Motor adaptation in paretic and nonparetic strabismus
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Transcript of Motor adaptation in paretic and nonparetic strabismus
KO PI LA KAF LE B . OP TOM ET RY
TH I R D Y EAR
MOTOR ADAPTATION IN PARETIC AND NONPARETIC
STRABISMUS
Moderator : Mr. Gaurishankhar Shrestha
PRESENTATION LAYOUT
Introduction to strabismus and its types
Ways of motor adaptation
Reasons for motor adaptation
Motor adaptation in different conditions of
muscle palsy
Motor adaptation in restrictive disorders
STRABISMUS
Aka SQUINT is deviation of eye
Misalignment of the visual axes of the two eyes
TYPES OF STRABISMUS
Can be COMITANT or INCOMITANT
INCOMITANT COMITANT
Results when there is limitation of ocular movement
Result of abnormality in establishment of normal BSV
Can be paralytic or non paralytic
Always non paralytic
limitation of ocular movement normal extraocular motility
particular abnormal head posture develops ,I.E motor adatation occurs
no head posture ,instead sensory adaptation occurs
Muscle sequelae present in old cases
Absence of muscle sequelae
EXAMPLES
INCOMITANT STRABISMUS COMITANT STRABISMUS A . NEUROGENIC A . PRIMARY STRABISMUS due to palsy of third ,fourth and sixth cranial nerveB . MYOGENIC B . SECONDARY STRABISMUS due to problem affecting muscle itselfC . MECHANICAL C .CONSECUTIVE STRABISMUS due to interference with muscle contraction and relaxation
CONSEQUENCE OF STRABISMUS
WHAT TO DO NOW?
I THINK I NEED TO ADAPT
SENSORY ADAPTATION
MOTOR ADAPTATIO
N
Neither I want to see double
Nor I want to be confused
IN COMITANT STRABISMUS
Sensory adaptation occursAbnormal retinal correspondence
suppression
amblyopia
IN INCOMITANT STRABISMUS
Motor adaptation occurs
WAYS OF MOTOR ADAPTATION
Control of ocular deviation by an alteration of tone of extraocular muscles
Compensatory head posture
Blind spot syndrome
Blind spot mechanism
Control of ocular deviation by an alteration of tone of EOM
Can control only small degree of ocular deviation
active contraction or an active relaxation
compelling fusion reflexes
disappearance of squint(manifest deviation converted to latent one)
BLIND SPOT SYNDROME
In esotropia of 12 – 18 ˚ with good visual acuity in both eye
Normal retinal correspondence and normal fusional vergence present
Eye further moved to esotropic side projecting image seen by deviating eye onto blind spot
BLIND SPOT MECHANISM
Coincidental type of esotropia
Image of fixated object falls on the blind spot
BLIND SPOT SYNDROME BLIND SPOT MECHANISM
Good visual acuity in both eyes Amblyopia of the non dominant eye
Normal retinal correspondence Abnormal retinal correspondence
No suppression other than fovea of the deviated eye
ARC and suppression may coexist
Compensatory head posture
Used by visually mature patients(does not necessarily develops in every patients)
Occurs in paralytic strabismus and alphabet pattern strabismus
Has 3 components
HEAD TILT
FACE TURN
CHIN ELEVATION
OR DEPRESSIO
N
WHAT ACTUALLY IS PARALYSIS?
Malfunctioning or dysfunctioning of nerves
Paralysis = no movement is possible
Paretic = some movement is possible
Palsy = includes both paresis and paralysis (generally used )
CRANIAL NERVES SUPPLYING EOMs
Occulomotor (3rd cranial nerve) : supplies SR,IR,IO and MR
Trochlear nerve (4th cranial nerve) : supplies SO
Abducens nerve(6th cranial nerve) : supplies LR
TO KNOW THIS FIRST WE MUST KNOW ACTIONS OF EXTRAOCULAR MUSCLES
WHAT HAPPENS WHEN THESE NERVES GET PARALYSED?
ACTIONS OF EOM
LATERAL RECTUS AND
MEDIAL RECTUS HAVE ONLY
PRIMARY ACTIONS
MEDIAL RECTUS adducts the eye
LATERAL RECTUS abducts the eye
NOTES
Vertical rectus i.e superior and inferior rectus have their primary function as elevator and depressor while secondary action as intorsion and extorsion
For oblique muscle opposite is true
SIN : all superiors are intorters
RAD : all vertical rectus are adducters
LET’S TRY THEN….
SUPERIOR RECTUSA. ELEVATORB. INTORTERC. ADDUCTOR
INFERIOR RECTUSD. DEPRESSORE. EXTORTERF. ADDUCTOR
SUPERIOR OBLIQUE
A. INTORSIONB. DEPRESSORC. ABDUCTION
INFERIOR OBLIQUE
D. EXTORSIONE. ELEVATOR
F. ABDUCTION
IN CASE OF PALSY,
Actions of muscles interrupted
SO, eye takes its position opposite to its action
For example,in LR palsy,eye is in adducted position
in MR palsy,eye is in abducted position
QUESTIONS
WHAT IS EYE POSITION IN
SUPERIOR RECTUS PALSY?
DEPRESSED
EXTORTED
ABDUCTED
WHAT IS EYE POSITION IN INFERIOR OBLIQUE
PALSY?
INTORTED
DEPRESSED
ADDUCTED
Less to be worried about…
In case of palsy, there is usually some direction of binocular gaze in which the visual axes are approximately parallel in which BSV can be obtained
COMPENSATORY HEAD POSTURE
Normal effect of tilting the head
LE is extorted ,so tilting to the right overcomes this disability,visual axes of both eye parallel
In primary position without head posture,LE hypotropic
In dextroversion ,parallelism of visual axes
Updrift of right eye in laevoversion
Congenital paresis of left superior rectus, motor adapted condition
REASONS FOR AHP
TO ACHIEVE BSV :
Head turned into the field of action of paralysed muscle
Eyes directed by DOLL’S HEAD PHENOMENON
Patient’s limited field of single vision coincides with his
egocentric position
Occurs when patient fixates with normal eye
TO ACHIEVE WIDE SEPARATION OF DIPLOPIC
IMAGES
In patients with no useful field of vision
Turn the head opposite to the field of paretic muscle
Deviation of the eye maximum
Occurs when patient fixates with affected eye
DOLL’S HEAD PHENOMENON
Aka tonic movements
Influenced by labyrinthine reflex from otoliths
When head is rotated to the right,the eye will rotate to the left and vice-versa
If the head is tipped backward, the eyes will rotate downward and vice-versa
ALSO KEEP IN MINDWhen head is tilted to the
right shoulder, right eye
intorts while left eye
extorts…..and vice - versa
LET’S TALK ABOUT
ISOLATED MUSCLEPALSY
IN HORIZONTAL RECTUS PALSY
Only one component of abnormal head posture i.e face/head turn
Face turn towards the action of paretic muscle
Head turn to right : - to maintain an ocular posture of laevoversion -compensate for defective abduction of RE or defective adduction of LE
To conclude,
Esotropic eye is made more esotropic
Exotropic eye is made more exotropic, BUT, BE CAREFUL It’s not true in case of cyclovertical
muscle
Head turn in case of cyclovertical muscle
Head is turned such that eyes are brought away from field in which muscle has its greatest vertical effect.
Right superior rectus palsy
e.g. for vertical rectus , having maximum effect on abduction,face is turned so that involved eye is adducted
i.e face is turned towards the affected eye
WHILE , for oblique muscles, having
maximum effect on adduction , face is turned such that the involved eye is abducted
i.e face is turned away from affected eye
IN PALSY OF CYCLOVERTICAL MUSCLE
Has all 3 components of abnormal head posture i.e chin elevation or depression , face turn and head tilt
CHIN ELEVATION
As chin is elevated , eye moves down
Occurs to maintain eye posture of depression to compensate for defective elevation of eye(s)
To conclude , hypotropic eye is eye is made more hypotropic
CHIN DEPRESSION
In chin depression , eye moves up
Adopted to maintain ocular posture of elevation to compensate for defective depression of eye(s)
To conclude hypertropic eye is made more hypertropic
HEAD TILT
In paresis of oblique muscle, head tilt occurs to compensate the torsion
caused by the direct antagonist of paralysed muscle
E.g.in RSO palsy,head tilt occurs to the left to compensate for the extorsion caused by RIO muscle
To conclude, extorted eye is made more extorted and intorted eye made more intorted BUT,its not true for vertical rectus muscle
In paresis of vertical rectus muscle , head tilt occurs to compensate the
torsion caused by contralateral anatagonist of the paralysed muscle
E.g in paresis of RSR, head tilt occurs to right to compensate for the extorsion of the left eye caused by overacting LIO muscle
To conclude,head is tilted to the side of hypotropic
eye
Muscle paralysed
Chin Face turn Head tilt
RSR elevation right right
RIR depression right left
RSO depression left left
RIO elevation left right
RLR _ right _
RMR _ left _
Muscle paralysed
chin Face turn Head tilt
LSR elevation left right
LIR depression left right
LSO depression right right
LIO elevation right right
LLR _ left _
LMR _ right _
EASY STEPS
1. Know the action of the muscle
2. Know the position of the eye
3. Know what should the head and chin do to keep the eye in that position or to make the eye more tropic(or other reasons discussed earlier)
EXAMPLES.. LEFT
LATERAL RECTUS PALSY
ACTION
OF LR
EYE POSITION
TO MAKE MORE ESOTROPIC
HEAD TURN TO
THE LEFT
LEFT MR
PALSYACTION
OF MR
EYE POSITION
TO MAKE MORE EXOTROPIC
HEAD TURN TO
THE RIGHT
Face turn to right to compensate palsy of left medial rectus
IN LSO PALSY ACTION OF
LSO
EYE POSITION
EXTORTED
ELEVATED
ADDUCTED
HEAD TILT TO
THE RIGHT
CHIN DOWN
FACE TURN
TO RIGHT
Left SO palsy,head turn with tilt in right side
Upshoot of LE due to contracture of LIO
Parallelism of visual axes in laevo-version
LIR PALSY ACTION OF IR
MUSCLE
EYE POSITION
ELEVATED
INTORTED
ABDUCTED
CHIN DOWN
HEAD TILT TO RIGHT
FACE TURN
TO LEFT
Compensatory head posture in RIR ,face turn to right,head tilt to left and chin depressed
Dextroversion showing depression of left eye
Dextrodepression,defective movement of RE with overaction of LSO
RSR PALSYACTION OF SR
MUSCLE
EYE POSITION
DEPRESSED
ABDUCTED
EXTORTED
FACE TURN
TO RIGHT
CHIN UP
HEAD TILT TO RIGHT
FIXING WITH NORMAL EYE FIXING WITH
PARETIC EYE
RSR palsy, chin elevation, head tilt to right with face turn to right(common occurrence)
RSR palsy, head tilt and face turn to the left (less common occurrence)
In primary position without head posture,LE hypotropic
In dextroversion ,parallelism of visual axes
Updrift of right eye in laevoversion
Congenital paresis of left superior rectus, motor adapted condition
LIO PALSYACTION OF IO
MUSCLE
EYE POSITION
INTORTED
ADDUCTED
DEPRESSED
FACE TURN
TO RIGHT
HEAD TILT TO LEFT
CHIN UP
LEFT INFERIOR OBLIQUE PALSY
-HEAD TILT TO LEFT-FACE TURN TO RIGHT-CHIN ELEVATED
Mnemonics for head turn and tilt in superior rectus and superior oblique palsy
SO U RS
SUPERIOR OBLIQUE
SAME SIDE
UNAFFECTED SIDE
sUPERIOR RECTUSTHIS HEAD POSTURE IS ADAPTED TO MAINTAIN BSV
LEFT SO PALSY
LEFT SR PALSY
ISOLATED VARIETIES OF OCULAR PALSY
Most common muscles to be paralysed singly : superior oblique and lateral rectusWHY ?
?
BECAUSE THEY HAVE SEPARATE
NERVE SUPPLY
In case of MR, IO, SR and IR
Supplied by 3rd cranial nerve, less likely to occur isolated muscle palsy…
total 3rd nerve palsy3rd nerve palsy partial 3rd nerve palsy
Note: in both cases pupil may or may not be spared in total palsy : both division involved in partial : only one division involved in isolated muscle palsy : only one muscle
involved
TOTAL 3RD NERVE PALSY
Extraocular (IR, MR, IO and SR) , LPS muscle as well as intraocular muscle (sphincter pupillae and ciliary muscle) affected
Dilated pupil Complete
loss of accomodati
on
ptosis
MOTOR ADAPTATION IN TOTAL 3RD NERVE PALSY
Occcurs only if pupil is spared so that the patient experience diplopia requires adaptation
Eye is turned down ,out and slightly intorted
SLIGHTLY CHIN UP FACE TURN
TOWARDS OPPOSITE
SIDE
HEAD TILT TO SAME
SIDE
PARTIAL 3RD NERVE PALSY
SUPERIOR DIVISION PALSY :
-SR and LPS muscle involved
-ptosis with hypotropic eye
- Chin elevated , face turn and head tilt to affected side
INFERIOR DIVISION PALSY :
-IR, IO and MR in addition to sphincter pupillae and ciliary muscle involved
-exotropic,intorted and hypertropic eye with pupil dilatation
-unlikely to be any field of binocular vision
-So , no need for AHP
Restriction of movement of LE in all gazes except in abduction
LEFT THIRD NERVE PALSY
Head tilt and face turn to right with chin up to avioid diplopia
DOUBLE ELEVATOR PALSY
Aka monocular elevation deficiency paralysis of both elevators of same eye i.e superior rectus and inferior oblique
elevation deficiency in entire upgaze i.e both upward adduction and abduction
Head posture
Eyes made more hypotropic by doll’s head phenomenon i.e chin is elevated
DOUBLE DEPRESSOR PALSY
Aka monocular depression deficiency
both depressors of same eye i.e inferior rectus and
superior oblique are paralysed
depression deficiency in entire downgaze both in
adduction and abduction
Head posture
Eyes made more hypertropic by doll’s head phenomenon i.e chin is depressed
SPECIAL RESTRICTIVE DISORDERS
Disorders that are non –paralytic but restricts the ocular movement
Caused by elements within orbit that either interfere with muscle contraction or relaxation or otherwise prevent free movement of globe
Examples ..
Duane’s retraction syndrome
Brown’s syndrome
Grave’s ophthalmopathy
Fibrosis of EOM
DUANE’S RETRACTION SYNDROME
there is fibrosis or inelasticity of the lateral rectus muscles and that the medial rectus muscle inserts abnormally far posteriorly myogenic cause
absent abducens nerve with anomalous innervations of the lateral rectus muscle by a branch of the oculomotor nerve,
Simultaneous activation of the medial and lateral rectus muscles the cause of globe
(neurogenic ) retraction
there is fibrosis or inelasticity of the lateral rectus muscles and that the medial rectus muscle inserts abnormally far posteriorly myogenic cause
absent abducens nerve with anomalous innervations of the lateral rectus muscle by a branch of the oculomotor nerve,
Simultaneous activation of the medial and lateral rectus muscles the cause of globe
(neurogenic ) retraction
AHP in DRS
Adopted to centralize BSV
Determined by deviation in primary posistion
ESOTROPIC : face turn to affected side EXOTROPIC : face turn to unaffected side
TYPE I DRS
Marked limitation of abduction
Normal or slightly defective adduction
Narrowing of PFH on adduction
Widening of PFH on abduction
TYPE II DRS
Marked limitation of adduction
Normal or slightly defective abduction
Narrowing of PFH on adduction
DUANE’S RETRACTION SYNDROME,TYPE II
Head posture to compensate for left medial rectus paresis
Dextroversion , defective adduction of LE and narrowing of PFH of LE
Laevo version, parallelism of visual axis, slight widening of left PFH
TYPE III DRS
Marked limitation of adduction and
abduction
Narrowing of PFH on adduction and
abduction
BROWN’S SYNDROME
Aka superior oblique tendon sheath syndrome
Apparent/pseudo paralysis of inferior oblique muscle, limitation of elevation in adduction
Due to restriction of IO action by an overly taut superior oblique tendon of the same eye
Widening of PFH on adductionFew may have in primary
position responsible for head
posture
hypotropia
AHP in BROWN’S SYNDROME
Head tilt to affected side
Face turn to contralateral side
Chin elevation head posture confined to chin elevation
if syndrome is bilateral
GRAVE’S OPHTHALMOPATHY
May be associated with hyper, hypo or euthyroidism
Circulating thyroglobulins, and anti thyroglobulin immune complex bind to EOM ophthalmopathy
in sequence of I’M SLOWInferior rectusMedial rectus Superior
rectusLateral rectus
Oblique muscles
Common ocular mobility defect is U/L elevator deficiency followed by defective abduction
eye is hypotropic and esotropic
Chin elevation
with or without
Face turn to same
side
FIBROSIS OF EOMs
Group of congenital anomalies with restrictions of EOMs
Due to replacement of muscle fibres by the fibrous tissue
Ranges from isolated fibrosis to B/L involvement of all EOMs
GENERALIZED FIBROSIS SYNDROME
Fibrosis of all EOMs no elevation or depression little or no horizontal movementBilateral ptosisAHP : backward head tilt with chin elevated
STRABISMUS FIXUS
Rare disorder , commonly with marked esotropia associated with extreme tightness of MR muscle
Most patient adopt chin elevation
VERTICALLY INCOMITANTHORIZONTAL HETEROTROPIA
Aka alphabet patterns tropiasHorizontal deviation that change in
magnitude with upgaze and downgaze
A-PATTERN HETEROTROPIA
Increasing convergence in upgaze and increasing divergence in downgaze
For A-pattern esotropes,to make eyes relatively convergent in downgaze,the chin is elevated
For A-pattern exotropes,to make eyes relatively divergent in upgaze,the chin is depressed
V-PATTERN HETEROTROPIA
Increasing convergence in downgaze and increasing divergence in upgaze
For V-pattern exotropes,to make eyes relatively convergent in upgaze,the chin is elevated
For V-pattern esotropes,to make eyes relatively divergent in downgaze,the chin is depressed
INFANTILE ESOTROPIA
Manifest eso deviation with an onset between birth and 6 months of age
Etiology unknown
Head & face tilt towards the shoulder of the fixating eye
In some cases AHP associated with ML nystagmus Pt turn head towards the side of the fixing eyewhich
gets optimal visual acuity in the position of adduction
Congenital esotropia with manifest nystagmus,
left eye fixing in adduction, head turned towards left, the direction of the left fixing eye ; pre op
Post-op picture after bi-lateral medial rectus recession
no head turn
REFERENCES
Practical orthoptics in the treatment of squint ; T.KEITH LYLE
and KENNETH C.WYBAR
Squint by LYLE ;eighth edition
Orthoptics and squint;A.K KHURANA
Binocular vision and ocular motility by Von norden
Diagnosis and Management of Ocular Motility Disorders by
Alec M. Ansons and Helen Davis
INTERNET
SPECIAL THANKS TO :
Sanjeev Bhattarai sir
THANKYOU ….