Binocular Correspondence

Question 1

what is hering’s 2nd law of visual direction

Answer 1

there is a retinal point to point relationship between the 2 eyes
-for every retinal point in one eye there is a corresponding retinal point in the fellow eye w/ an identical sense of visual direction

Question 2

what is hering’s 3rd law

Answer 2

objects on the visual axis of either eye in symmetrical convergence appear to be on the median plane of the head (straight ahead)

Question 3

what is a cyclopean direction

Answer 3

a single visual direction in the binocular visual field

Question 4

binocular egocentric direction = ___+_____

Answer 4

cyclopean direction+gaze registration

Question 5

cyclopean directions are analagous to…

Answer 5

oculocentric direction

Question 6

all points on the retina have a binocular corresponding point except…

Answer 6

at the optic nerve head

Question 7

normal correspondence only dpends on the retinal points being stimulated and is nnot affected by…

Answer 7

image luminance 
contrast
color
size
orientation

Question 8

normal correspondence is very stable, altered by …

Answer 8

only a few minutes of arc in the foveas, and then only by extreme fusional stress

Question 9

what is spatial correspondnce a property of

Answer 9

the brain

also evident in the somatosensory system

Question 10

what is binocular disparity

Answer 10

stimulation of noncorresponding points

Question 11

each pair of corresponding oculocenric directions form a single….

Answer 11

cyclopean direction

Question 12

what is a single visual direction in the binocular visual field

Answer 12

cylclopean direction

Question 13

what are some synonyms of binocular disparity

Answer 13

retinal disparity

physiological disparity

Question 14

what can crossed disparities stimulate

Answer 14

1. steroscropic “nearness” if not a large amount of disparity
2. crossed diplopia from disparity too large
3. ocular convergence can be stimulated to look at the near object

Question 15

what can uncrossed disparity stimulate

Answer 15

1. stereoscopic “farness” if disparity small enough
2. uncrossed diplopia disparity too large
3. ocular divergnce to look at far object

Question 16

what is the horopter

Answer 16

the set of points in physical space that can stimulate corresponding retinal points when eyes are converged to aim at a fixation point

Question 17

how is the horopter shaped

Answer 17

bowl-shaped surface in near vision and flattens out as you look farther away

Question 18

what is the best at the horopter

Answer 18

stereopsis and binocular summation

-single vision also occurs here

Question 19

what is the veith-muller circle (VMO)

what question does it answer

Answer 19

theoretical horopter

“in principle, where should you put lights in physical space to stimulate corresponding points”

Question 20

what does the VMO assume

Answer 20

eyes are identical and optically undisorted

Question 21

what do objects in the VMo stimulate

Answer 21

zero binocular disparity

Question 22

waht can objects in the peripheral vision stimulate

Answer 22

cross disparity
zero disparity
uncrossed disparity

Question 23

where are the images for crossed disparity

where is it in relation to the VMO

Answer 23

images are more temporalward on the retinas, relative to corresponding opints
-inside the VMO

Question 24

where are the images for uncrossed disparity

where is it in relation to the VMO

Answer 24

images are more nasalward on the retinas, relavtive to correspoinding points
-outside the VMO

Question 25

what is the empirical horopter

Answer 25

answering the question "where do i have to put lights in physical space to stimulate corresponding points in this person"

Question 26

what direction do we measure the horopter

Answer 26

horiztonal (longtidinal) direction

Question 27

what are the additional rod adjustment criteria that measure an approximate horopter

Answer 27

``` apparent fronto-parallel plane equal distance haplopia max stereo actuity zero vergence ```

Question 28

which methods of measuring the horopter don't reflect the effects of fixation disparity

Answer 28

apparent fronto-parallel plane | equal distance

Question 29

which method of measuring the horopter measures the extent of panum's area

Answer 29

haplopia "single vision"

Question 30

what will non zero vergence make you use to see an object

Answer 30

vergence eye movement

Question 31

how does maximum stereoscopic acuity work

Answer 31

finer the stereoscropic threshold, the closer a point is in space to the horopter

Question 32

what results does the spatial plot of the horopter show

Answer 32

ELH results

Question 33

what are the 3 variables to quantify the ELH

Answer 33

relative curvature (hering-hillebrand deviation) skew (horopter closer to right or left) offset (how far off the fixation plane is the horopter displaced)

Question 34

does the normal horopter have more or less curvature than the VMO

Answer 34

normal has less than VMO bc of the asymmetry of the eye

Question 35

how do wedge prisms bend stereoscropic space

Answer 35

creates disparity where there shouldnt be any

Question 36

what does a large BO prism make a flat surface appear as? | what does a large BI prism do?

Answer 36

BO=concave (convex horopter) | BI=convex (concave horopter)

Question 37

is the ELH or the VMO more curved in a divergence excess intermittent exotropia - why is divergence stimulated - uncrossed or crossed disparity?

Answer 37

ELH more curved than VMO in near vision (only known conidition w/ this type of ELH) - most objects don't fall on this horopter so stimulates divergecne (most of them are beyond this ELH) - uncrossed disparities in near fixation may result in their tendency to diverge

Question 38

what is skew a product of

Answer 38

horizontal aniseikonia

Question 39

what are small offsets caused by

Answer 39

fixation disparity (FD)

Question 40

waht does FD cause eyes to do

Answer 40

misconverge during bifxiation

Question 41

does FD disrupt fusion? | what does it reduce?

Answer 41

too small to disrupt fusion | steropsis may be reduced

Question 42

what is it called when the eyes converge too much | when the eyes converge not enough

Answer 42

too much = eso | too little = exo

Question 43

what are large offsets caused by | what is lost in a large offset

Answer 43

strabismus | central steropsis is lost

Question 44

what condition can cuase the horopter to have a small notch in it -what is the notch called

Answer 44

esotropic strabismus | -flom notch

Question 45

what is the definition of anomalous retinal correspondence (ARC)

Answer 45

- the centers of the foveas have diff visual directions | - the fovea of one eye has the same visual direction as a peripheral retinal point in the fellow eye

Question 46

when does ARC only occur in

Answer 46

early-onset strabismus - congenital OR - acquired (very early age)

Question 47

how can arc be a good predictor in the treatment of esotropia

Answer 47

arc present = less than 50% chance of cure arc absent=better than 50% chance of cure -arc prevents reflexive movements

Question 48

in testing correspondence, the purpose is...

Answer 48

to show whether correspondence is bifoveal

Question 49

when will there be correspondence

Answer 49

when both eyes are being used

Question 50

what is testing ARC based on

Answer 50

visual direction judgements

Question 51

when does ARC sometimes disappear

Answer 51

in total darkness

Question 52

why does it not work if we test correspondence based on fusion? stereopsis?

Answer 52

patient still may be able to fuse if non correscpoinding points are stimulated -same with stereopsis, patients with arc may present w/ normal stereo

Question 53

how must the test targets be in testing correspondence

Answer 53

the test targets for both eyes must be unfusible but simultaneously visible (so we can assure that we are testing the visual directions of each eye) -ned patient to see 2 images at the same time

Question 54

what can void a correspondence test

Answer 54

image suppression or fusion

Question 55

how can you make the od and os test images unfusible

Answer 55

spatial separation time separation form separation

Question 56

what is spatial separation

Answer 56

- use polaroid glasses and pol target so each eye sees one image, keep background fusible - large vertical disparity maintains dissociation (od image above where they are looking, os image below) - horizontal directions are compared - not often used in clinic

Question 57

what is time separation | when can this be used

Answer 57

- flicker the image to the right eye then to the lef teye - pt can't fuse the images but can still compare the direction - used in "major amblyoscope"

Question 58

what is form separation | when can this be used

Answer 58

- 2 image shapes are so diff they can't be fused - used in afterimage test (horiz in one eye and vert in other, can compare direction of each image) and bagolini lens test (diff orientation in each eye, can't fuse but cna compare their visual direction)

Question 59

what are the 2 questions you must ask to diagnose ARC

Answer 59

1. where did the patient see the 2 targets? - subjective - comparison of the visual directions btwn the 2 eyes 2. where were the images on the retina? - are they both on fovea? - stimulate foveas monocullary to ensure this

Question 60

what is the afterimage test

Answer 60

- monocularly place afterimage on each fovea - open both eyes - assess visual directions: cross=foveas have same visual direction and are corres points, no ARC

Question 61

if a vertical line was on the left eye and a horiz line on the right eye, what would a pt with a left esotrope w/ ARC see

Answer 61

horiz line to the left and vertical line to the right (crossed diplopia) - bc the fovea of the left eye is temporal to the retinal point that is corresponding w/ the fovea of the straight eye - afterimage is temporal to the point being used to see "straight ahead" so it will appear in the nasal field

Question 62

if a ptient is strabismic with arc, what would they see with the bagolini lens

Answer 62

2 lines form a symmetric cross

Question 63

what would a ptient with strabismus but no arc see with a bagolini lens

Answer 63

2 lines that are not overlapping

Question 64

if the patient has a left esotropia what will they see with the bagolini lens

Answer 64

bulb and streak stimulate a nasal point on the left eye - fovea stim in the right eye - left eye will see the image in the temporal field = uncrossed dipolpia - botton streaks, no top

Question 65

what is the zero measure point

Answer 65

the peripheral retinal point that the fixation target image falls on on the turned eye

Question 66

what is the pseudofovea (pf)

Answer 66

the PVD moves from the fovea to a point closer to the zero-measure point in the turned eye

Question 67

in a normal left esotropic eye w/o arc, where would the patient see the image of the target

Answer 67

to their left w/ their left eye | -uncrossed dipolopia

Question 68

what will the patient see if the pseudofovea lies on the zero measure point

Answer 68

single

Question 69

how are ef and pf related

Answer 69

they both use a point other than the fovea as the PVD - they are measured separtately bc the brain rewires these btwn binocular and monocular vision - may be diff than the

Question 70

when the pseudofovea is shifted from the physiological fovea, all other local signs...

Answer 70

shift with it. in the same direction and by the same amount

Question 71

a patient with arc will have a psuedofovea that is closer to the zero measure point, what does this result in

Answer 71

smaller amount of disparity, smaler amount of diplopia | -img on the zero ref point seems to be closer to the straight ahead position

Question 72

a patient w/o arc but with the same amount of eye turn of patient w/ arc will use what as their pvd waht does this mean

Answer 72

fovea => thus the fixation image will be stimulated a point far from the fovea => larger diplopia

Question 73

the displacement of the psuedofovea correlates with the size of...

Answer 73

the strabismus

Question 74

why can permanent diplopia occur after strab correction surgery

Answer 74

patinet is still using arc -when the ey was turned this accounted for it but now it has a straight eye and the visual directions btwn the eyes are confused

Question 75

what are the 3 types of arc

Answer 75

harmonious: single; pf at zero measure point. unharmonious: uncrossed diplopia=eso, crossed=exo; pf btwn the fovea and zero meausre point paradoxical: crossed=eso, uncrossed=exo; pf more than the amount of eye turn

Question 76

how many prism dioptoers is arc considered

Answer 76

20 prism diopters

Question 77

what is burian's sensory theory of arc (most widely accepted)

Answer 77

arc is a sensory adaptation to constant strabismus - deviated local signs are remapped in visual cortex (develops slowly throughout early childhood) - do not lose normal corres completely - arc can be turned on and off once established

Question 78

what is morgan's motor theory of arc

Answer 78

arc is the result of the registration of the abnormal motor innervation that causes strab

Question 79

what can morgan's motor theory predict | what can it not easily explain

Answer 79

harmonious arc-no fusion or stereo bc the points on the retina do not agree nonuniform arm

Question 80

how does the motor theory best explain covariation

Answer 80

as the amount of the eye turn decreases, the amount of arc should decrease as well. the amount of arc depends directly on the motor innervations of the eye muscles and the amount of eye turn