lecture 5

Question 1

define depth perception

Answer 1

being able to judge where things are in 3D

Question 2

how many forms of cues are there for depth perception

Answer 2

2:

- monocular and binocular

Question 3

binocular cues give you…

Answer 3

stereopsis

Question 4

list the monocular pictorial cues

Answer 4

relative size
occlusion (interposition)
relative height 
shadows
atmospheric perspective
linear perspective
familiar size
texture gradient

Question 5

list monocular movement produced cues

Answer 5

motion parallax

kinetic depth effect

Question 6

explain motion parallax

Answer 6

near objects pass retinal image plane faster than distance objects

Question 7

explain kinetic depth effects

Answer 7

when a 3D form of an object can be perceived when the object is moving

Question 8

how do we perceive depth and size?

Answer 8

oculomotor cues

Question 9

what is the monocular oculomotor cue?

Answer 9

accommodation

Question 10

what is the binocular oculomotor cue?

Answer 10

convergence

Question 11

explain how stereopsis is created

Answer 11

• Eyes located at different positions on the head —
• Binocular vision results in two slightly different (disparate) images are projected to the retinas —
• The disparities are processed in the visual cortex to yield depth perception (stereopsis) —
• The perception of depth and 3-dimensional structure is, possible with information visible from one eye alone however not as vivid as
  stereopsis

Question 12

are binocular disparities always present?

Answer 12

when looking at 3D objects - yes

when looking at 2D objects- need to be simulated by presenting 2 different images to each eye

Question 13

advantages of BSV

Answer 13

• stereopsis
• binocular summation
• better space perception
• hand eye coordination
• better reading
• seeing objects in camouflage

Question 14

what jobs would be difficult without stereopsis

Answer 14

• cannot be pilot by law
• dentistry
• sports
• seamstress
• jeweller
  etc

Question 15

define stereo acuity

Answer 15

smallest depth difference we can detect

Question 16

what effect does retinal disparity have on depth effect?

Answer 16

Greater the disparity the greater the depth effect

Question 17

what is the best stereopsis possible

Answer 17

2 secs of arc

Question 18

what is the average stereopsis

Answer 18

10 secs of arc

Question 19

what factors affect stereo thresholds (7)

Answer 19

• practice effects
• luminance
• exposure duration
• retinal eccentricity
• crowding effects
• motion in depth
• monocular blur

Question 20

what is more detrimental to stereoacuity? mono blur or binocular blur?

Answer 20

monocular blur

Question 21

why is it important to ensure anisemotropia is fully corrected?

Answer 21

monocular blur is more detrimental to stereoacuity than binocular blur

Question 22

when does stereopsis develop?

Answer 22

between 3-4 months

Question 23

when does stereopsis reach normal levels?

Answer 23

6 months

Question 24

at 9 years old, how many seconds of arc of stereopsis on Titmus?

Answer 24

40

Question 25

what is a qualitative method of measuring stereopsis? (total dissociation)

Answer 25

using the stereoscope or synoptophore

Question 26

how does the synoptophore work?

Answer 26

each eye has a different viewing tube two images presented one to each eye ask px if the arrows are pointing more towards the clinician or the Px if px says the arrows are pointing more towards themselves- no stereopsis towards clinicians - stereopsis?

Question 27

what are the methods of measuring stereopsis? (partial dissociation)

Answer 27

polarisation - Titmus (wire) - randot - mallet unit Red/green - TNO Optical -Lang

Question 28

titmus test uses polarised glasses, why?

Answer 28

to reduce monocular cues

Question 29

is the titmus test qualitative or quantitative?

Answer 29

can be both (fly is qualitative, animals and circles are quantitative)

Question 30

what distance is the titmus test carried out at

Answer 30

40 cm or 16"

Question 31

how many secs of arc is the fly in titmus?

Answer 31

3000

Question 32

how many secs of arcs are the animals in titmus?

Answer 32

100-500

Question 33

how many secs of arc are the circles in titmus?

Answer 33

40-500

Question 34

if you rotate the titmus by 90, will your px have depth perception?

Answer 34

no- the wings should be flat - use this as a test to see if they are lying

Question 35

does the randot test have monocular cues?

Answer 35

some due to part contour stimuli

Question 36

does the part random dot principle part of the randot test provide monocular cues?

Answer 36

no

Question 37

is randot test qualitative or quantitative?

Answer 37

quantitative

Question 38

how many secs of arc does the randot test measure ?

Answer 38

500- 20

Question 39

what viewing distance do you carry out the randot test at?

Answer 39

16" or 40 cm

Question 40

explain the mallet unit test?

Answer 40

you have 2 rows of symbols, try to fuse the two rows using 3 base out prism when fused the shapes will stick out

Question 41

how many secs of arc does the mallet unit test up to ?

Answer 41

10- 30

Question 42

viewing distance of mallet unit ?

Answer 42

36 cm

Question 43

why is it important to do the Mallett unit at 36 cm?

Answer 43

calibration will change with viewing distance

Question 44

how do you dissociate the 2 eyes in the TNO test

Answer 44

use red/green glasses

Question 45

how many screening plates in the TNO test

Answer 45

3

Question 46

how many secs of arc do the screening plates in TNO test up to?

Answer 46

1980

Question 47

how many quantitative plates are there in TNO test?

Answer 47

3 4 presentations on each plate – 2 presentations at each level

Question 48

how many secs of arc do the quantitative plates test up to?

Answer 48

480-15

Question 49

viewing distance of TNO test

Answer 49

40 cm

Question 50

who is the TNO test good for?

Answer 50

children people with special needs wearing glasses

Question 51

advantage of the TNO test

Answer 51

it tests up to 15 secs of arc with no monocular cues so good to use to test how good their stereopsis is

Question 52

who is lang test good for?

Answer 52

toddlers and children

Question 53

is lang a screening test?

Answer 53

yes

Question 54

which shape is a control shop ein lang test?

Answer 54

star

Question 55

how do you present lang plates

Answer 55

ask them what they can see

Question 56

viewing distance for lang 1 and 2

Answer 56

40 cm

Question 57

how many secs of arc does lang 1 test up to?

Answer 57

1200-550

Question 58

how many secs of arc does lang 2 test up to?

Answer 58

600-200

Question 59

which test have no dissociation

Answer 59

free space tests langs 2 pen frisby

Question 60

what do free space test entail?

Answer 60

perception of real depth | no 2D simulation

Question 61

what does the lang 2 pen test entail?

Answer 61

Patient and examiner each hold a pen vertically — Patient brings points of pens into contact — Cover one of patients eyes ◦ Repeat test — If accuracy poorer when using only one eye indicates presence of stereopsis under binocular conditions — Equal monocular and binocular response indicates absence of stereopsis

Question 62

why is langs 2 pen test a useful clinical tool

Answer 62

test low grade BSV or gross/coarse stereopsis

Question 63

is langs 2 pen quantitative or qualitative?

Answer 63

qualitative

Question 64

what does the frisby test entail?

Answer 64

``` Random array of shapes — 4 squares of shapes per sheet — One square contains a central circle — Observe behaviour or ask question about circles — Turn around sheet ask again — Responses seen in infants as young as 6 months — ```

Question 65

what thicknesses of sheets does the frisby test come in?

Answer 65

6mm, 3mm and 1 mm

Question 66

which fribky sheet tests better level of stereoacuity

Answer 66

1mm

Question 67

what is the disparity of a frisby sheet?

Answer 67

875-20"

Question 68

how can you change the level of stereoacuity measurable by the frisby sheets?

Answer 68

- increase viewing distance from 30-80 cm | - change the sheet thickness

Question 69

which test would you use for an under 2 year old?

Answer 69

land 1/2 or frisby

Question 70

which test would you use for someone who is about to decompensate?

Answer 70

frisby or lang 1/2

Question 71

which test would you use when you require the most accurate test and they are 8 years old?

Answer 71

TNO

Question 72

which test would you use for a child refusing to wear glasses?

Answer 72

lang 1/2 or frisby

Question 73

which test would you use for a home visit and you have no stereo-tests

Answer 73

lang 2 pen