Depth perception and Stereopsis

Question 1

What are the monocular cues for depth perception?

Answer 1

Lighting/shading
Texture gradient
Hue attenuation
Overlapping
Motion parallax
Linear gradient
Aerial perspective
Retinal image size
Accommodation

Question 2

What is the monocular cue lighting/shading?

Answer 2

Light or shade gives clues as to whether an object is pointing/moving towards or away from you

Question 3

What is the monocular cue texture gradient?

Answer 3

Textures become less detailed as they become further away from you

Question 4

What is the monocular cue hue attenuation?

Answer 4

The moisture particles in the air make objects appear a lighter hue when far away

Question 5

What is the monocular cue overlapping?

Answer 5

If one object is in front of another, it appears to overlap the object behind it

Question 6

What is the monocular cue motion parallax?

Answer 6

Closer objects appear to move faster than objects that are further away

Question 7

What is the monocular cue linear gradient?

Answer 7

Lines get closer together as they get further away from you

Question 8

What is the monocular cue aerial perspective?

Answer 8

seeing something from above indicates that it is far away

Question 9

What is the monocular cue retinal image size?

Answer 9

Known object sizes are used to judge how far away something is

Question 10

What is the monocular cue accommodation?

Answer 10

If accommodation is being used, you know that the object is closer (subconsciously)

Question 11

What are the binocular cues to depth perception?

Answer 11

Objective Fronto-parallel plane
Vieth-Muller circle
Horopter

Question 12

What is the Objective Fronto-parallel plane?

Answer 12

A straight plane in front of you, parallel to the plane which passes through the pupils.
Anything in front or behind the plane gives clues to depth

Question 13

What is the Vieth-Muller circle?

Answer 13

A circle encompassing the objects in front of you and their corresponding retinal points
Depth able to be perceived from awareness of which corresponding points are being stimulated

Question 14

What is the horopter?

Answer 14

Curved plane, all points stimulating corresponding retinal points
Able to tell depth from what is on the plane, just in front and behind in Panum’s area, and outside of Panum’s area

Question 15

What is binocular rivalry?

Answer 15

During physiological diplopia, the brain chooses the ‘better’ image to avoid double vision in the periphery. Often more dominant eye’s image chosen, but if image better in other eye, this will be chosen.

Question 16

For smaller stimuli, what type of dominance is used in binocular rivalry?

Answer 16

Exclusive - only one image used

Question 17

For larger stimuli, what type of dominance is used in binocular rivalry?

Answer 17

Mosaic - elements from each image used which are constantly shifting/alternating

Question 18

What details are prioritised during binocular rivalry?

Answer 18

Detail
Lines/contours
Movement
High contrast
Brighter
Flash

Question 19

Why does physiological diplopia occur?

Answer 19

Anything outside of Panum’s area is seen on non-corresponding points, so the cyclopean eye sees two of the object.

Question 20

What level of stereopsis are you able to measure up to in a normal clinic?

Answer 20

60” arc

Question 21

What is the timeline for stereopsis development?

Answer 21

Starts to develop at 3 months, rapid until 18 months, continues until at least 3 years old

Question 22

What factors affect/limit stereopsis?

Answer 22

Blur
Motion-in-depth
Temporal characteristics
Contrast sensitivity
Retinal eccentricity
Distance

Question 23

Why does blur affect/limit stereopsis?

Answer 23

Detail not as clear - unilateral is worse than bilateral bc harder to detect corresponding points

Question 24

Why does motion-in-depth affect/limit stereopsis?

Answer 24

Harder to locate corresponding points - more retinal disparity

Question 25

Why do temporal characteristics affect/limit stereopsis?

Answer 25

If something is seen for less time, then it's harder to gather information about it and coordinate corresponding points/retinal disparity

Question 26

Why does contrast sensitivity affect/limit stereopsis?

Answer 26

Higher contrast is easier to tell difference between things - unilateral is worse than bilateral

Question 27

Why does retinal eccentricity affect/limit stereopsis?

Answer 27

Further into periphery is worse due to lack of detail available to find retinal disparity

Question 28

Why does distance affect/limit stereopsis?

Answer 28

If something is further away, you can see less detail, so it's harder to distinguish corresponding points and therefore create retinal disparity

Question 29

What are the methods of assessing stereopsis?

Answer 29

Free fusion Auto-stereogram Anaglyphs Vectographs Transparent plates Synoptophore

Question 30

What kind of disparity is created when objects are behind the horopter?

Answer 30

Uncrossed disparity (image is on nasal retina)

Question 31

What kind of disparity is created when objects are in front of the horopter?

Answer 31

Crossed disparity (image is on temporal retina)

Question 32

What level can the Lang test up to?

Answer 32

100/200" arc

Question 33

What level can the TNO test up to?

Answer 33

60" arc (15" arc on older versions)

Question 34

What level can the Titmus test up to?

Answer 34

Fly: 800-3000" arc Circles: 800-40" arc Animals: 400-100" arc

Question 35

What level can the Frisby test up to?

Answer 35

600-5" arc

Question 36

What is point zero?

Answer 36

The point on the retina where the target's image falls in a strabismic eye

Question 37

What is confusion?

Answer 37

Different images are seen on each retina due to strabismus, with diplopia also present Brain cannot tell which image is 'correct'

Question 38

In an esot, where does the image fall and which field is it seen in?

Answer 38

Falls nasal to fovea Seen temporally

Question 39

In an exot, where does the image fall and which field is it seen in?

Answer 39

Falls temporal to fovea Seen nasally

Question 40

What is a suppression scotomata?

Answer 40

Area between the fovea and point zero where suppression occurs

Question 41

What are binocular adaptations to a strabismus/diplopia caused?

Answer 41

Suppression Abnormal retinal correspondence

Question 42

What are monocular adaptations to a strabismus/diplopia caused?

Answer 42

Amblyopia Eccentric fixation

Question 43

What does binocular adaptation mean?

Answer 43

It can only be present when both eyes are open/not covered

Question 44

During foveal suppression, does diplopia still occur?

Answer 44

Yes, in peripheral locations (anywhere that isn't within suppression scotomata)

Question 45

What is ARC?

Answer 45

The corresponding points in the retina of the strabismic eye are 'readjusted' so double vision doesn't occur Foveal suppression/scotomata are still present

Question 46

What is harmonious ARC?

Answer 46

Adjustment made = objective deviation size (Prism CT result) PZ becomes fixation point, lines up with fovea in fixating eye

Question 47

What is unharmonious ARC?

Answer 47

Adjustment made = subjective deviation size Fixation point is between fovea and PZ

Question 48

Why does unharmonious ARC occur?

Answer 48

Due to a change in the angle of the strabismus, normally from surgery or trauma

Question 49

What is amblyopia?

Answer 49

Reduced VA by at least 2 lines in one eye despite being fully corrected and no pathology present

Question 50

When can amblyopia be bilateral?

Answer 50

When there is high uncorrected astigmatism (meridional amblyopia)

Question 51

What are the causes of amblyopia?

Answer 51

Anisometropia Stimulus deprivation (congenital cataracts) Refractive error Strabismus Early eye disease Nutritional/toxic Idiopathic or congenital

Question 52

What is eccentric fixation?

Answer 52

Fovea doesn't take up fixation when fixating eye is covered bc the brain has 'moved' fovea to a different retinal point - so image is still on fixation point when covered

Question 53

What is EC with Identity?

Answer 53

The fixation point is on PZ, no movement on CT

Question 54

What is EC without Identity?

Answer 54

The fixation point is in between the fovea and PZ, some movement on CT

Question 55

What is intractable diplopia?

Answer 55

Constant, unchangeable diplopia