Download Strabismus

Strabismus
Dr HAN Wei
The 1st Affiliated Hospital, Medical College,
Zhejiang University
Basic knowledge of ocular motility
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Extraocular muscles
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Not playing role in vision procedure directly,
but critically important for eyeball motility and
binocular vision function.
Anatomy of extraocular muscles
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Six extra-ocular muscles
for the human eye.
Namely:
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Medial rectus m.
Lateral rectus m.
Superior rectus m.
Inferior rectus m.
Superior oblique m.
Inferior oblique m.
Insertion positions of four rectus m.
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MR: Medial rectus m.
LR: Lateral rectus m.
SR: Superior rectus m.
IR: Inferior rectus m.
Nerve innervation for extraocular m.
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III cranial n.
 Medial rectus m.
 Superior rectus m.
 Inferior rectus m.
 Inferior oblique m.
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IV (Trochlea) cranial n.
 Superior oblique m.
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VI (Abduction) cranial n.
 Lateral rectus m.
Basic motility function of the eye ball
Elevation and depression (A, B)
Adduction and abduction (C, D)
Intorsion and extorsion (E, F)
Motility functions of right eye’s extraocular muscle
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Inferior oblique m.
 Extorsion
 Elevation
 Adduction
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Superior rectus m.
 Elevation
 Intorsion
 Adduction
Lateral rectus m.
 Abduction
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Superior oblique m.
 Intorsion
 Depression
 Abduction
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Medial rectus m.
 Adduction
Inferior rectus m.
 Depression
 Adduction
 Extorsion
Terminology of extra-ocular muscle regarding their
physiological functions
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Antagonist m.:
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Yoke m. :
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the muscle that counteracts the agonist (or the prime mover);
lengthening when the agonist muscle contracts.
e.g., medial rectus and lateral rectus m..
The contra-laterally paired extra-ocular muscles of two fellow eyes that
work synergistically to direct the gaze in a given direction.
Example: in directing the gaze to the right, the right lateral rectus and
left medial rectus operate together as yoke muscles.
Synergist m.:
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The muscles moving one single eye ball in the same direction as the
prime moving muscle.
e.g., inferior oblique m. is the synergist of superior rectus m. when the
eye turns upward.
Nervous innervation laws
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Sherrington law:
 A muscle
will relax when its antagonist muscle
(e.g., lateral and medial m.) is activated.
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Hering law:
 The
yoke m. are innervated equally by nervous
system in eye movement.
Eye position for examination
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Primary position:
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Secondary position:
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With condition in which head being put vertically and
straightforward and two eyes looking straightforward.
The two eyes being in adduction or abduction or elevation or
depression position.
Tertiary position:
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Two eyes gazing in oblique directions (up or downward).
Right Superior rectus m.
Left Superior rectus m.
Right Superior rectus m.
Left inferior oblique m.
Left superior rectus m.
Left superior rectus m.
Right inferior oblique m.
Right superior rectus m.
Left medial rectus m.
Right lateral rectus m.
Right medial rectus m.
Left lateral rectus m.
Right inferior rectus m.
Left superior oblique m.
Left inferior rectus m.
Left inferior rectus m.
Right inferior rectus m.
Right superior oblique m.
Right Inferior rectus m.
Left Inferior rectus m.
Definitions
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Strabismus:
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A condition in which the eyes are not properly aligned with
each other, i.e., manifest deviation of the eyes exist.
Heterophoria:
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A condition in which the visual axes of two eyes fail to
remain parallel after elimination of visual fusional stimuli.
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e.g, covering one eye
Classification
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Based on concomitancy
 Concomitant: Angle of squint is the same in all directions
of gaze.
 Exotropia
 Esotropia
 Inconcomitant: Angle differs in different directions of gaze.
 Special types: e.g., Duane syndrome
Based on etiology
 Functional
 Paralytic (secondary to traumatic or pathological lesions)
Based on constancy
 Constant
 Single eye deviation
 Alternative deviation
 Intermittent
Examination and diagnosis
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Disease and familial history
Onset age
Visual acuity
Refraction
Strabismus type
Compensative head position
Test for strabismus*
Epicanthal fold – should be ruled out in child patients
Simulated esotropia
Strabismus test (1)
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Cover test and uncover test
Alternative cover test
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A
B
Unilateral gaze (A) or alternative gaze (B)
Strabismus test (2)
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Corneal reflex test
Simple, easy method
 Broadly applied in clinic
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Strabismus test (2)
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Other methods
Prism and cover test
 Perimeter arc test
 Maddox rod test
 Synoptophore test
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Concomitant strabismus
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Accommodative
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Complete accommodative
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Partially accommodative
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Non-accommodative
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First deviation angle = Secondary deviation angle
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First deviation angle: When the normal eye
gazing target, the strabismus angle of the
deviated eye.
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Second deviation angle: When deviated eye
gazing target, the strabismus angle of the
normal eye.
Concomitant esotropia
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Most commonly seen type, closely associated
with accommodation function.
First angle = Second angle
Usually no diplopia
Normal ocular motility
Intermittent in incipient stage and turn to be
constant gradually.
Treatment
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Spectacle correction for ametropia
Treat amblyopia
Eye position training
Surgery
An example of concomitant esotropia
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After operation, the two eyes’ position is corrected to be
normal. (Lower figure)
An example of partially accommodative concomitant esotropia
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With spectacle, squint was partially corrected, but still
existed. (lower figure)
Concomitant exotropia
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Associated with:
 Central nervous biocular balancing function,
 Imbalance of accommodation and convergence,
 Anisometropia
 Visual impairment in one eye
Intermittent early stage to constant stage.
Treatment:
 Ametropia correction
 Prism spectacle
 Surgery
An example of concomitant exotropia treated by surgery
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Deviation was correctly after surgery. (Figure left)
An example of concomitant exotropia due to visual
impairment in left eye
Nonconcomitant strabismus
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Usually paralytic secondary to:
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Embryo development anomalies
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Trauma
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Inflammation
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Hypertension and hemorraghe & ischemia
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Tumor
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Metabolism disorder like diabetes, thyroidism, etc
Symptoms
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Diplopia
Compensation head position
Deviation of affected eye
First angle ＜ second angle
Compromise of ocular motility
Hess screen test
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Shift of the square denotes the muscle being paralytic.
Compensation head position in paralysis of the
right eye’s lateral rectus muscle
An example of paralytic esotropia
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Lateral rectus m. of right eye paralysis. Note the 1st angle (figure right) is less
than second angle (figure left)
An example of paralytic vertical strabismus of
right inferior rectus m.
Treatment
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Primary diseases treatment
Drug
 Vit B1, B12, ATP
 Steroid
 Antibiotics
 Botulinum A injection to relief the muscle spasm
 Prism
Surgery
 Usually 6 months after onset, with deviation being stable.
Differentiation of paralytic and concomittent strabismus
Paralytic
Concomittent
Onset
Suddenly
Gradually
Eye motility
Compromised in affected
m. movement direction
Normal
Deviation angle
2nd angle > 1st angle
Equal
Diplopia
Yes
No
Compensative head
position
Yes
No
Amblyopia
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Definition of amblyopia: otherwise known as lazy
eye, is a disorder of the visual system that is
characterized by poor or indistinct vision in an eye that
is otherwise physically normal.
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It has been estimated to affect 1–5% of the population.
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Etiology: The nerve pathway from one eye to the brain
does not develop during childhood or the abnormal eye
sends a blurred image to the brain.
Category of etiology
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Strabismus
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Anisometropia
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(Double eye onset)
Form deprivation
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(Imbalance of visual input)
Ametropia
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(Most common type, due to crossing eye)
(Refractive media opacity)
Others
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(Pathological lesions)
Symptoms
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Vision acuity loss
Mild:
 Moderate:
 Severe:
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0.6-0.8
0.2-0.5
less than 0.1
Abnormal fixation
Crowding phenomenon
Treatment (1)
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Early treatment.
As early as possible. Critically important!
Treatment effect is poor after 9 years old.
Treatment (2)
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Ametropia correction: spectacle even LASIK, surgery
for congenital cataract.
Occlusion therapy
 Occluding normal eye, allowing amblyopic eye
to develop
Red light therapy
 Stimulating the macular function development
After image therapy
Depression therapy
 Using atropine or over- or under-correction lens
Synoptophore therapy
Drug (L-Dopa)
Nystagmus
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A condition of involuntary rhythmically oscillation of the
globe.
 According to the rhythm, it is divided into two sorts:
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jerky and pendular.
Physiological and pathological
Category:
 Perpetual
 Opticokinetic
 Labyrinthine
 Environmental
Binocular vision
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Normal human’s vision is the matter of the coordination of the two eyes.
The eyes must be capable of aligning themselves in
such a manner: the retinal images of a fixated target
can easily be placed and maintained on the foveae of
the two eyes.
Normal binocular vision is established in about 5-6
years.
Binocular vision
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Condition of the normal binocular vision :
(1) in good focus;
 (2) similar image size (within 5% disparity);
 (3) similar image shape;
 (4) normal eyes’ motility;
 (5) fusion ability and area;
 (6) normal neural pathways.
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Grade of binocular vision
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Simultaneous perception
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Fusion
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Ability to simultaneously
percept the retinal image of
the two eyes
Images formed on the retina of
the two eyes are combined
into a single percept.
Stereopsis
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Highest grade of binocular
vision. Perception of depth
and distance.
Normal binocular vision
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Sensory aspects
 Corresponding retinal points
 Panum fusional areas
 Horopter
 Physiological diplopia
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Motor aspects
 Conjugate movement
 Saccadic movement
 Following movement
 Disconjugate movement
 Convergence
 Divergence
 Motor fusion
Abnormal binocular vision
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Diplopia
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Confusion
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amblyopia
Abnormal retinal correspondence
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misalignment of the two eyes in paralytic strabismus
Suppression
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pathological
strabismus
Eccentric fixation
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amblyopia
Low vision
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Definition of low vision (WHO 1992)
 Best corrected visual acuity <0.3,
 Semi-visual field narrower than 10 degree
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Treatment
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Etiological diseases if viable
Visual aid instruments
 Telescope
 Magnifier
 Electronic apparatus like CCTV, computer display
Low vision aid products
Questions
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State refractive components of the eye’s
optical system.
The category of myopia and the clinical
management?
The classification of the concomittent
strabismus and the clinical management?