bar of the grating

A

Dark

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20
Q

The transition from bright to dark bars is a ___________ transition, not an abrupt transition

A

Gradual

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21
Q

Two characteristics of a sine-wave grating are ___________ and ___________

A

Frequency and contrast

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22
Q

The spatial frequency of a grating can be specified by __________________________ or _____________________

A

Number of cycles/degree of visual angle

Number of cycles per unit of space

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23
Q

Does higher contrast or lower contrast show higher amplitude?

A

High contrast

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24
Q

Contrast equation

A

= Δ l/l average

Δl = the difference between the peak and average luminance.
l ave = the average luminance of the grating (the average of the light peaks and dark troughs)

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25
Michelson equation
Contrast = lmax - lmin / lmax + lmin
26
Contrast ranges between _______ and ______ %
0 and 100%
27
The spatial frequency depends on the _________ of the lens
Magnification
28
The modulation depth (contrast) depends on the __________ of the lens
Quality
29
For a real lens, as the spatial frequency becomes greater and greater, the amplitude of modulation of the image distribution becomes ___________ and __________
Smaller and smaller
30
Contrast or modulation can be defined as.....
How faithfully the minimum and maximum intensity values are transferred from object plane to image plane
31
Optical transfer function includes both the ______ and ______
MTF (modulation transfer function) ## Footnote PTF (Phase transfer function)
32
MTF is a function of _____
Spatial frequency/resolution
33
The MTF of a lens is a measurement of its ability to transfer _________ at a particular resolution from object to image
Contrast
34
MTF is a way to incorporate ___ and __ into a single specification
resolution and contrast
35
As line spacing decreases (the frequency increases) on the test target, it becomes difficult for the lens to efficiently transfer this decrease in contrast; as a result, MTF _____________
Decreases
36
What is the phase shift across a range of spatial frequencies?
Phase Transfer Function
37
On-axis in a rotationally symmetric optical system, is there a change with spatial frequency? What does this mean for PTF?
No ## Footnote PTF = 0 OTF = MTF
38
Lens transfer information = _________ / ___________
Image contrast / object contrast
39
For a perfect lens, image contrast = _____________
Object contrast
40
For a real lens, image contrast = ___________ - ___________
Object contrast - image degradation
41
How do aberrations impact image quality at low and moderate spatial frequencies compared to high frequencies?
Have little effect on optical image quality
42
Optical defocus on SMTF results in a reduction in image quality primarily at ______ spatial frequencies
High
43
How is the effect of Translucent optics on SMTF?
SMTF reveals an overall reduction in image contrast at all frequencies
44
Contrast sensitivity function (CSF) is a function describing how the sensitivity to __________ (defined as the reciprocal of the contrast threshold) depends on the ___________ _________ (size) of the stimulus.
Contrast ## Footnote Spatial frequency
45
The reciprocal of the contrast threshold is the contrast ____________
Sensitivity
46
Human contrast sensitivity: Maximum sensitivity is ________________
4 cycles/degree
47
As the spatial frequency of a 100% contrast grating is increased, a point is reached at where the grating can no longer be resolved. This point is represented on the CSF as the _____________
High-frequency cutoff
48
For a young, healthy adult, the high-frequency cutoff can be approximately ________________
60 cycles/degree
49
As the patient reads down an eye chart, the high spatial frequency content __________
Increases
50
The point at which the details of the optotypes can no longer be resolved is the patients _______________, which is essentially the _____________________
Visual acuity ## Footnote High-frequency CSF cutoff
51
The typical clinical acuity measurement only tests a very limited aspect of the patients spatial vision, which is the _______________
High spatial frequency cutoff
52
What 2 ways explain why the visual system shows a reduction in sensitivity for high frequencies?
1. Optical limitations 2. Packing density of retinal photoreceptors
53
Any optical system, including the eye, manifests a high-frequency limitation because of ____________________
Optical aberrations
54
What happens to the high-frequency cutoff if the eye is out-of-focus, such as in uncorrected myopia?
There is a reduction in the high-frequency cutoff due to the decreased visual acuity
55
Peak sensitivity for the CSF of a typical adult
4 cycles/degree
56
CSF - high spatial frequency cutoff
60 cycles/degree
57
A typical ganglion cell receptive field consists of a __________ region that responds to illumination with excitation or inhibition AND a __________ region that responds with the opposite sign. What is this called?
Center region ## Footnote Surround region Spatial antagonism, also called lateral inhibition
58
For the receptive field, light falling on the center causes ____________, while light falling on the surrounding causes _____________
Excitation ## Footnote Inhibition
59
A lower spatial frequency, where the bright bar falls on both the receptive field's center and surround, thereby causing lateral inhibition, results in a ___________ response.
Smaller
60
What might be the basis for the CSFs low-frequency drop off?
Spatial antagonism/lateral inhibition
61
VA determined with optotypes is equivalent to the ___________________
CSF High-frequency cutoff
62
The angle that just resolvable bars (or gaps) make with the eye is called the ___________
MAR (minimum angle of resolution)
63
The combination of the bar and a gap, which is equivalent to one complete cycle of a grating, is ________ the MAR
Twice
64
An individual bar, which is the grating's detail and represents the patient's MAR, subtends _______ of a degree.
0.5/60
65
Equation to use for High-frequency cutoff/Snellen fraction and Cycles/degree questions
600 / Snellen denominator = cycles/degree ## Footnote 600/cycles/degree = Snellen denominator
66
What is the expected high-frequency cutoff of a patient with 20/40 acuity?
15 cycles/degree
67
Express Snellen 20/10 in cycles per degree.
60 cycles/degree
68
Convert 30 cycles/degree to Snellen
20/20
69
Convert 40 cycles/degree to Snellen
20/15
70
Express Snellen 20/80 in cycles per degree.
7.5 cycles/degree
71
Express Snellen 20/100 in cycles per degree.
6 cycles/degree
72
Express Snellen 20/60 in cycles per degree.
10 cycles/degree
73
What is test-retest variability (TRV)?
A patient's measured VA may vary upon repetition even when there has been no change in the patient's visual status
74
_________ spatial frequency content is an important contributor to Test-Retest Variability (TRV)
Low
75
What new test has been designed to help correct against Test-Retest variability?
A test that removes low spatial frequencies from the optotypes. Creating high-pass optotypes. (Vanishing optotypes)
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