Binocular Vision Flashcards
ESSENTIALS FOR BINOCULAR VISION:
- Healthy functioning maculas
- Efficiently working muscular mechanism (motor fusion)
- Efficiently working neural mechanism (sensory fusion)
proper coordination of eyes and brain
NEUROPLASTICITY
PREREQUISITES FOR SINGLE BINOCULAR VISION:
- Frontally placed eyes, overlapping retinal fields
Straight eyes, without deviation - Partial decussation of the optic nerve fibers
- Foveal region stimulated
- Corresponding or identical retinal points
- Size of retinal images Must be equal or nearly equal in size
- Efficient function of extra ocular muscles and nerves
equal size of retinal images
ISEIKONIA
unequal size of retinal images
ANISEIKONIA
equal best corrected visual acuity
ISO-OXYOPIA
unequal best corrected visual acuity
ANISO-OXYOPIA
significant/ high difference of refractive error
ANISOMETROPIA
eye has different refractive status
ANTIMETROPIA
extent of BINOCULAR VISUAL FIELD
180 degrees
extent of COMMON BINOCULAR VISUAL FIELD
120 degrees
extent of MONOCULAR VISUAL FIELD
150 degrees
extent of TEMPORAL CRESCENT
30 degrees
Advantages of Binocular Vision
- Single vision - first and foremost advantage
- Optical defects in one eye are made less obvious by the normal image of the other eye
- Enlarged field of vision
- Power to discriminate details and contours of an object is better with two eyes than with one eye
alone - Loss of one eye will not seriously handicap the individual
- Stereopsis or depth perception
- Compensation of blindspot and other differences
development of binocular vision at birth
- Eyes are not associated with each other; act as two different organs
- VA: not greater than 5/200
- normally hyperopic - because ciliary muscles are not yet fully developed and smaller eyeball
development of binocular vision in newborn
first sign of development of fixation appears when the eyes follow light
development of binocular vision at 2 months
eyes follow large objects
development of binocular vision at 3 months
- Foveas fully formed
- They hold objects
development of binocular vision at 3-4 months
Eyes are expected to be straight
development of binocular vision at 6 months
fixates at an object for 1-2 minutes
development of binocular vision at 1 yr old
VA of 20/70
development of binocular vision 1-1 ½ yr old
fusional mechanism becomes fully developed
development of binocular vision at 3 yrs old
- VA: 20/20
- Accommodation develops with sharpening of visual acuity
development of binocular vision at 7-12 yrs old
Age of emmetropization
A reading matter is positioned at 40 cm/16 inches in front of the patient’s eye; a pen is positioned 2-3 inches over the printed page, so that some of the letters are hidden from the left and other from the right eye. If the patient reads the next text continuously without hesitation, BV is present
BAR READING TEST
- Sufficient amount of prism (usually 6 prism BU or BD) is placed before one eye to induce doubling
- if patient notices diplopia, BV is present
Prism test
Light passing through a prism is bent towards the?
BASE
EYE looking through a prism is displaced on the?
APEX
OBJECT viewed through a prism is displaced on the
APEX
A rolled paper with 2 or fewer diameters is placed before one eye, and is directed at a distant fixation object. The observer’s hand is held up, palm facing the observer at a distance object viewed through the tube
If the patient notice an apparent hole in the hand, BV is present
HOLE IN THE HAND
binocular-like instrument consisting of prism: it makes use of a SEPTUM to separate the image seen by the right and left eye
STEREOSCOPE
- Pressure on temporal side of the eyeball is applied
- If the patient reports doubling of objects in the visual field, BV is present
PRESSING THE EYEBALL
- Position which the eyes assume when with the head erect, point straight ahead on the horizon is fixed upon.
- Ortho position
PRIMARY POSITION
Position in which the eyes assume when the lateral or vertical movements are involved Dextro, levo,supra infra
SECONDARY POSITION
- position in which the eyes assume when it moves in a direction which is a combination of both lateral and vertical movements
- dextrosupra, dextroinfra, levosupra, levoinfra
TERTIARY POSITION
origin of inferior oblique muscle
Inferior Nasal orbital rim
Strongest, heaviest, broadest EOM
MEDIAL RECTUS
EOM that is angled 23 degrees nasally
SUPERIOR RECTUS & INFERIOR RECTUS
longest EOM, about 60mm in length
SUPERIOR OBLIQUE
points of connections of all
recti muscles
Spiral of Tillaux-
Cross diagram that shows which muscle
move when the eye moves to a given
direction
BENZENE RING
AXIS
24 mm
Horizontal line from vertex of the cornea to posterior pole of the eye
Torsional movement
Optic axis/ Y-axis/antero-postero/sagittal axis
AXIS
22 mm
Line passing through the center of rotation of the eyeball and at right angle to
optic axis
Vertical movement
Transverse axis/X-axis
AXIS
22mm
Superior-inferior line passing through center of rotation
Horizontal movement
Vertical axis/ z-axis/supero-infero axis
Lie the optic axis and transverse axis
Divides eyeball to upper and lower portion
Horizontal Plane
Lie the optic axis and vertical axis
Divides eyeball to right and left hemispheres
Median Plane
Lie the transverse axis and vertical axis
Divides eyeball to anterior and posterior halves
Equatorial Plane
Image of the real pupil found at the cornea.
ENTRANCE PUPIL
Point towards which the observer directs his gaze.
OBJECT OF REGARD
Point located 13.5 mm behind the cornea.
◦ All oblique axes pass and it is where the movement of eyes
take place.
CENTER OF ROTATION
Line drawn from the object of regard to the center of
rotation.
LINE OF SIGHT
Line drawn from the object of regard to the fovea passing through
the nodal point.
VISUAL AXIS
Line from the center of entrance pupil and passes through the
center of curvature of the cornea.
◦ Line perpendicular to the cornea and passing through the center
of the entrance pupil of the eye.
PUPILLARY AXIS
An imaginary straight line passing through the midpoint of the
cornea (anterior pole) and the midpoint of the retina (posterior
pole).
OPTIC AXIS
Line connecting the centers of rotation of both eyes.
BASELINE
Plane which includes both the object of regard and baseline.
PLANE OF REGARD
Line in the primary position of the plane of regard which
bisects the baseline
PRIMARY SAGITTAL LINE
Plane tangent to the chin and the two super-ciliary ridges.
FACE PLANE
Conscious and purposeful fixation at an object of regard
VOLUNTARY
Involuntary fixation such as may occur in response to
peripheral retinal stimulation
REFLEX
A rapid change of fixation from one point in the visual field to
another
SACCADIC/JUMP FIXATION
Continued fixation of a moving object, implying a dynamic
movement of the eye so as to keep the image of the object
continuously on the fovea
PURSUIT
Series of rapid fixations associated with an attempt to survey
quickly the details of a view subtending a relatively large area
of the visual field
SCANNING
Continuous and fixed fixation of a non-moving object for a
given period of time
STEADY
Retinal elements of the two eyes that
share a common subjective visual
direction are called?
CORRESPONDING
RETINAL POINTS.
Holds that if the two images of an object fall on
upon identical points in the two retinas, the object
is seen as one,
but if the two images fall upon unidentical or
disparate points, the object is seen as two.
DOCTRINE OF
CORRESPONDING POINTS
A theoretical circle passing through the fixation point
and nodal points (entrance pupil) of the two eyes;
any point from such circle stimulates corresponding
retinal elements.
HOROPTER
A zone infront or behind the horopter in which an
object may lie and still be seen as a single image
despite stimulating non-corresponding elements.
PANUM’S FUSIONAL SPACE
Process by which a single cortical image is
perceived as a result of two separate
ocular ones
Blending of sight
FUSION
States that fusion operates upon a
psychological and cerebral level
WORTH’S THEORY
“Theory of Replacement”/ “Theory of Retinal
Rivalry”
Based upon alternate shifting mosaic patterns
from each ocular image, in which portions of
ocular image of one eye combines with
portions from the other, in varying pattern to
form the final unified or single perceptual
image
VERHOEFF’S THEORY
Maintains that single image is merely a
projection of two identical images to
the same perceptual position and that
two ocular images are perceived as one
because of their community location
WALL’S THEORY
REQUIREMENTS FOR FUSION
Equal or nearly equal visual acuity between two
eyes
Monocular fixation of each eye
Normal sensorial relationship or normal retinal
correspondence
Normal ocular motility
Representation of the crossed and uncrossed
optic nerve fibers in the occipital cortex
COMPENSATORY ACTIONS May be due to problem with oblique muscles
HEAD TILLTING
COMPENSATORY ACTIONS
FACE TURNING
◦ Due to lateral problems (esotropia/exotropia)
FACE TURNING
COMPENSATORY ACTIONS
Due to vertical problems
(hypertropia/hypotropia)
CHIN DEPRESSION/ ELEVATION
Occurs when the amplitude of accommodation
(AA) is lower than expected for the patient’s age
and is not due to sclerosis of the crystalline lens.
usually demonstrates poor accommodative
sustaining ability.
ACCOMMODATIVE INSUFFICIENCY
is a condition in which the AA is
normal, but fatigue occurs with
repeated accommodative stimulation
Accommodation is sufficient but tires
easily
ILL-SUSTAINED ACCOMMODATION /
ACCOMMODATIVE FATIGUE
occurs when the accommodative system is slow
in making change, or when there is considerable
lag between the stimulus to accommodation and
the accommodative response
Difficulty in changing the accommodative state
from one fixation distance to another.
Patients experience difficulty in changing focus
quickly
ACCOMMODATIVE INFACILITY /
ACCOMMODATIVE INERTIA
is a rare condition in which the
accommodative system fails to respond
to any stimulus
Total inability to accommodate due to
ciliary paralysis
ACCOMMODATIVE PARALYSIS
Condition in which the ciliary muscle is
contracted and cannot be relaxed;
accommodation is continously exerted
may be associated with fatigue
It is sometimes part of a triad
(overaccommodation, overconvergence, and
miotic pupils) known as spasm of the near
reflex (SNR).
SPASM OF ACCOMMODATION
Exo at near > Exo at distance
Shows decompensated exophoria for
near vision, but not for distance.
Convergence weakness
Exo at distance > Exo at near
In its typical form, this is an intermittent
divergent squint for distance vision with
compensated exophoria for near vision.
Sometimes it is defined as an exo-
deviation of 15^ greater for distance vision
than for near.
Divergence excess
Exo at distance = Exo at near
Type of exophoria whose degree does
not differ significantly with the fixation
distance
Basic (mixed) exophoria
Eso at distance > Eso at near
Shows decompensated esophoria for
distance vision. In near vision, the
heterophoria will be compensated.
Divergence
insufficiency/weakness
Eso at near > Eso at distance
Type of esophoria with low degree for
distance vision but on converging for near
vision, the convergence impulses seem to
be unusually high. This results in a high
degree of esophoria for near vision.
Convergence excess
Eso at distance = Eso at near
The patient with basic esophoria has high
tonic esophoria at distance, a similar
degree of esophoria at near
Basic (mixed) esophoria
often have normal phorias and AC/A ratios but reduced
fusional vergence amplitudes.
Their zone of clear single binocular vision
(CSBV) is small.
FUSIONAL VERGENCE
DYSFUNCTION
Position assumed by the visual axes when fusion
is suspended.
RELATIVE POSITION OF REST
assumed by the eyes in death before the onset of
rigor mortis, and in deep anesthesia
ABSOLUTE POSITION OF REST
the deviation is, within physiologic limits and for a given
fixation distance, the same in all directions of gaze
COMITANT/CONCOMITANT
one or more extraocular muscles show signs of
underaction or paralysis.
The deviation therefore varies in different directions of
gaze but is larger when the eyes are turned in the
direction of action of the underacting or paralytic
muscle.
INCOMITANT/NONCOMITANT
CLASSIFICATIONS OF HETEROTROPIA that occurs only at certain fixation distance
PERIODIC
CLASSIFICATIONS OF HETEROTROPIA that occurs within the first 6 months of life
INFANTILE
CLASSIFICATIONS OF HETEROTROPIA when deviation of the eye occurs after 6 months
ACQUIRED
Reflex eye movements that stabilize images on
the retina during head movements by
producing an eye movement in the direction
opposite to head movements, reserving the
image on the center of the visual field.
Vestibulo-ocular reflex
The patients’ head is turned fairly and briskly to right and left to
elicit horizontal eye movement or the chin is tilted up and down to
elicit vertical eye movement
Doll’s head movement
This test is based on the observation of the conjugate deviation of
the infants’ eyes in response to head movement induced by
rotation
Swinging baby test
Is the tendency of the eye to deviate inward when
fusion is interrupted
ESOPHORIA
Is the tendency of the eye to deviate outward when
fusion is interrupted
EXOPHORIA
the influence of atmospheric conditions (dust,wind,
vapor) in so far as visibility is concerned, is known
to us all.
In extreme clearness of mountain air, we judge
objects to be much closer and smaller than they
really are. On the other hand, because of the
indistinctness of the outline of objects in foggy
weather, we hold them to be situated at a great
distance and therefore and they appear
correspondingly large.
Aerial Perspective
Parallel lines extending before us appear to
converge. This aids us very largely in our perception
of depth and constantly employed by artist to lend
proper perspective to their work. Object located at
more converging points seem to be farther, objects
located at less converging points/diverging appear
to be nearer.
Mathematical Perspective
the apparent displacement of
an object, seen from two different points in space,
or when seen by the two eyes alternately.
Motion parallax
MONOCULAR CUES OF DEPTH
PERCEPTION wherein The speed of the image can also determine the distance of the object
Velocity
sum of the angles formed between
the visual axes and the line connecting the object to
the part of the retina outside the fovea
Parallactic angle
Superimposition or simultaneous (first
degree fusion) of two ocular images (e.g.,
a bird in the cage) requires stimulation of
retinal areas having common visual
directions.
Superimposition/Simultaneous
Perception
true fusion without stereopsis
It is defined as sensory fusion in which
the resultant percept is two-dimensional,
that is, occupying a single plane as may
induced by viewing a stereogram in which
the separation of all homologous points is
identical.
Flat Fusion
Highest form of fusion
Ability to judge distant objects
the binocular visual perception of three-
dimensional space based on retinal disparity.
Stereopsis/Depth Perception
Diplopia occurring in normal binocular vision for non-fixated
objects whose images stimulate disparate points on the retina
outside of the Panum’s area.
PHYSIOLOGICAL DIPLOPIA
◦ Any diplopia due to an eye disease(e.g. Proptosis),
◦ an anomaly of binocular vision (e.g. Strabismus),
◦ a variation in the refractive index of the media of the eye
(e.g. Cataract)
◦ a subluxation of the crystalline lens
◦ or to a general disease (e.g. Multiple sclerosis, myasthenia
gravis).
PATHOLOGICAL DIPLOPIA
movement of one eye only
DUCTION-
synchronous and symmetric movement of
both eyes in the same direction
VERSION-
synchronous and symmetric movement
of both eyes in the opposite direction
VERGENCE-
right eye turns up
and left eye turns down
POSITIVE VERTICAL DIVERGENCE-
right eye turns
down and left eye turns up
NEGATIVE VERTICAL DIVERGENCE-
vertical
meridians of both eyes rotate inward
INCYCLOVERGENCE/CONCLINATION-
vertical
meridians of both eyes rotate inward
EXCYCLOVERGENCE/DECLINATION-
Ways of Dissociating the eyes
- by covering one eye
- by presenting dissimilar targets
- by using colored filters
- by using prism
refers to esotropia which begins in the developmentally and neurologically normal child during the first 6mos of life. probable age of onset is at 2-4 months
Infantile esotropia
the
incoordianted
dissociations of infancy
before BV is developed
Spurious strabismus
strabismus when both eyes down
Catatropic
strabismus when both eyes up
anatropic
strabismus when both eyes turn up and in
Braids
- associated with the activation of Acc.
- attributed partly to either uncorrected
hyperopia and/or high Accommodative
Convergence/Accommodation (AC/A)
ratio.
Accommodative Esotropia
management of accommodative esotropia
1.Correction of hyperopia and/or prescribe
near add
2.Tx of amblyopia if present
3.Vision Therapy
management of infantile esotropia
- Correction of EOR
- Tx of amblyopia if present.
⚫Occlusion therapy on the preferred eye.
(Direct occlusion)
⚫2hrs daily. Should be monitored every 4-
6weeks. - Surgical ocular alignment
- not associated w/ accommodative effort
- correction of hyperopia and/or
prescribing near add has minimal or no
effect
Non-Accommodative Esotropia
- caused by a mechanical restriction or
tightness or a physical obstruction of the
EOM - can either be congenital or acquired
Mechanical Eso/Exo
management for Mechanical Eso/Exo
- May need no specific therapy if there s
either minimal or no strabismus in the
primary position - Prisms for slight head turns
- Surgery for large head turns
- px sometimes manifests diplopia,
suppresion, or ARC - w/ Tx, may either progress, stay the
same, or in some cases, improve - rarely deteriorates to constant exotropia
Intermittent Exotropia
management of intermittent exotropia
- Case to case basis in therapy
- Correction of EOR. Full amt. of myopia,
anisometropia and astigmatism. Hyperopia
may be undercorrected for younger
patients. - Prism therapy to facilitate fusion
- Vision Therapy
- Surgery
- results from a primary sensory deficit or as a
result of surgical intervention.
Secondary Eso/Exo
- results from visual deprivation or trauma in one
eye. - uncorrected anisometropia, unilateral cataract,
corneal opacity, etc. - occurs more frequently under 5 years of age
Sensory Eso/Exo
- results from visual deprivation or trauma in one
eye. - uncorrected anisometropia, unilateral cataract,
corneal opacity, etc. - occurs more frequently under 5 years of age
Sensory Eso/Exo
management of of sensory eso/exo
- Cataract surgery w/n the first 2 months of
life - optical correction w/ CL
- IOL
- Occlusion therapy
- Prisms
- Vision Therapy
- occurs after surgical overcorrection
- may result in amblyopia in children and
diplopia in adults
Consecutive Eso/Exo
- angle of deviation is less than 10PD
- constant and usually unilateral
- frequently results from the Tx of a larger scale
deviation.
Microesotropia & Microexotropia
This occurs when placing a neutral density
filter over one eye. When you close the
eye with the filter the object looks brighter.
The visual system does not add the
brightness from the 2 eyes.
Fechner’s Paradox
Fibers in that interconnect the two
hemispheres.
connects the left side of the brain to the right side, each side being known as a hemisphere
Corpus Collosum
Lesion at Corpus Collosum
Loss of stereopsis along the midline
Lesion at Corpus Collosum
Loss of stereopsis along the midline
Both fovea have a common visual
direction and the retinal elements nasal to
the fovea in one eye corresponds to the
retinal elements in the other eye.
Normal Retinal Correspondence
Retinal correspondence when
the fovea of one eye has a common visual
direction with an extrafoveal area in the
other eye.
Abnormal Retinal Correspondence
(ARC)
In which the angle of anomaly is equal to the
objective angle of deviation. This
indicates that the ARC fully corresponds to the
strabismus.
Harmonious ARC
In which the angle of anomaly is less than
the objective angle of deviation
Unharmonious ARC
When the angle of anomaly is greater than
the objective angle of deviation.
Paradoxical ARC
Unification of Visual excitations from
corresponding retinal images into a single
visual percept = a single visual image.
An object localized in one and the same visual
direction by stimulation of the two retinas can
only appear as one.
SENSORY FUSION
• The precise co-ordination of the two eyes for
all direction of gazes.
• refers to the vergence movements made by
the eyes in response to retinal disparity and
having the result of obtaining or maintaining
images on corresponding retinal points.
Motor Fusion
• The precise co-ordination of the two eyes for
all direction of gazes.
• refers to the vergence movements made by
the eyes in response to retinal disparity and
having the result of obtaining or maintaining
images on corresponding retinal points.
Motor Fusion
(1950) described the motor fusion as fusion
compulsion.
Ogle
To screen for the presence of third
degree of fusion.
RANDOM DOT E
the basic instrument
used for measuring or
training binocular vision,
for stimulating vision in
an amblyopic eye and
for increasing fusion of
the eyes.
major amblyoscope
One maintained that humans are born without
binocularity or spatial orientation and that
binocularity and spatial orientation are learned
functions acquired by trial and error through
experience and assisted by all the other senses,
especially the kinesthetic sense.
Empiricism or Ontogenic development.
Binocular vision and spatial orientation are not
learned functions but are given to humans with
the anatomicophysiologic organization of his
visual system, which is innate.
Nativism or Phylogenic development.
Unilateral or less commonly, bilateral
reduction of best corrected visual acuity that
can not be attributed directly to the effect of
any structural abnormality of the eye or the
posterior visual pathway. Defect of central
vision.
Ambylopia
- The most common form of amblyopia
thought to result from
competitive or inhibitory interaction between
neurons carrying the nonfusible inputs from
the two eyes.
◼ Which leads to domination of cortical vision
centers by the fixating eye and chronically
reduced responsiveness to the nonfixating eye
input.
Strabismic Amblyopia
◼ Second in frequency
◼ It develops when unequal refractive error in the two
eyes causes the image on the one retina to be
chronically defocused.
◼ This condition is thought to result:
- Partly from the direct effect of image blur in the
development of visual acuity.
- Partly from intraocular competition or inhibition
Anisometropic Amblyopia
hyperopic or astigmatic anisometropia (1 - 2D)
mild amblyopia
Mild myopia anisometropia (less than -3D)
usually doesn’t cause amblyopia
unilateral high myopia (-6D)
severe
amblyopia visual loss.
result from large,
approximately equal, uncorrected refractive
error in both eyes of a young child.
isometropic amblyopia
Hyperopia exceeding 5D & myopia excess of
10 D has a risk of?
bilateral amblyopia
Uncorrected bilateral astigmatism in early
childhood may result in loss of resolving
ability limited to chronically blurred
meridians.
Meridional amblyopia:
◼ It is usually caused by congenital or early
acquired media opacity.
◼ This form of amblyopia is the least common
but most damaging and difficult to treat.
◼ In bilateral cases acuity can be 20/200 or
worse.
Stimulus Deprivation Amblyopia
children younger than 6 years with
congenital cataract that occupy the central 3
mm. or more of the lens,
capable of causing severe amblyopia.
a form of amblyopia deprivation
caused by excessive therapeutic patching.
Occlusion amblyopia
allow
the examiner to test the crowding phenomenon with
isolated optotype. Bar surrounding the optotype
mimic the full optotype to the amblyopic child.
Crowding bar, or contour interaction bars,
allows the examiner to test the crowding phenomenon with
isolated optotype. Bar surrounding the optotype
mimic the full optotype to the amblyopic child.
Crowding bar, or contour interaction bars,
Treatment of amblyopia involves the following
steps:
◼ Eliminating (if possible) any obstacle to vision
such as a cataract
◼ Correcting refractive error
◼ Forcing use of the poorer eye by limiting use
of the better eye.
Designed primarily for screening pre-school children
(age 2.5 to 5 yrs)
for defects of
binocular vision.
TNO TEST
other terms for strabismus
- squint,
- manifest ocular deviation,
- tropia, ophtahlmotropia
- heterotropia, cross eyes,
wall eyes.
Classification of Strabismus
- By the nature of the deviation (comitant/incomitant)
- By behavior (fixed/variable)
- By appearance (manifest/latent)
- By time/frequency/periodicity (Constant/intermittent/periodic)
- By eye (monocular/bilateral/alternating)
- By direction (eso,exo,hyper,hypo)
(1977) presented sinusoidal
gratings at various orientations and spatial
frequencies to normal and strabismic
subjects.
Schor
occurs at a later age than infantile esotropia usually, normal binocular vision has existed prior to the onset of the condition
acquired esotropia
a convergent strabismus which develops suddenly without apparent etiology in school-aged or adult patients with previously normal binocular vision
acute esotropia
caused by mechanical restriction or tightness of an EOM or a physical obstruction of the EOM
MECHANICAL ESOTROPIA
for the patient to experience comfort, the fusional reserve should be twice or more than twice the fusional demand
Sheard’s criterion
often is used to describe amblyopia, which is potentionally reversible by occlusion therapy
functional amblyopia
often is used to describe amblyopia, which is potentionally reversible by occlusion therapy
functional amblyopia
- amblyopia in which ocular pathology is not obvious
- refers to irreversible amblyopia
Organic amblyopia
period of highest risk of deprivation amblyopia
few months to 7 or 8 yrs
amblyopia which is due to causes such as hysteria or malingering. common in children and adults in stressful situations
Psychogenic amblyopia
amblyopia which is due to causes such as hysteria or malingering. common in children and adults in stressful situations
Psychogenic amblyopia
- a suppression that occurs wherein only when the eyes are misaligned
- example is intermittent exotropia
Facultative suppression
a suppression that is present at all times, irrespective of whether the eyes are deviated or straight
Obligatory suppression
