Intro To Binocular Vision Exam Final (New)

Front 1

horitzontal disparity

Back 1

1. Absolute disparity of a single object
2. Relative disparity of two or more objects
3. Disparity gradient and disparity curvature

Front 2

The Pulfrich Phenomenon (Effect)

Back 2

An object swinging in the frontoparallel plane appears to be traveling in an elliptical pattern toward and away from the observer in depth when there is a lower luminance contrast in one of the observer’s eyes

Front 3

Chromostereopsis

Back 3

1. Surface areas of different colors in the same vertical plane appear to be at different distances from the eyes
2. binocular effects of transverse chromatic aberration
3. true stereoscopic effect and it disappears when one eye is covered.

Front 4

Clinical conditions that can initiate the Pulfrich effect...

Back 4

1. optic neuritis
2. anisocoria
3. monocular cataract
4. corneal scar
5. ocular pathologies that affects one eye to a much greater extent than the other

Front 5

what is the relationship between temporal delay and spatial disparity

Back 5

Temporal delay is GEOMETRICALLY EQUIVALENT to spatial disparity

Front 6

absolute disparity:
definition
formulas

Back 6

1. an object whose image falls on non-corresponding retinal points
2. difference in the visual angles subtended by a single obj at each eye
3. difference between binocular parallax and vergence of an obj

Front 7

what is relative disparity

Back 7

the difference between the absolute disparities of two points

Front 8

relationship between relative disparity and fixation distance

Back 8

Changes in vergence cause changes the absolute disparities of objects, while relative disparity does not change with fixation distance

Front 9

Disparity Curvature

Back 9

describes changes of disparity gradient over visual angle

Front 10

vertical disparities

Back 10

1. arise when an object is nearer to one eye than to the other
2. may also arise from ANISEIKONIA or STRABISMUS

Front 11

motion parallax:
definition

Back 11

1. monocular depth cue
2. obtaining spatial disparity by one eye moving from one to another position through IPD successively

Front 12

Shape from Motion

Back 12

A flat moving object give rises to the percept of a three- dimensional object rotating in depth

Front 13

Depth tilt from interocular spatial- frequency differences

Back 13

When vertical sine wave gratings of different frequencies in the two eyes are fused, tilt (slant) around a vertical axis is perceived

Front 14

what is the difference between stereoacuity and stereopsis

Back 14

1. Stereopsis:
the unique sense of depth discrimination arising from the binocular cue of relative horizontal disparity.

2. Stereoacuity:
used to measure the intactness of binocular vision (the smallest stereoscopic depth interval we can perceive)

Front 15

Stereoacuity for humans:

Back 15

1. a form of hyperacuity (better than predicted by PR sampling)
2. 4-5 arc sec
3. 95-98% of population achieves stereoacuity of better than 40 arc sec

Front 16

what method of test is used when measuring stereoacuity

Back 16

1. method of constant stimuli
2. two alternative forced choice method
3. two stimuli: 1)reference has zero disparity 2)test has crossed or uncrossed disparity

Front 17

describe the Howard-Dolman Stereoacuity Test

Back 17

set up:
1. two rods
2. One rod is at a fixed location, the other rod is movable
3. subject views the rods through an aperture

METHOD OF ADJUSTMENT

Front 18

ANGULAR DISPARITY
what is the relationship of disparity and depth interval

Back 18

n=(PD/(test distance^2))(change in distance)

Front 19

what are the factors that affect stereoacuity

Back 19

1. Luminance
2. Exposure duration
3. Contrast Color
4. Optical blur
5. Target separation/crowding
6. Retinal Eccentricity
7. Practice
8. Stimulus Motion

Front 20

how does LUMINANCE affect stereoacuity

Back 20

Dimmer background luminance results in less sensitivity to disparity and the perception of depth from disparity

Front 21

how does EXPOSURE DURATION affect stereoacuity

Back 21

1. short exposure=elevated threshold
2. best stereothreshold is achievable f the observer is given at least a 100msec exposure to target
3. time between OD&OS stimulation must be less than 100ms to keep stereoacuity

Front 22

how does CONTRAST affect stereoacuity

Back 22

1. extremely LOW contrast=elevated threshold

as contrast increases, stereoacuity improves rapidly

Front 23

how does COLOR affect stereoacuity

Back 23

1. threshold worse for blue targets than red/green targets
2. blue cones have less resolution and lower contrast sensitivity than red/green cones

Front 24

how does TARGET SEPARATION affect stereoacuity

Back 24

1. ~15-50 arcmin, BEST STEREOACUITY
2. >50 arcmin, THRESHOLD ELEVATED
3. <15 arcmin, THRESHOLD ELEVATED

Front 25

how does STIMULUS LOCATION affect stereoacuity

Back 25

Stereoscopic depth thresholds rise as a function of the degree of deviation from the horopter

Front 26

how does PRACTICE affect stereoacuity

Back 26

1. improves with practice
2. improvement may be spatially localized

Front 27

how does LATERAL MOTION affect stereoacuity

Back 27

1. stereoacuity remains unimpaired if lateral retinal image motion is of less than 2-3 deg/sec
2. microsaccades and drifting eye movements during fixation DOES NOT degrade stereoactuity
3. BETTER WITH NATURAL FIXATION than with stabilized retinal images

Front 28

STEREOMOTION

Back 28

1. we are NOT sensitive to stereomotion

Front 29

what is patent stereopsis

Back 29

QUANTITATIVE
1. within and slightly beyond Panum's fusional ranges
2. Both direction and magnitude of depth differences can be accurately perceived
3. degree of perceived depth is directly proportional to the magnitude of binocular disparity

Front 30

what is latent stereopsis

Back 30

from a range of DIPLOPIC disparities within which the DIRECTION, but NOT the magnitude, of depth differences can be accurately perceived

Front 31

what are stereograms

Back 31

1. two flat, 2D obj are presented to each eye independently
2. each of the 2 images mimic the effect of having two eyes separated by an IPD
3. the complete figures viewed binocularly are called STEREOGRAMS

Front 32

what are the TWO methods of displaying stereoscopic images

Back 32

1. STEREOSCOPIC HALF-VIEW:
the target independently presented to one eye.

2. STEREO PAIR:
two stereoscopic half-views, one of which is presented to the right eye and one to the left eye.

Front 33

anaglyphs

Back 33

Objects of complementary colors are viewed through colored filters to obtain independent control of the binocular objects

Front 34

vectograms

Back 34

1. polarized half views, one view polarized 90 deg away from the other eye
2. polarized glasses are used

TITMUS STEREO TEST

Front 35

autostereograms

Back 35

1. monocular views for BOTH eyes are contained in the same figure as repeated patterns
2. dependent on convergence of observer and which of the patterns are fused

Front 36

wallpaper illusion

Back 36

Convergence brings a new set of potential matching features into retinal correspondence near the fixation plane

Front 37

what are the classes of stereoscopic targets

Back 37

1. line or contour stereograms
2. stereogram with stimulus which is invisible monocularly but visible by means of the disparity-processing mechanism

Front 38

what is the mechanism for LOCAL STEREOPSIS

Back 38

1. no ambiguity about corresponding contours
2. disparity of contours in one region is processed without reference to disparities in other regions
3. similar points in the two monocular images are matched, and each locus is then assigned a disparity to elicit stereopsis

Front 39

what is the mechanism for GLOBAL STEREOPSIS

Back 39

1. ambiguities in the correct correspondence of retinal images
2. each matching pair of dots that provide the stimulus for stereopsis must be taken into account
3. Large areas of the binocular view are matched by finding patches with similar disparity and combining them to see an overall shape in depth

Front 40

difference between contour and RDS

Back 40

contour:
1. monocular contours
2. ONLY requires local stereopsis

RDS:
1. NO MONOCULAR CONTOURS
2. requires BOTH local and global stereopsis
3. takes longer time to perceive depth. decrease time with practice

Front 41

compare fine vs. coarse stereopsis

Back 41

FINE STEREOPSIS operates with SMALL retinal disparities, and stationary or slowly moving targets. It is supported by the PARVOCELLULAR system.

COARSE STEREOPSIS mainly operates with LARGER retinal disparities, and moving targets. It is supported by the MAGNOCELLULAR system.

Front 42

compare central v.s peripheral stereopsis

Back 42

Central:
1. +/- 0.5 deg at the fovea
2. detection of small disparities at fixation point

Peripheral
1. +/- 7-10 deg
2. selective for large disparities

peripheral stereopsis may still be intact when central stereopsis is absent

Front 43

disparity processing

Back 43

THREE DISPARITY CHANNELS
1. broadly tuned for either ZERO, CROSSED or UNCROSSED
2. observers with otherwise normal vision may exhibit stereoblindness for:
-crossed
-uncrossed
-disparity direction

Front 44

what are the layers in the LGN

Back 44

1. top four PARVOCELLULAR (3-6), input from midget ganglion cells
2. bottom two MAGNOCELLULAR (1-2) input from parasol ganglion cells
3. IPSILATERAL inputs sent to layer 2,3,&5
4. CONTRALATERAL inputs sent to layers 1,4,&6

Front 45

at what level of the visual system is binocularity present

Back 45

1. V1 Striate Cortex
2. Binocular neurons are found in layers outside layer IVC

Front 46

where is ocular dominance columns most distinct

Back 46

1. layer IVC
2. neurons within an ODC demonstrate the same eye preference

Front 47

processing of stereopsis along the vertical midline

Back 47

1. nasotemporal overlap from the midline region of each retina supports FINE stereopsis
2. fibers crossing in the corpus callosum supports COARSE stereopsis

Front 48

what happens at the chiasm with Ocular Albinism

Back 48

1. part of the TEMPORAL retina crosses at the chiasm and projects to the CONTRALATERAL hemisphere
2. can result in strabismus, loss of stereopsis