Procedures I - Intro to Binocular Vision

Binocular vision

The use of both eye simultaneously in such a manner that each retinal image contributes to the final percept

- Good Eye Health

- Integrity of Visual Structures

- Optimally Corrected Visual Acuity

Within the pyramid of vision, what is the most basic level of vision?

Visual Efficiency through binocularity

Within the pyramid of vision, what is the second level of vision?

- accommodation

- eye teaming

- eye tracking

Binocularity contributes to visual efficiency through what three things?

Visual Information Processing (VIP)

Within the pyramid of vision, what is the highest level of vision?

- single vision

- increases visual field

- blind spot compensation

- visual searching

- stereopsis

What are 5 advantages of binocularity?

- ability to move eyes to bifoveate

- clear images

- similar size/ shape/ luminance of the images of each eye

What are three requirements for stereopsis?

bifoveate

this refers to having the foveas of both eyes aimed at an object of regard

Motor function

Within binocularity this is how the eyes work together to provide input for sensory fusion

Sensory fusion

Within binocularity this is the final visual perception of single vision

- maintain bifoveal fixation

- prevent blur from retinal image motion

Within the motor function of binocularity, what are the two things that eye eyes must do ?

- ductions

- versions

- vergences

What are three functions that the eye can perform to maintain bifocal fixation?

13mm behind the cornea

Where is the center of rotation of the eye scientifically measured to be?

Supraduction

An upward rotation of the eye

infraduction

A downward rotation of the eye

Abduction

rotation of the eye away from the midline

Adduction

rotation of the eye toward the midline

Encyclotorsion

the medial rotation of the eye around the y-axis

Excyclotorsion

the lateral rotation of the eye around the y-axis

version movements

binocular movement of the eyes in the same directions

vergence movements

binocular movement of the eyes in opposite directions

Ductions

Monocular eye movements are referred to as what type of movements?

primary gaze

When considering versions, all movements of the eyes are relative to what position?

dextroversion

Both eyes move right

levoversion

Both eyes move left

supraversion

Both eyes move upward

infraversion

Both eyes move downward

Herring's Law

This law states that "in all voluntary conjugate movements of the eyes, equal and simultaneous innervation folds from the oculogyric centers to the muscles concerned in establishing the direction of gaze"

Sherrington's Law of Reciprocal Innervation

This law contributes to conjugate ocular movements "by a steady firing of nerve impulses to the agonist muscles and an accompanying reduction in firing to the antagonist muscles"

Saccades

fast eye movements to switch gaze from one object to another

Pursuits

eyes movement used to follow a moving object and keep it in focus

convergence

binocular movement in which both eyes adduct

divergence

binocular movement in which both eyes abduct

supra/infra vergence

binocular movement in which one eye moves up while the other moves down

Maddox classification

The types of vergences can be classified by what?

- tonic

- proximal

- accommodative

- fusional/disparity

What are the four types of vergence in Maddox classification?

tonic vergence

In terms of vergence this is the physiological position of the eyes at rest in the absence of any visual stimulus

EOM tone

tonic vergence is maintained by what?

Proximal vergence

Nearness of an object stimulates this type of convergence reflex, which is separate from the accommodative stimulus

accommodative vergence

type of vergence driven by the accommodation and blur

Fusional/Disparity

This type of vergence completes the vergence response for fusion/singularity

4 types of vergences

Total vergence is is found by taking the sum of what?

- vestibulo-ocular response (VOR)

- orthostatic reflex

- optokinetic nystagmus

To prevent blur due to retinal image motion, our eyes do what three functions/reflexes?

vestibulo-ocular response (VOR)

Coordination of motion information with visual information that allows you to maintain your gaze on an object while you move.

True

True or False: The vestibulo-ocular response is purely reflexive

head motion

The vestibulo-ocular response occurs as a result of what?

Orthostatic reflex

This is the rotation of the eye around a fixation axis

optokinetic nystagmus (OKN) (optokinetic eye movements)

When a stationary observer views unidirectional movement of large object, smooth pursuits alternate with saccades in the opposite direction

cyclopean eye

This is a term used to describe the single representation of the word through sensory fusion

- space perception

- visual localization/direction

What are the two sensory aspects of sensory fusion?

Object space

This is of the real world location of objects that is used in space perception

visual space

This is our perceived vision of object space

visual space

This need to be accurate in space perception to be able to judge and navigate surroundings

Egocentric

Type of visual localization where the object is in 3 dimensional space relative to the head

Stereopsis

Egocentric visual localization includes distance judgements aided by what?

Oculocentric

Type of visual localization in which the directional value is based on the retinal point or the location of an object within the visual field

visually straight ahead

In oculocentric localization objects seen by the fovea are perceived as what?

False (egocentric)

True or False: All judgements of visual direction are ultimately oculocentric

eye is always moving

Why do we need egocentric visual localization?

principle visual direction

The is a specific type of oculocentric direction that arrises from the fovea

corresponding retinal points

pairs of points, one in each eye, that when stimulated simultaneously give rise to a common visual direction

single

When objects are equidistant from the eye they appear what?

zero

corresponding retinal points are said to have how much retinal disparity?

primary visual direction

All oculocentric directions other than the principle visual direction are relative to what?

fovea

All corresponding retinal points have approximately the same relative location to what?

Vieth-Muller circle

the location of objects whose images fall on geometrically corresponding points in the two retinas that make a theoretical circle around the cyclopean eye

Horopter

The location of objects whose images lie on corresponding points.

flattens

The horopter does what as it reaches the periphery

center of range of single binocular vision

This is the region of highest relative stereopsis

Panum's fusional area

Region of space, in front of and behind the horopter, within which binocular single vision is possible

slack in the system

What allows us to see single within Panum's fusional area?

periphery

Panum's Fusional Area is wider within what area of vision?

diplopia

Because panum's fusional area expands toward the periphery, we don't see significant ___________ in real life

physiologic diplopia (normal diplopia) (expected diplopia)

Double vision that occurs outside of panum's fusional area is known as what?

retinal disparity

Binocular cue in which each eye has a slightly different view of the same object due to placement in the head

stereopsis

A small amount of retinal disparity allows for what?

- binasal

- bitemporal

List the two types of non-corresponding points

retinal disparity

Non-corresponding points drive what?

crossed disparity

a type of binocular disparity produced by an object that is closer than the horopter

bitemporal

Crossed disparity is caused by what type of non-corresponding points?

uncrossed disparity

A type of binocular disparity produced by an object that is farther away than the horopter

binasal

Unrossed disparity is caused by what type of non-corresponding points?

convergence

crossed disparity stimulates what?

divergence

uncrossed disparity stimulates what?

stereopsis

The binocular vision perception of three dimensional space based on retinal disparity

stereopsis

This is the reason for binocularity

monocular cues

Depth perception is still possible without stereopsis by using what?

Binocular Test

These types of tests the limits of binocularity to be tested for a patient

single, clear, comfortable, efficient binocular vision (SCCEBV)

The goal of binocular assessment is to test the ability of the patient to maintain what?

Binocular disfunction is a large cause of near point symptoms

Why do we perform a binocular assessment?

- weak

- absent

What are the two categories of binocular dysfunction?

weak binocular disfunction

Which binocular disfunction does a patient most likely have if their binocular skills are reduced from normal values, their binocular skills cannot keep up with the visual demands of the patient's activities of daily life, or their binocular skills are inadequate to compensate for postural abnormalities

absent binocular disfunction

Which binocular disfunction does a patient most likely have if the patient is only using one eye?

- accommodative disorders

- vergence disorders

Weak binocular dysfunction can further be categorized into what types of disorders?

- accommodative insufficiency

- accommodative excess

- ill-sustained accommodation

What are three accommodative disorders that a patient with weak binocularity may have?

- con/divergence insufficiency

- con/divergence excess

- vertical deviation

- fusional vergence disfunction

What are four vergence disorders that a patient with weak binocularity may have?

- strabismus

- amblyopia

Absent binocular disfunctions are typically due to what two things?

- blur

- fatigue

- motion sickness

- asthenopia

- headaches

- diplopia

- words moving on a page

- skipping words/letter/lines

List at least 3 common patient symptoms of binocular disfunction

- disparity of the retina

- drives motor fusion (divergence/convergence)

- Depth (sensory fusion/stereopsis)

What are the 3 D's of "3D"?

accommodative assessments

Binocular assessments parallel what other type of assessment?