Spatial Vision 1

Question 1

This is related to variations in luminance across space

Answer 1

Spatial vision

Question 2

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

Answer 2

1. Visual Acuity

2. Contrast sensitivity

Question 3

What’s the primary way ODs measure spatial vision?

Answer 3

Psychophysical measure

Question 4

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

Answer 4

Minimal detectable acuity

Question 5

Our detection of acuity depends on:

Answer 5

Luminance or threshold of retinal image

Question 6

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

Answer 6

Decrement threshold task

Question 7

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

Answer 7

Increment threshold task

Question 8

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

Answer 8

Localization/Hyperacuity

Question 9

What are the 2 types of hyperacuity?

Answer 9

Spatial Interval acuity and Vernier Acuity

Question 10

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

Answer 10

Spatial interval acuity

Question 11

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

Answer 11

Vernier Acuity

Question 12

Optical defocus on localization/hyperacuity depends on what?

Answer 12

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

Question 13

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

Answer 13

Resolution Acuity

Question 14

The threshold for resolution acuity is what?

Answer 14

Minimum Angle of Resolution, MAR

Question 15

Resolution acuity depends on what two things?

Answer 15

1. Optics of the eye

2. Spacing of photoreceptors

Question 16

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

Answer 16

30-40 secs (0.5minutes)

Question 17

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

Answer 17

The tighter the PRs, the better the acuity

Question 18

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

Answer 18

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

Question 19

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

Answer 19

Resolution acuity

Question 20

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.

Answer 20

True

Question 21

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.

Answer 21

True

Question 22

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

Answer 22

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

Question 23

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

Answer 23

Easiest = L and T
Hardest = S and B

Question 24

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

Answer 24

1. Sloan Chart

2. Bailey Lovie

Question 25

Optical defocus effects all of the following except: a. Detection Acuity b. Hyperacuity c. Resolution Acuity d. Recognition Acuity

Answer 25

a. Detection Acuity

Question 26

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

Answer 26

Contrast

Question 27

What are the 4 attributes of sine wave grating?

Answer 27

1. Frequency 2. Contrast 3. Phase 4. Orientation

Question 28

What do frequency gratings look like?

Answer 28

Wide bars, larger differences between peaks and troughs

Question 29

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

Answer 29

Weber's fraction/formula

Question 30

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

Answer 30

Michaelson formula

Question 31

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

Answer 31

Peaks and Troughs would cancel out

Question 32

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

Answer 32

True

Question 33

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

Answer 33

Modulation Transfer Function (MTF)

Question 34

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

Answer 34

Spatial modulation transfer function (SMTF) of a lens

Question 35

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

Answer 35

mid to high spatial frequencies

Question 36

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

Answer 36

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

Question 37

What affects the high frequency drop-off of CSF?

Answer 37

Uncorrected refractive error, Cataracts

Question 38

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

Answer 38

On-center vs. Off-center ganglion responses

Question 39

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

Answer 39

Fourier Analysis

Question 40

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

Answer 40

Brightness Constancy

Question 41

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

Answer 41

Simultaneous contrast

Question 42

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

Answer 42

Assimilation

Question 43

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

Answer 43

Mach Bands

Question 44

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

Answer 44

high spatial frequency cut-off

Question 45

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

Answer 45

1. Generate CSF Curve | 2. Determine CS Threshold

Question 46

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

Answer 46

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

Question 47

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

Answer 47

1. Low contrast chart | 2. Multiple Contrast Chart

Question 48

What level of contrast is most practical for an adult?

Answer 48

2.5%

Question 49

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

Answer 49

Change working distance

Question 50

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

Answer 50

Glare

Question 51

What affect does glare have on contrast?

Answer 51

Reduces contrast

Question 52

What 3 things can cause glare?

Answer 52

1. Headlights 2. Cataracts 3. Post-Refrac. Sx

Question 53

This is shining light into the eye causing light scatter.

Answer 53

Veiling glare

Question 54

What are the 2 types of Veiling Glare?

Answer 54

1. Disability Glare | 2. Discomfort Glare

Question 55

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

Answer 55

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

Question 56

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

Answer 56

1. No loss of VA | 2. Loss of contrast

Question 57

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

Answer 57

True

Question 58

In low vision pts, reductions in CSF cause?

Answer 58

Issues with reading

Question 59

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

Answer 59

True

Question 60

Amblyopia causes what issues in contrast?

Answer 60

1. Loss at mid to high spatial frequencies | 2. Reduces VA

Question 61

Multiple sclerosis causes what issues in contrast?

Answer 61

1. Loss of contrast at low spatial frequencies | 2. Good contrast at high spatial frequencies (good VA)