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PPMV 2 > Spatial Vision 1 > Flashcards

Spatial Vision 1 Flashcards

1
Q

This is related to variations in luminance across space

A

Spatial vision

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2
Q

The ability to resolve or discriminate spatially visual stimuli is measured with what 2 things?

A
  1. Visual Acuity

2. Contrast sensitivity

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3
Q

What’s the primary way ODs measure spatial vision?

A

Psychophysical measure

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4
Q

This is the angular size of the smallest object that can just be seen?

A

Minimal detectable acuity

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5
Q

Our detection of acuity depends on:

A

Luminance or threshold of retinal image

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6
Q

Detection of a lower luminance region against a higher luminance field is called:

A

Decrement threshold task

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7
Q

Detection of a higher luminance region against a lower illuminated field is called:

A

Increment threshold task

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8
Q

This is the smallest spatial offset or difference in location between targets that can be discriminated

A

Localization/Hyperacuity

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9
Q

What are the 2 types of hyperacuity?

A

Spatial Interval acuity and Vernier Acuity

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10
Q

This is the smallest separation and change between 2 targets that can be discriminated as smaller or larger compared to other targets

A

Spatial interval acuity

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11
Q

This is telling if there’s a slight break in a single, straight line; how much of an offset can be detected.

A

Vernier Acuity

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12
Q

Optical defocus on localization/hyperacuity depends on what?

A

depends on the separation of the targets

  • If close together (<10-15) = threshold increase
  • If farther apart (1 deg) = defocus has less of an effect
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13
Q

This is the smallest spatial separation between 2 nearby points or lines that can be discriminated as 2 vs. 1; minimum separable or resolvable acuity

A

Resolution Acuity

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14
Q

The threshold for resolution acuity is what?

A

Minimum Angle of Resolution, MAR

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15
Q

Resolution acuity depends on what two things?

A
  1. Optics of the eye

2. Spacing of photoreceptors

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16
Q

In the human eye, resolution acuity can be as good as?

A

30-40 secs (0.5minutes)

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17
Q

What allows for vision of 20/10 or 20/15 VA?

A

The tighter the PRs, the better the acuity

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18
Q

What are the 3 clinical limitations of resolution acuity as space between the lines increase?

A
  1. They appear thicker
  2. @ high luminance levels, spread into each other
  3. Astigmatism defocuses along one meridian
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19
Q

What test is good for nonverbal or TBI patients to determine their visual acuity?

A

Resolution acuity

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20
Q

T/F: Grating acuity is less impacted by optical defocus than a standard letter chart. A patient will have a better VA with grating acuity than snellen acuity.

A

True

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21
Q

T/F: Dioptric blur had a strong negative effect on Snellen Acuity but had little effect on grating acuity. Snellen letters are more sensitive than gratings to a patient’s refractive error.

A

True

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22
Q

This is the ability to recognize the smallest details in a letter or picture. This is most commonly used clinically

A

Identification/Recognition Acuity (can be considered a type of resolution acuity)

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23
Q

Which letters are the easiest and hardest to identify on a Snellen chart?

A 
Easiest = L and T
Hardest = S and B
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24
Q

What recognition acuity charts with less “confusion” letters on the same line with equal spacing and no serifs?

A
  1. Sloan Chart

2. Bailey Lovie

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25
Q

Optical defocus effects all of the following except:

a. Detection Acuity
b. Hyperacuity
c. Resolution Acuity
d. Recognition Acuity

A

a. Detection Acuity

26
Q

This is our ability to process complex patterns of light and dark under a variety of luminance conditions

A

Contrast

27
Q

What are the 4 attributes of sine wave grating?

A
  1. Frequency
  2. Contrast
  3. Phase
  4. Orientation
28
Q

What do frequency gratings look like?

A

Wide bars, larger differences between peaks and troughs

29
Q

What formula is used to measure visual contrast for optotypes (letters, numbers or pictures)?

A

Weber’s fraction/formula

30
Q

What formula is used to measure visual contrast of gratings??

A

Michaelson formula

31
Q

If 2 gratings are almost 180 degrees apart (out-of-phase), what would happen?

A

Peaks and Troughs would cancel out

32
Q

T/F: Spatial square wave reading is much more complicated than sine wave grating.

A

True

33
Q

The ability of an optical system to transmit spatial frequencies is what?

A

Modulation Transfer Function (MTF)

34
Q

This is the amount of information transferred by the lens as a function of spatial frequency.

A

Spatial modulation transfer function (SMTF) of a lens

35
Q

If the image is defocused, then the image drops off at the ___ to ___ spatial frequencies.

A

mid to high spatial frequencies

36
Q

This is the measurement of one’s sensitivity or what they perceive.

A

Contrast Sensitivity Function (CSF) - a type of psychophysical measurement

37
Q

What affects the high frequency drop-off of CSF?

A

Uncorrected refractive error, Cataracts

38
Q

What affects the low frequency drop-off (wider stripes)?

A

On-center vs. Off-center ganglion responses

39
Q

This is a method to define periodic waveforms by trigonometric function.

A

Fourier Analysis

40
Q

This states the brightness of objects doesn’t vary despite changes in absolute luminance

A

Brightness Constancy

41
Q

This states the relative brightness of an object increases or decreases depending on the background

A

Simultaneous contrast

42
Q

This states the brightness of a stimulus co-varies with the brightness of a surrounding stimulus

A

Assimilation

43
Q

This is the emphasis of contrast coundaries associated with edges due to luminance boundaries noted by the retinal ganglion cells

A

Mach Bands

44
Q

In our standard optometric exam, with respect to contrast sensitivity, what do we measure?

A

high spatial frequency cut-off

45
Q

How do we clinically test Contrast Sensitivity Function (CSF)?

A
  1. Generate CSF Curve

2. Determine CS Threshold

46
Q

What 3 tests can we use to generate a CSF curve?

A
  1. Arden Plates
  2. Visitech Vision CTS
  3. Functional Acuity Contrast Test (FACT)
47
Q

What 2 types of charts can be used to measure contrast sensitivity threshold?

A
  1. Low contrast chart

2. Multiple Contrast Chart

48
Q

What level of contrast is most practical for an adult?

A

2.5%

49
Q

How can we change the VA of someone using a Pelli Robson chart?

A

Change working distance

50
Q

This is when ambient light interferes with increment or different threshold detections

A

Glare

51
Q

What affect does glare have on contrast?

A

Reduces contrast

52
Q

What 3 things can cause glare?

A
  1. Headlights
  2. Cataracts
  3. Post-Refrac. Sx
53
Q

This is shining light into the eye causing light scatter.

A

Veiling glare

54
Q

What are the 2 types of Veiling Glare?

A
  1. Disability Glare

2. Discomfort Glare

55
Q

Disability glare is caused by car headlights. What are 2 side effects? Main contributor??

A
  1. Decreased VA
  2. Reduction in contrast
    = mainly caused by cataracts
56
Q

Discomfort glare is caused by CL corneal edema, etc. What are the 2 SEs?

A
  1. No loss of VA

2. Loss of contrast

57
Q

T/F: 20/20 VA measures high spatial frequency cut-off only. (Bottom right corner of CSF graph)

A

True

58
Q

In low vision pts, reductions in CSF cause?

A

Issues with reading

59
Q

T/F: The poorer the contrast sensitivity the greater the visual disability

A

True

60
Q

Amblyopia causes what issues in contrast?

A
  1. Loss at mid to high spatial frequencies

2. Reduces VA

61
Q

Multiple sclerosis causes what issues in contrast?

A
  1. Loss of contrast at low spatial frequencies

2. Good contrast at high spatial frequencies (good VA)

PPMV 2 (15 decks)

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