5. Binocular and Spatial Vision - Eye Movements & Binocular Vision Summer 2026

1) Utrocular

2) Ambicular

Two-eyed vertebrate vision comes in 2 varieties. What are these?

2 eyes function separately

What is the meaning of utrocular?

2 eyes work together (true binocular vision)

What is the meaning of ambiocular?

the coordinated behavior of the 2 eyes in the perception of space

What is binocular vision?

independent

With utrocular vision, eye movements are _________

complete crossing

With utrocular vision, there is ______ of the optic nerves

lower vertebrates

What types of animals have utrocular vision?

coordinated (Hering's Law of Equal Innervation)

With ambiocular vision, eye movements are _________

partial decussation -- at the optic chiasm

With ambiocular vision, there is ______ of the optic nerves

mammals

What types of animals have ambiocular vision?

Optic Nerve Types -- Complete Decussation and Partial Decussation (Pic)

Optic Nerve Types -- Complete Decussation and Partial Decussation (Pic)

No -- eye movements are independent. Vision calculated FOR EACH EYE.

Is this animal strabismic?

Utrocular Eye Movements (Pic)

Utrocular Eye Movements (Pic)

No

Do utrocular eye movements follow Hering's Law of Equal Innervation?

ambiocular vision

Frontal eyes facilitate what?

No

Are frontal eyes required for ambiocular vision?

lateral -- provide safety through panoramic view

Prey animals usually have (lateral/frontal) eyes. Why?

frontal -- provide better depth perception and visual acuity for offensive behavior

Predator animals usually have (lateral/frontal) eyes. Why?

Binocular Visual Fields -- Horse and Primate (Pic)

Binocular Visual Fields -- Horse and Primate (Pic)

Yes

Can a rabbit see 360º around its body?

Angle between optic axis (with the eye centered in orbit) and the body midline

What is ocular laterality?

angle between the line of fixation and the optic axis

What is angle γ when talking about binocular vision?

nasal-temporal

There is a _____ division in ambiocular vision

NO

In an animal with a larger angle γ, are the optics (VA) good in the periphery?

-for stereopsis

-for better VA

Why is ambiocular vision important?

the specific sensation of depth characteristic of ambiocular vision

What is stereopsis?

coordinated eye movements and retinal correspondence

Stereopsis is made possible by what?

since frontal eyes have a smaller angle γ they have better optics

Why does ambiocular vision lead to better visual acuity?

independent

With utrocular vision, the visual directions derived from the 2 eyes are _______

oculocentric direction

With ambiocular vision, the foveas are assigned a common _________

Hering's Law of Identical Visual Directions

With ambiocular vision, what Law applies?

Yes

Are the foveas in ambiocular vision corresponding points?

confusion

overlap of dissimilar objects

Bifoveal fixation

______ is necessary to avoid confusion

single

If βR = βL, the star object will also be seen as ______

-depth perception

-brightness perception

-light adaptation

-light detection threshold

How does monocular vision differ from binocular vision in humans?

Comparison of Normal Thresholds of Monocular and Binocular Depth Perception at a Distance of 1m (Pic)

Comparison of Normal Thresholds of Monocular and Binocular Depth Perception at a Distance of 1m (Pic)

10

Depth Perception is ___x stronger binocularly at near distances

false -- brightness viewing with both eyes is normally the same as with one eye

True or False:

Brightness viewing with both eyes is normally brighter than viewing with one eye only

the luminances of the 2 eyes are the avg NOT the sum of the luminances between the eyes

Why is brightness viewing with both eyes normally the same as with one eye?

true

True or False:

The eyes dark adapt independently of each other

Patching one eye will allow that eye to dark adapt without affecting the other eye

What is an example of dark adapting one eye only?

75%

What is the probability of seeing with 2 eyes?

-ocular or eye direction (α)

-oculocentric or relative direction (B)

-egocentric or absolute direction (χ)

What are the direction specifications?

+

Sign Convention for Directions

Right

-

Sign Convention for Directions

Left

+

Sign Convention for Directions

Up

-

Sign Convention for Directions

Down

require the eye to rotate more than the normal amount

The prismatic effects of plus lenses will require the eye to do what?

image, eye

Prism will move the ____ not the ____

pastpointing

When patient is wearing plus lenses, _____ is possible

require the eye to rotate less than the normal amount

The prismatic effects of minus lenses will require the eye to do what?

true

True or False:

Patients will adapt their limb proprioception to match vision

matrixes

Over time, patients can have two separate _____ if they switch from glasses to CLs often

TBI patients whose visual adaptation is poor

Switching from glasses to CLs is disorienting for what patients?

Yes

Are bifocals disorienting for TBI patients whose visual adaptation is poor?

-ocular

-oculocentric

-egocentric

Types of Binocular Direction

1) Dominant Eye Theory

2) Cuclopean Theory

How are ocular directions (αR and αL) from each eye combined in binocular vision?

Direction is that of the dominant eye (αR OR αL)

What is the dominant eye theory of binocular ocular direction?

The direction is the avg of the 2 eyes (αR + αL) / 2

What is the Cyclopean Theory of binocular ocular direction?

Binocular Ocular Direction -- Combining aR and αL (Pic)

Binocular Ocular Direction -- Combining aR and αL (Pic)

1) Dominant Eye Theory

2) Cyclopean Theory

How are oculocentric directions (βR and βL) combined in binocular vision?

Either βR or βL is suppressed and direction is given by the other

What is the dominant eye theory of binocular oculocentric direction?

βR and βL are averaged

What is the Cyclopean theory of binocular oculocentric direction?

1) Dominant Eye Theory

2) Cyclopean Theory

How is egocentric information (a + β) for each eye combined in binocular vision?

either (αL + βL) or (αR + βR)

What is the dominant eye theory of binocular egocentric direction?

Ego = (αL + βL) + (aR + βR) / 2

What is the Cyclopean theory of binocular egocentric direction?

true

True or False:

A minus lens or a prism in front of just ONE EYE will influence egocentric direction

will

A minus lens or a prism before JUST ONE EYE, (will/will not) influence the egocentric direction of the target

Yes -- moves to the left no matter which eye you put it in front of

If BR prism is placed in front of ONE EYE, will the target appear to move binocularly?

the body reference point for egocentric direction

What is the egocenter?

-dominant eye theory states egocenter is at the dominant eye (COR)

-cyclopean theory states egocenter is midway between the eyes

What is the location of the egocenter?

mark points between fixated objects and your perceived location

-repeat process at different viewing angles

Method to Find the Egocenter?

egocenter is between the eyes but about 10cm behind the plane of the eyees (above the foramen magnum)

What is the result of finding the egocenter?

axis of rotation of the head

What is the dens?

corresponding points

Retinal points, one in each eye, having the same oculocentric direction

Yes -- βR and βL are corresponding points

Are there oculocentric directions for EACH EYE?

When βR = βL

Theoretically, when do corresponding points occur?

correspondence (Hering's Law of Identical Visual Directions)

What does Hering's Window illustrate?

on a spot on the window

Where is fixation at with Hering's window?

same location (confusion)

The tree and house will appear in the _______ with Hering's window

diplopia

_____ is present in Hering's window because the tree DOES NOT fall on corresponding points for the two eyes

Bifoveal fixation

_____ of the tree will cause normal binocular vision and in its proper location

single as well

If the images of the house fall on another pair of corresponding points, how do we perceive the house?

tree

When patient has a R esotropia, the ____ is not fixated by the deviating R eye

No -- perceived locations will be wrong and confusion will present

When patient has a R esotropia, will the perceived locations of the tree and house be correct?

yes

When patient has a R esotropia, will diplopia be present?

left fovea will correspond to a point on nasal retina of the right eye

For a patient with right esotropia, what happens when anomalous retinal correspondence occurs?

harmonious anomalous retinal correspondence

If ARC EXACTLY superimposes the target for both eyes... what is this called?

nasally

With anomalous retinal correspondence with right esotropia, all corresponding points in right eye are shifted (nasally/temporally)

in proper locations

When a patient with a right esotropia develops anomalous retinal correspondence, targets will appear how?

confusion and diplopia

Anomalous retinal correspondence prevents what?

-Tree and house would be correctly localized by each eye

-Lack of correspondence is easily confused with harmonious ARC but they are different

If patient has UTROCULAR vision, what would be the appearance if there was NO correspondence?

corresponding retinal points

corresponding points are retinal positions, one in each eye, that have identical oculocentric directions

foveas

The _____ are corresponding points

βL = βR

_______ = _____ for all corresponding points

retinal or absolute disparity

Results from stimulation of non-corresponding retinla points

βL - βR

What is the equation for retinal disparity?

angular separation

The _____ of images in the two eyes is equal to the disparity

0

When βL = βR, then retinal disparity is ____