Strabismus and the Binocular Single Vision

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Author thanks all of our teachers, fellow ophthalmologists, publishers, sponsors, and all manufacturers for their works those

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Strabismus

• Squint• Misalignment of extra ocular muscle• Misalignment of eye position• Misalignment of eye movement• Disorder in fusion• Disorder visual function Binocular single

vision (BSV)

Position of gaze• Primary position

– Straight ahead• Secondary position

– Straight up, straight down– Right gaze, left gaze

• Tertiary position Four oblique position– Up and right, up and left– Down and right, down and left

• Cardinal position

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Extra ocular muscle (EOM)• Agonist

– Primary muscle moving the eye in a GIVEN direction

• Synergist– Muscle in the same eye– As the agonist– That can act with agonist– Produce a GIVEN movement– E.g : Superior rectus with Inferior oblique elevate the eye

• Antagonist – Muscle in the same eye as the agonist– That can act with in the direction opposite – E.g : Medial rectus and lateral rectus

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Cardinal position and Yoke muscles

RLRLMR

LLRRMR

RSRLIO

LSRRIO

RIRLSO

LIRRSO

Right Gaze Left Gaze

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Basic

• Yoke muscle– Two muscle (one in each eye)– Are Prime mover of their respective eyes– In GIVEN position gaze– E.g : right gaze RLR and LMR simultaneously innervated

and contracted to be “yoked” together

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Basic

• Sherrington’s law for reciprocal innervation– Increased innervation and contraction of GIVEN EOM – Accompanied by reciprocal decrease of innervation and

contraction of its antagonist EOM

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• Hering’s law of motor correspondence– The state equal and simultaneous innervation

flow to Yoke muscle– Concerned with the desired direction of the gaze

Basic

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Monocular eye movements

A- elevation B- depression C- abduction D- adduction E–extortion F- intortion

Muscle Primary Secondary Lateral rectus Abduction None

Medial rectus Adduction None

Superior rectus Elevation Adduction

Intorsion

Inferior rectus Depression Adduction

Extorsion

Superior oblique Intorsion Depression

Abduction

Inferior oblique Extorsion Elevation

Abduction

EOM : Functions

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Eye movement• Versions

– Eyes move in the same direction

• Vergences Disconjugate binocular eye movement– Convergence– Divergence– Incyclovergence– Excyclovergence – Vertical vergence

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Classification of strabismus

A. Pseudostrabismus (false or apparent squint).

B. True strabismus: 1. Latent squint (heterophoria) 2. Manifest squint (heterotropia)

- non-paralytic (concomitant)

- paralytic (non-concomitant)

Variation of deviation

With gaze position or fixating eye• Comitant (Concomitant)

– Deviation doesn’t vary in size with direction of gaze or fixating eye

• Incomitant (Noncomitant)– Deviation varies in size with direction of gaze or fixating

eye– Most paralytic or restrictive– In acquired condition may indicate neurologic or orbital

problems or diseases

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Pseudo-strabismus• In young infants,

strabismus must be differentiated from the more common pseudo-strabismus

• Pseudo-esotropia as a result of a broad bridge of the nose. This is not a real eye crossing

Pseudo-deviations

Pseudo-esotropia Pseudo-exotropia

• Epicanthic folds• Short inter- pupillary distance• Negative angle kappa

• Wide interpupillary distance• Positive angle kappa

In high myopia the, the fovea lies nasal to the optical axis. So, the corneal reflex lies temporal to the center of the cornea Negative angle kappa .

Large negative angle kappa (myopia) leads to pseudo-esotropia.

Large positive angle kappa (hypermetropia) leads to pseudo-exotropia.

(Brief) Classification of squint

• Latent (Heterophoria)– Esophoria– Exophoria– Vertical ‘phoria– Fully compensated– Poorly compensated

(Brief) Classification of squint

• Manifest (Heterotropia)– Esotropia (convergent)– Exotropia (divergent)– Vertical– Unilateral or alternating– Constant or intermittent (in Primary position, or in

certain positions of gaze)– Accommodative

Assessment of squint

• Visual Acuity• Cover Test• Ocular Movements• Convergence• Fusion/Stereopsis?• Measurement of angle (prisms)

Visual aquity

• Recognition acuity : Lea symbols, HOTV, Snellen Chart

• Detection acuity : Stycar Ball test

• Resolution acuity : Lea Paddles

Sensory evaluation

• Simultaneous macular perception

• Worth four dot test

• Stereopsis

Tests for sensory anomaliesWorth four-dot test

a - Prior to use of glassesb - Normal c - Left suppression/amblyopia

Bagolini striated glasses

a - Normal or ARCb- Diplopiac - Suppression

d - Right suppression/amblyopiae - Diplopia

d - Small suppression scotoma

• Qualitative tests for Stereopsis: – Lang’s 2 pencil

test – Synoptophore

• Quantitative tests for Stereopsis: – Random dot test – TNO Test – Lang’s stereo test

Tests for stereopsisTitmus

• Red-green spectacles

TNO random dot test

• ‘Hidden’ shapes seen • Polaroid spectacles• Figures seen in 3-D

Lang

• No spectacles

Frisby

• ‘Hidden’ circle seen

• No spectacles• Shapes seen

Motor evaluation

• Extra ocular muscles• Cover test• Corneal reflex test – Hirschberg

Krimsky

Bruckner• Dissimilar image test – Maddox rod

Evaluation of motility

• Two principle methods of evaluating ocular motility are:

1. Observation of ocular ductions, which are the actual monocular movements of the eye.

2. Observation of binocular ocular alignment, using cover/uncover and alternate cover testing.

Cover test: Exotropia

Cover test: Esotropia

Cover uncover test: Exophoria

Cover uncover test: Esophoria

Cover test detects heterotropia

Uncover test detects heterophoria

Alternate cover test detects total deviation

Prism cover test measures total deviation

Motility testsTests versions and ductionsGrades under/overaction

Left inferior oblique overaction Left lateral rectus underaction

Hirschberg test

Krimsky test

Modified Krimsky test

• Asymmetric positions of the corneal reflex in the pupils of each eye are indicative of strabismus, which may be measured by placing a prism before the fixating eye until the reflection is similarly positioned in both eyes

• Base out prism for esotropia • Base in prism for exotropia• This is the direct reading of the squint

angle.

Bruckner test

• Is performed by using direct ophthalmoscope to obtain a red reflex simultaneously in both eyes.

• If there is strabismus , the deviated eye will have a lighter and brighter reflex than the fixing eye.

• Media opacities, Refractive errors, Strabismus

Dissimilar image testsMaddox wing Maddox rod

• Dissociates eyes for near fixation (1/3 m) • Measures heterophoria

• White spot converted into red streak • Cannot differentiate tropia from phoria

Measurements of ocular misalignment

• Synoptophore - picture test

• Measure - misalignments, sensory and motor fusion and stereopsis

• Predict BV post-surgery • Measure misalignments

9 positions of gaze

Key notes

• Early intermittent neonatal misalignment common between birth and 2-4 months

• BSV well established from 6 months• Sensitive period for development of vision and

binocular reflexes• Suspected squint after 4 months (corrected)

age should be referred for orthoptic assessment

Aniseikonia• Translated from Greek aniseikonia means

"unequal images". • It is a binocular condition, so the image in one

eye is perceived as different in size compared to the image in the other eye.

• Two different types of aniseikonia can be differentiated: static and dynamic aniseikonia

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Aniseikonia• Static aniseikonia or aniseikonia in

short means that in a static situation where the eyes are gazing in a certain direction

• The perceived (peripheral) images are different in size

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Aniseikonia : Static

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Aniseikonia• Dynamic aniseikonia or (optically

induced) anisophoria means that the eyes have to rotate a different amount to gaze (i.e. look with the sharpest vision) at the same point in space

• This is especially difficult for eye rotations in the vertical direction

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Aniseikonia : Dynamic

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Prismatic effect of decentred lens

• Convex lens two prisms cemented together at their BASEs

• Concave lens two prisms cemented together at their APEXs

• Decentred lens Prism effect Base in or Base out

Decrease convergence

Increase convergence

Anisophoria

• Is a condition in which the balance of the vertical muscles of one eye differs from that of the other eye the visual lines do not lie in the same horizontal plane

• Eye muscle imbalance the horizontal visual plane of one eye is different from that of the other

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AmblyopiaType :• Strabismic amblyopia

– Frequently in esotropia patients

• Anisometropic (Refractive) amblyopia– Difference in refraction greater than 2.50 D

• Isoametropic amblyopia– Bilateral refractive error grater than + 5.00 or – 10.00 D

• Deprivation amblyopia– Caused by such as media opacities

Deborah Pavan-Langston, 200849

Management of squint

• Orthoptic assessment• Cycloplegic refraction & fundoscopy• Correct significant refractive error• Allow for refractive adaptation (up to 6/18)• Occlusion treatment for amblyopia (patches,

atropine)• Orthoptic exercises (intermittent deviations)• Surgery

Binocular Single Vision

Leonardo Da Vinci had realized that two images would be needed for stereo viewing, but never created a 3D painting

Early history

• 1838 Wheatstone Stereoscopes– 1848 Brewseter– 1881 Popularized by Oliver Wendell Holmes

• 1853 Earliest Anaglyph photographs

Viewmaster1939-Today Equivalent

20th Century• 1908 Lippmann, Integral Imaging, Lenticular Printing• 1934 Polarizing Glasses (two synchronized projectors)• 1950s Anaglyph and polarizing glasses popular to counter

rise of television• Next 3D picture and 3D motion picture

Journal of Medical Science and Clinical Research Volume1||Issue3||Pages149-154||2013

New Approach In Binocular Single Vision Assessment For Candidate Of Phacoemulsification Micro Surgeons

Gede Pardianto1, Diyah Purworini2

1 Department of Ophthalmology, Komang Makes Hospital Belawan, Medan, North Sumatra, Indonesia

2 Putri Hijau Hospital, Medan, North Sumatra, Indonesia

BSV

• State of simultaneous vision• Coordinated use of both eyes• Blending of sight from the two eyes to form a

single percept

BSV

• Normal– it is bifoveal– there is no manifest deviation.

• Anomalous– images of the fixated object are projected from

the fovea of one eye and an extrafoveal area of the other eye

BSV: Requires

• Clear Visual Axis in both eyes• The ability of the retino-cortical to promote

the fusion of two slightly dissimilar images Sensory fusion

• The precise co-ordination of the two eyes for all direction of gazes to deal with two images Motor fusion

BSV: Advantage

• Single vision.• The most precise kind of depth perception• Enlargement of the field of vision• Compensation for blind spot and other

differences

BSV

3 levels– Simultaneous perception ( 2 images seen)– Fusion (Interpreting 2 images as one)– Stereopsis (3-D appreciation)

Development of BSV

Most neonates show coarse re-fixation1.Conjugate fixation 1st to develop (eyes follow

object together)2.Disjugate fixation (follow approaching object –

convergence)3.Fusional reflex (correct for change in image

position)4.Kinetic reflex (controlled accommodation &

convergence)

Stereo fusion• Objects are “fused” when brain interprets

disparate images in the two eyes as being the same object and perceives the depth of the objects

• When disparity gets too large – Double vision,– or brain ignores input from one eye

Corresponding points

• Pairs of points on each retina share a common visual direction

• A point on the nasal retina of one eye will have a corresponding point on the temporal retina of the other eye

Normal retinal correspondence

• Retinal correspondence is called normal when both the fovea have a common visual direction

• The retinal elements nasal to the fovea in one eye corresponds to the retinal elements temporal to the fovea in the other eye

Abnormal retinal correspondence

• The fovea of one eye has a common visual direction with an extrafoveal area in the other eye

• This results in the eyes seeing binocularly single inspite of a manifest squint

• When the normal eye is closed the extrafoveal element loses any advantage over the fovea of that eye central fixation is over handled by the fovea the anomalous eye moving to primary position this is the basis of the cover test

Retinal rivalry

• When dissimilar contours are presented to corresponding retinal areas fusion becomes impossible retinal rivalry leads to confusion.

• In order to remove this confusion image from one of the eyes is suppressed.

Horopter

A horopter is an infinitely thin plane drawn through all object points that project onto corresponding retinal points.

Panum’s fusional area

• Range of depth’s that can be “fused”

Panum’s fusional area

Binocular Convergence

Monocular Cue

• Non-stereo depth cue• One eye can judge its• Patients with binocular vision defect still

can feel the depth perception

Monocular Cue

• Occlusion near objects block the view of distant objects

• Apparent size if two objects are actually the same size, but one appears smaller, then the small one is farther away than the larger relative size

• Motion parallax and Relative velocity near objects appear move faster than distant objects

• Light and Shading distance and colour• Overlapping contour*

Relative size

Motion parallax

Motion parallax

• Translocation of the head• Cause the images of near objects to move

opposite the head • The images of far objects to move with the

head • Assuming the fixation point is at an

intermediate distance

Light and shade

Over-lapping contours

Monocular cue• Perspective parallel lines converge in the

distance• Aerial perspective• Geometric perspective • Texture becomes finer with distance• Colour change colour becomes more blue

with distance Atmospheric effect• Haze objects become fuzzy in the distance• Accommodation our brain knows how hard

our eyes are working to focus

Aerial perspective

Geometric perspective

Refractive age

Depth perception

Monocular cuesNon stereoscopic binocular cluesStereopsis

Why fovea/periphery differences

• Range of disparities in natural scenes. • Fovea - high depth acuity.• Periphery - provides coarse information about

where to make convergence eye movements.

Mistake in BSV• Motoric

– Squint• Refractive

– Aniseikonia• Eye Sensoric

– Amblyopia• Optical problems

– Visual illusion• Brain Perception

– Experience– Monocular cues– Visual illusion

Visual illusion

Visual illusion

Visual illusion

Visual illusion

Visual illusion

Size illusion

Beuchet chair

Beuchet chair

Ames room

Ames room

Visual illusion: Shadow effect

Visual illusion: Shadow effect

Visual illusion: just 2D

Visual illusion: Moving texture

Visual illusion: Colour

Visual illusion: Grid illusion

Visual illusion: Bleeped-up

Visual illusion: The confuse

Visual illusion: Floor painting

Visual illusion: Single photo

Visual illusion: Single photo

Visual illusion: Bistable

Visual illusion: Bistable

Visual illusion: Bistable

Visual illusion: Mirage

A superior mirage occurs when the air below the line of sight is colder than the air above it.

A inferior mirage occurs when the air below the line of sight is hotter and has lower index bias than the air above it.

Mirage: hot haze

Heat shimmer refers to the inferior mirage experienced when viewing objects through a layer of heated air

Visual illusion: Moonbow

Visual illusion: HaloA sun dog (or sundog), mock sunor phantom sun, scientific name parhelion (plural parhelia), is an atmospheric phenomenon that creates bright spots of light in the sky, often on a luminous ring or halo on either side of the sun.

Sundogs may appear as a colored patch of light to the left or right of the sun, 22° distant and at the same distance above the horizon as the sun, and in ice halos.

They can be seen anywhere in the world during any season, but they are not always obvious or bright.

Sundogs are best seen and are most conspicuous when the sun is low.

Sunset green flash

The optical phenomenon known as the green flash can occur at sunrise or sunset, and it’s most often seen over low, unobstructed horizons such as the ocean.

Sun pillar

A Sun pillar is an atmospheric phenomenon caused when high-altitude ice crystals reflect the rising or setting Sun’s reddened light.

Scintillation or Grid illusion

Visual illusion: Optic1. Thermal Inversion

The Titanic was sailing from Gulf Stream waters into the frigid Labrador Current, where the air column was cooling from the bottom up, creating a thermal inversion: layers of cold air below layers of warmer air.

Extraordinarily high air pressure kept the air free of fog.

Visual illusion: Optic2. Superior Mirage

A thermal inversion refracts light abnormally and can create a superior mirage: Objects appear higher (and therefore nearer) than they actually are, before a false horizon.

The area between the false horizon and the true one may appear as haze.

Visual illusion: Optic3. Iceberg Camouflage

The Californian’s radio operator warned the Titanic of ice. But the moonless night provided little contrast, and a calm sea masked the line between the true and false horizons, camouflaging the iceberg.

A Titanic lookout sounded the alarm when the berg was about a mile away—too late.

Visual illusion: Optic

4. Mistaken Identity• Shortly before the collision,

the Titanic sailed into the Californian’s view—but it appeared too near and small to be the great ocean liner.

• Californian captain Stanley Lord knew the Titanic was the only other ship in the area with a radio, and so concluded this ship did not have one.

Visual illusion: Optic5. Morse Lamp• Lord said he repeatedly

had someone signal the ship by Morse lamp “and she did not take the slightest notice of it.”

• The Titanic, now in trouble, signaled the Californian by Morse lamp, also to no avail.

• The abnormally stratified air was distorting and disrupting the signals.

Visual illusion: Optic

6. Distress Rockets Ignored• The Titanic fired distress

rockets some 600 feet into the air—but they appeared to be much lower relative to the ship.

• Those aboard the Californian, unsure of what they saw, ignored the signals.

• When the Titanic sank, at 2:20 a.m. April 15, they thought the ship might be simply sailing away.

Conflicting Cues: Only binocular• Random Dot Stereograms

Conflicting Cues: Only binocular• Random Dot Stereograms

3D ability: 3D movie

The archetypal 3D glasses, with modern red and cyan color filters, similar to the red/green and red/blue lenses used to view early anaglyph films.

3D ability: 3D movie

Resembling sunglasses, polarized glasses are now the standard for theatrical releases and theme park attractions.

3D ability: 3D movie

A pair of LCD shutter glasses used to view XpanD 3D films. The thick frames conceal the electronics and batteries

3D vision ability

3D vision ability

3D vision ability

3D vision ability

3D vision ability

3D vision ability

3D vision ability

3D vision ability

3D vision ability

3D vision ability

3D vision ability

3D vision ability

3D vision ability

3D vision ability

3D Vision: Game

The hidden tiger

Shape of life: Pareidolia

Loch Ness Monster

Loch Ness Monster

Beyond the lecture

• I have seen with my own eyes!• So now…• What do you think?• Seeing doesn’t mean believing• Think again!