Intro To Binocular Vision Exam 2

Front 1

what are the components of horizontal vergence

Back 1

1. accommodative
2. fusional (disparity)
3. tonic
4. proximal
5. voluntary

Front 2

accommodative vergence

Back 2

1. provides gross adjustment of the position of the eyes
2. exerting a certain amount of accommodation elicits a determined amount of convergence

Front 3

fusional vergence

Back 3

1. fine adjustment of the visual axes to ensure binocular fixation
2. the stimulus eliciting the reflex is DISPARATE RETINAL IMAGERY

Front 4

tonic vergence

Back 4

movement that bring the eyes from anatomical position of rest into the physiologic position of rest

Front 5

proximal vergence

Back 5

stimulated by the perceived distance to a near object

Front 6

voluntary vergence

Back 6

1. vergence that a subject can apply consciously without an external stimulus
2. vision therapy

Front 7

what is the horopter

Back 7

the locus of all object points in physical space that are imaged on corresponding retinal elements at a given fixation distance

Front 8

why is the horopter visually significant

Back 8

1. reference point throughout visual field with the same disparity as at the fixation point
2. center of the range of single binocular vision where fusion is easiest
3. region of highest stereoscopic acuity where depth discrimination is the best

Front 9

what are the criteria for measuring the horopter

Back 9

1. identical visual directions
2. apparent frontoparallel plane
3. singleness (haplopia)
4. maximum stereoacuity
5. zero vergence

Front 10

identical visual direction horopter

Back 10

1. also called NONIUS HOROPTER
2. objects that stimulate corresponding points will be perceived as having the same visual direction in each eye
3. tested with non fusible targets

Front 11

apparent frontoparallel plane horopter

Back 11

1. if objects on horopter were defined by flatness or no stereoscopic depth, the horopter is obtained by moving stimulus objects to appear on a flat surface passing through the fixation point
2. easiest method to do for untrained subjects
3. subject fixates on middle rod
4. adjusts the depth of objects at different retinal eccentricities until they appear to lie to a flat plane parallel to the viewers face

Front 12

what is the singleness horopter

Back 12

1. any object that stimulates a pair of corresponding points: stimulates sensory fusion and be perceived to be single
2. measures extent of Panums Fusional Area

Front 13

how do you test for singleness horopter

Back 13

1. fixate at central rod
2. move test rod closer to the subject until diplopic, then move away from subject until diplopic
3. center of this zone is the singleness horopter

Front 14

where do you have maximum stereo acuity

Back 14

the finest stereoacuity for any location in the visual field is achieved when the reference stimulus is on the HOROPTER

Front 15

how do you test for maximum stereoacuity

Back 15

1. fixate at the central rod
2. place test rod lateral to fixation rod
3. for varios starting rod distances, stereoscopic threshold is measured as the minimum rod displacement needed to see a change in depth
4. for each eccentricity, the starting location of the rod that results in maximum stereoacuity is on the HOROPTER

Front 16

horopter based on zero vergence

Back 16

1. any object that stimulates a pair of corresponding points has ZERO DISPARITY
2. it does NOT stimulate a reflexive motor vergence response when introduced into the field of view

Front 17

how do you test for zero vergence horopter

Back 17

1. viewer wears eye movement measurement device
2. viewer fixates at the central rod
3. test rod flashes
4. if the flash target is on the horopter there will be NO reflexive vergence eye movement
5. test rod flashed at different eccentricities to map horopter

Front 18

what is hering-hillebrand deviation

Back 18

1. the change in curvature of the empirical horopter from the geometric horopter
2. the empirical horopter curve is slightly FLATTER than Vieth-Muller circle when fixating at a NEAR OBJECT

Front 19

what is nasal-temporal asymmetries

Back 19

the perception of equal visual angles requires a longer nasal retinal distance than temporal retinal distance

Front 20

what is the abathic distance

Back 20

distance at which the horopter curvature is flat

Front 21

curvature related to abathic distance

Back 21

1. NEAR FIXATION, the horopter is CONCAVE towards the observer
2. DISTANCE FIXATION greater than the abathic distance, the curvature is CONVEX

Front 22

what are the factors affecting the slant of empirical horopter

Back 22

OPTICAL DISTORTION
1. magnification difference between the two eyes (aniseikonia)

example: horizontal magnification of OD image causes ROTATION of the horopter TOWARDS the OD

Front 23

what are the factors that affect the location of empirical horopter

Back 23

FIXATION DISPARITY
1. residual fixation error during binocular viewing conditions (caused by small vergence inaccuracy)
2. location of the empirical horopter is displaced from the fixation point in the direction of fixation disparity

Front 24

what is the significance of H in the horopter equation

Back 24

the deviation of the horopter curvature from the curvature of VM circle

1. H=0 (ON VM circle)
2. H>0 (less concave than VM circle)
3. H<0 (more concave than VM circle)

Front 25

what is the significance of Ro in the horopter equation

Back 25

the ratio of horizontal magnification between the two eyes measured at the fixation point

1. R>1 (rotated towards the LEFT eye
2. R=1 (NO SLANT)
3. R<1 (rotated towards the RIGHT eye)

Front 26

what are the characteristics of a vertical horopter

Back 26

1. theoretical vertical line in the median plane running through the fixation point
2. empirical v. horopter exhibits a backwards inclination with top away from and the bottom towards the observer
3. more inclined with DISTANCE, less inclined with NEAR

Front 27

what does the horopter look like with strabismic patients

Back 27

exotropia:
1. horopter shows excessive concavity
2. may lie within VM circle

esotropia:
1. horopter shows localized central convexity toward the eye (FLOM NOTCH)

Front 28

what is horror fusionis

Back 28

1. avoidance of binocular fusion
2. symptoms: diplopia that cannot by eliminated with prism
3. acquired disruption of central fusion

Front 29

what are the two causes of Aniseikonia

Back 29

optical factors:
1. optics of the eye (uncorrected axial anisometropia)
2. optical correction by unequal lenses

Neural factors
1. cause PERCEIVED difference in size/shape although the retinal images in the two eyes of the same object have the same size/shape
2. alteration of retinal photoreceptor distributions in the two eyes

Front 30

how much aniseikonia well be present when patient starts to exhibit symptoms

Back 30

1. 1-2% can cause asthenopia
2. >5% elevates stereoscopic thresholds
3. >20% prevents fusion

Front 31

what are the two types of uniform magnifications

Back 31

1. overall magnification
-mag. equal in all directions
-spherical correction

2. meridional magnification
-mag in one one meridian
-x090 horizontal mag.
-x180 vertical mag.

Front 32

what is non-uniform magnfication

Back 32

1. prismatic magnification
greater mag at apex of prism than at base

Front 33

what is the GEOMETRIC EFFECT of optical magnification

Back 33

1. visual space distortion caused by magnification of retinal image in one eye in the horizontal meridian
2. spatial distortion is explained by the lateral binocular disparities resulting from unequal retinal image sizes
3. greater horizontal mag. of one eye's retinal image causes the horopter to rotate TOWARDS this eye

Front 34

what is the INDUCED EFFECT of optical magnification

Back 34

1. visual space distortion caused by magnification of retinal image in one eye in the vertical meridian (x180 mag)
2. greater vertical mag of one eye's retinal image causes the horopter to rotate AWAY from this eye
3. occurs for relatively small amounts of mag
4. stops at mag >5-7%

Front 35

what happens when the overall monocular magnification is LESS than 5-7%

Back 35

1. cancellation of geometric effect by induced effect
2. little binocular spatial distortion

Front 36

what happens when the overall monocular magnification is MORE than 5-7%

Back 36

1. geometric effect is dominant
-rotation of perceived frontoparallel plane AWAY from the magnified eye
-rotatioin of horopter TOWARD the magnified eye

Front 37

what causes an UPWARD DIVERGENT anseikonia

Back 37

Upward:
1. upper portion of a plane to appear ENLARGED and tilted AWAY
2. OS Mag @ 045
3. OD Mag @ 135

Front 38

what causes an DOWNWARD DIVERGENT anseikonia

Back 38

Downward:
1. upper portions of a plane to appear SMALLER and tilted TOWARDS observer
2. OS Mag @ 135
3. OD Mag @ 045

Front 39

what is the source of oblique magnifications

Back 39

1. cylindrical refractive lenses at oblique axes
2. cyclorotary eye movements
-cyclovergence eye movements can partially compensate for oblique magnification from other sources

Front 40

what is the prismatic effect of a patient with BASE OUT prism

Back 40

1. perceived space curves more concave relative to observer
2. horopter curves more convex relative to observer

Front 41

what is the prismatic effect of a patient with BASE IN prism

Back 41

1. perceived space curves more convex relative to observer
2. horopter curves more concave relative to observer

Front 42

READ OVER TESTING FOR ANISEIKONIA

Back 42

READ OVER TESTING FOR ANISEIKONIA

Front 43

how long does it take for adaptation to induced aniseikonia to occur

Back 43

1. short term adaptation begin in about 20min
-requires interaction with a natural visual environment and motor feedback
2. maximum adaptation takes less than a week
-geometric: ~3-4days
-induced: ~5-6days
3. less adaptation to OBLIQUE mag.

Front 44

how does environmental conditions affect adaption to induced aniseikonia

Back 44

1. better adaptation occurs in free space and natural viewing conditions
2. effects can reappear in more restricted visual environments
3. sterescopic mechanisms do nto adapt to spatial distortion

Front 45

KNAPP'S LAW

Back 45

1. placing the second principal plane of a correcting lens coincident with the anterior focal point of an axial ametrope creates a retinal image size equal to that of an emmetrope
2. correct REFRACTIVE anisometropes with CONTACT LENSES
3. correct AXIAL anisometropes with KNAPPS LAW
4. Knapps Law ignores interocular differences in spatial scale common in most axial ametropes

Front 46

what does sensory fusion require

Back 46

requires that similar images be presented SIMULTANEOUSLY to corresponding points in the two eyes, or within Panum's fusional range

Front 47

when does binocular rivalry occur

Back 47

occurs when vastly dissimilar objects are imaged in the two eyes and subjective perception alternates between them

Front 48

what are the two forms of binocular rivalry

Back 48

EXCLUSIVE DOMINANCE
1. alternating suppression of the entire image
2. occurs when targets are SMALL in area

MOSAIC DOMINANCE:
1. changing regions of alternating suppression within the field of view
2. occurs when targets are LARGER in area

Front 49

what happens when you increase the strength of one eye's image in binocular rivalry

Back 49

1. increasing the strength of one eye's image relative to that of the other eye increases the PROPORTION of time during which it is perceptually dominant
2. the rate of perceptually alternation is not under voluntary control

Front 50

what is binocular luster

Back 50

when the contours are similar for each eye's image, but the images differ in LUMINANCE, COLOR, or have OPPOSITE CONTRAST SIGNS.

appears GLOSSY

Front 51

binocular luster in respects to fusing two separate colors

Back 51

1. the fused color appears to be a mixture of the monocular hues
2. the percept may be difficult to maintain and may alternate between the two colors
3. portions may contain the mixed color and other portions may contain one color or the other.
4. may also be observed using anaglyph glasses while looking at a white field

Front 52

what is Wolf and Blake's mechanism for Rivalry

Back 52

1. two monocular channels and one binocular channel
2. whenever possible the binocular channel is activated and fusion occurs
3. when not possible, the monocular channels alternately inhibit on another. As one monocular channel fatigues, the other one takes over.

Front 53

what is the mechanism for Rivalry in respects to INHIBITION

Back 53

1. reciprocal inhibition between monocular neurons before their convergence onto binocular neurons

stereopsis can occur in the presence of rivalry, but its weakened

Front 54

what is a clinical aspect of suppression

Back 54

1. monovision
2. one eye has distance Rx, and the other eye has near Rx
3. at any given fixation distance, the eye with the blurrier image is suppressed

Front 55

what is the relationship between suppression and sensitivity

Back 55

1. suppressed area shows a REDUCTION IN VISUAL SENSITIVITY
2. Elevation of light detection thresholds
3. Prolonged reaction times
4. May include part or all of the field of view of the suppressed eye

Front 56

what is the relationship between suppression and binocularity

Back 56

1. lack of contribution from one eye to the binocular perception
2. occurs during binocular viewing
3. although it occurs in one eye, its due to a binocular interaction

Front 57

what is the zone of suppression

Back 57

1. contours are dominant over blank fields. Thus, in the BINOCULAR percept the contour suppresses the corresponding uniform in the other eye
2. the zone of suppression extends over a small area beyond the contour itself

Front 58

zone of suppression in relation to spatial frequency

Back 58

the size of the zone of suppression decreases with increasing spatial frequency of the targets

Front 59

when does a halo of suppression occur

Back 59

1. where the image differs greatly
2. areas where local contours are similar can undergo binocular summation in the combined percept
3. intersection in combined percept is darker than in either monocular view

Front 60

what is da vinci stereopsis

Back 60

1. near occluding surface can occlude distant surfaces to different extent in the two eyes
2. the visual system makes use of the occlusive relations to recover the relative depths of the two surfaces

Front 61

suppression in strabismus

Back 61

DIPLOPIA
1. alternates between the two eyes. dominate eye wins
2. suppression in the deviating eye to avoid diplopia
3. in time causes amblyopia

Front 62

suppression in esotropia

Back 62

1. causes SCOTOMA
2. size of suppression scotoma is usually proportional to the obj. angle of deviation
3. larger scotoma is related to a greater decrease of stereoacuity

Front 63

what is a scotoma

Back 63

an area of suppression in the deviated eye commonly encompassing both the fovea and the nasal retinal point where the fixation object is imaged

Front 64

what form of strabismus has greater suppression

Back 64

ESOTROPIA
-because of greater magnitude of nasal imaging in the strabismic eye

Front 65

suppression in exotropia

Back 65

1. not as bad as esotropia, but extends over a wider area
2. includes fovea and entire temporal hemisphere of bad eye
3. more often intermittent than in esotropia. (occurs only during deviation)

Front 66

what happens to the suppression in an alternating strabismic

Back 66

in alternating exotrope (or esotrope), suppression also alternates

Front 67

what is the binocular/monocular contrast sensitivity ratio

Back 67

ratio: 1.4

1. that means that BINOCULAR contrast sensitivity is better.
2. ratio is sensitivity ratio is CONSTANT regardless of spatial freq.

Front 68

what is the independence theory

Back 68

1. probability summation (with independent sampling)
2. due to each eye's independent chance of detecting a stimulus which causes better overall performance than if only a single eye is tested
3. can occur with stimuli at non corresponding points in the two eyes

Front 69

suppression in strabismus

Back 69

DIPLOPIA
1. alternates between the two eyes. dominate eye wins
2. suppression in the deviating eye to avoid diplopia
3. in time causes amblyopia

Front 70

suppression in esotropia

Back 70

1. causes SCOTOMA
2. size of suppression scotoma is usually proportional to the obj. angle of deviation
3. larger scotoma is related to a greater decrease of stereoacuity

Front 71

what is a scotoma

Back 71

an area of suppression in the deviated eye commonly encompassing both the fovea and the nasal retinal point where the fixation object is imaged

Front 72

what form of strabismus has greater suppression

Back 72

ESOTROPIA
-because of greater magnitude of nasal imaging in the strabismic eye

Front 73

suppression in exotropia

Back 73

1. not as bad as esotropia, but extends over a wider area
2. includes fovea and entire temporal hemisphere of bad eye
3. more often intermittent than in esotropia. (occurs only during deviation)

Front 74

what happens to the suppression in an alternating strabismic

Back 74

in alternating exotrope (or esotrope), suppression also alternates

Front 75

what is the binocular/monocular contrast sensitivity ratio

Back 75

ratio: 1.4

1. that means that BINOCULAR contrast sensitivity is better.
2. ratio is sensitivity ratio is CONSTANT regardless of spatial freq.

Front 76

what is the independence theory

Back 76

1. probability summation (with independent sampling)
2. due to each eye's independent chance of detecting a stimulus which causes better overall performance than if only a single eye is tested
3. can occur with stimuli at non corresponding points in the two eyes

Front 77

what is Fechner's Paradox

Back 77

1. if the retinal illuminance of a suprathreshold light differs between the two eyes, its perceived brightness will correspond to the AVERAGE of the two retinal illuminances
2. the light will appear LESS BRIGHT when viewed binocularly than if viewed the eye with the higher retinal illumninance.

Front 78

for binocular brightness averaging what is the INDEPENDENCE HYPOTHESIS

Back 78

binocular brightness would be the same as the brightness perceived by the eye with the greater retinal illuminance viewing alone

Front 79

for binocular brightness averaging what is the SUMMATION HYPOTHESIS

Back 79

binocular brightness should be greater than the brightness perceived by the eye with the greater retinal illuminance viewing alone

Front 80

what THREE effects elicit interocular transfer

Back 80

1. motion aftereffect
2. orientation (tilt) aftereffect
3. spatial frequency (size) aftereffect

*depends upon binocular neurons at the level of V1 or higher

Front 81

what is dichoptic masking

Back 81

degradation of the perception of a test stimulus presented to one eye due to the presentation of a masking stimulus to the other eye

effect of the mask is stronger when its presented to the dominant eye