PARALYTIC AND PARETIC STRABISMUS GENERAL FEATURES, IMPORTANCE OF HERINGS LAW, INVESTIGATIONS OF PARETC STRABISMUS

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Presenter Pabita Dhungel B.optometryInstitute of Medicine

References

1) BINOCULAR VISION & STRABISMUS –GK VON NOORDEN

2) CLINICAL MANGEMENT OF STRABISMUS- ELEZABETH E.CALAROSSA & MICHAEL W. ROUSE

3) AAO- SECTION: PEDIATRIC OPHTHALMOLOGY & STRABISMUS

4) STRABISMUS SIMPLIFIED- PRADEEP SHARMA5) PRACTICAL ORTHOPTICS IN THE TREATMENT OF

SQUINT- LYLE AND JACKSON’S

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PRESENTATION LAYOUTIntroduction to extra ocular musclesFew related terms• Introduction to paralytic and paretic strabismusClassificationClinical characteristicsImportance of Herings lawInvestigations of paretic strabismusSummary

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Introduction

There are 6 extraocular muscles – 4 rectus muscles, 2 oblique muscles

5 muscles arise from the apex of the orbit, the inferior oblique arises form the inferonasal angle of the orbit

The 4 recti muscles originate form the apex of the orbit at the level of the Annulus of Zinn

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Contd....The recti muscles are inserted in front of the ocular equator, the

obliques are inserted behindMovements occur about 3 primary axes around the centre of

rotation – the vertical, horizontal and saggital axesThe action of a muscle depends on the angle of its plane and

the anterio-posterior axis of the eye. It follows that the action of the muscle may vary according the

positions of the globe in the orbit.

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Few related termsAgonist= muscle producing a specific ocular movement

Antagonist= muscle having the opposed actionSynergist = muscle having the same actionsIpsilateral = on the same sideContralateral = on the opposite sideContracture = increased resistance against passive

stretching of the muscle, loss of elasticity

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Hering’s Law of Equal Innervation An equal and simultaneous innervation flows from

the brain to a pair of muscles of both eyes (yoke muscles) which contract simultaneously in different binocular movements

Eg. Equal and simultaneous innervation flows to:

1.RLR and LMR muscles during dextroversion

2.Both MR during convergence

3.RSR and LIO muscles during dextroelevation

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Sheringtons Law of Reciprocal Innervation concerned with the co-ordination of muscle pairs of one eye.

ie the contraction of each ocular muscle is accompanied by a simultaneous and proportional relaxation of its antagonist.

e.g. during dextroversion , an increased innervational flow to the RLR and LMR is accompanied by decreased flow to the RMR and LLR muscle

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Sequelae of Ocular Muscle PalsyUnderaction of the primary affected muscleOveraction of the contralateral synergistOveraction of the ipsilateral (direct) antagonistUnderaction of the antagonist of the contralateral synergist

(contalateral antagonist)Overaction of the ipsilateral synergist??

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Overaction of the contralateral synergist always present. This overaction occurs when the affected eye is fixing as

a result of increased innervation being required to rotate the affected muscle into its field of action.

Due to Herings Law an overstimulation of the contralateral synergist follows

This is always the largest overaction in the sequelae.

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Overaction of the ipsilateral (direct) antagonist can lead to a permanent contracture of the muscle and a

loss of elasticityIf the patient fixes with the non-involved eye within a few

days a contracture will develop in the direct antagonist muscle

because the normal contracture of the direct antagonist is unopposed by the weak muscle.

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Underaction of the antagonist of the contralateral synergist (contalateral

antagonist) with the involved eye fixing, the movement of the eye

into the field of action of the weak muscles antagonist requires less innervation than normal due to the contracture.

Therefore less innervation is supplied to the contralateral antagonist which under-acts

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For example in paralysis of the right superior rectusunderaction of right superior rectusoveraction of the left inferior obliqueoveraction of the right inferior rectusunderaction of the left superior oblique(overaction of the right inferior oblique)

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Introduction to paralytic strabismus

Terms paretic and paralytic often are used interchangeably in clinical ophthalmology

Paralytic strabismus is an incomitant strabismus due to motor deficiency of one or a group of extra ocular muscles

Incomplete paralysis is called paresis and complete deficiency is called paralysis, while palsy is used for both without specifying

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ClassificationA). Neurogenici) supranuclear ii) nucleariii) internucleariv) infranuclear- fascicular ( Main nerve trunk or subdivision) oculomotor nerve (III CN)Trochlear nerve (IV CN)Abducens nerve (VI CN)

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Contd...B. Myogenic i) nerve muscle junction lesion (myasthenia)ii) muscle(a) Congenital Absence ,hypoplasia mal insertion or musculofascial

anomalies(b) Traumatic laceration, disinertion(c) inflammatory (myositis)(d) Orbito- myopathies(e) Dystrophy01/03/15

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Causes of neurogenic lesions1. congenital2. traumatic3. inflammatory4. neoplastic5. ischemic6. toxic7.Demyelinating disease8. idiopathic

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Paralytic strabismus etiologyI. Neurogenic lesions1. Congenital hypoplasia or absence of nucleus: third

and sixth cranial nerve palsies.2. Inflammatory lesions: encephalitis,meningitis,

neurosyphilis,peripheral neuritis (viral),infectious lesions of cavernous sinus and orbit.

3. Neoplastic lesions. 4. Vascular lesions:HTN, DM and atherosclerosis. haemorrhage, thrombosis, embolism, aneurysms or vascular occlusions.

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Contd…5. Traumatic lesions: head injury6. Toxic lesions:carbon monoxide poisoning, effects of

diphtheria toxins (rarely),alcoholic and lead neuropathy.

7. Demyelinating lesions:multiple sclerosis II. Myogenic lesions1. Congenital lesions. These include absence,hypoplasia, malinsertion, weakness and musculofacial

anomalies.2. Traumatic lesions.

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Contd…3. Inflammatory lesions: Myositis (viral) , influenza,

measles.4. Myopathies:These include thyroid

myopathy,carcinomatous myopathy,Progressive external ophthalmoplegia

III. Neuromuscular junction lesionIt includes myasthenia gravis.

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Paralytic strabismusSYMPTOMS:

1. LIMITATION OF OCULAR MOVEMENTS2. SUDDEN ONSET OCULAR DEVIATION3. DIPLOPIA4.CONFUSION5. NAUSEA , VERTIGO

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Diplopia

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DIPLOPIA-A)Uncrossed diplopia with an

esotropia. B)Crossed diplopia with an exotropia.

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SIGNS Limitation of movement in the field of action of the

muscleDifference in primary and secondary deviationsCompensatory HPFalse projection

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Clinical characteristicsi) incomitance variable ocular deviation in different position

which is maximum in the field of action of the muscle (eg. In a LLR palsy esotropia is maximal in the abduction of LE)

ii)Limitation of movement of the eye in the field of action of the EOM( in

LLR palsy the abduction of the LE is deficient or limited)

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Contd...iii) difference in primary and secondary deviation deviation of the squinting eye with normal eye fixing

is called primary deviationDeviation of the normal eye with the paretic eye

fixing is called secondary deviationIn paralytic strabismus secondary deviation is greater

than primary deviation

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Contd...This is because the paretic eye requires more effort

to straighten (come to the primary position to take up fixation) and this extra effort is passed on to the contralateral synergist, which is normal, increasing the ocular deviation

The reverse is true for spastic strabismus i.e primary deviation is greater than the secondary deviation

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differences Paralytic comitant

Age of onset Usually late Usually early childhood

Type of onset Sudden Gradual, sudden manifestation

Precipitating events

Usually head injury , systemic illness

Rarely present. Even if present no cause effect relationship

Associated neurological signs

May be present None

Comitance May develop in late stages Usually present (except in extreme gazes)

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Differences Paralytic Comitant

Diplopia Usually present Absent

Head posture Usually present Absent

Cyclotropia Usually present (except with horizontal muscle palsy)

Absent exception associated A.V. patterns or oblique over-actions

Sensory adaptions( suppression- amblyopia ARC)

Rare Frequent

Past pointing Present in recent cases absent

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Stages of paralytic squintUndergoes three stages1. Paresis of the particular muscle2. Overaction of the ipsilateral antagonist3. Underaction of the antagonist of the

contralateral synergist

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1. First stageThe maximal deviation is in the field of action of

the paretic muscle for e.g. In a case left LR palsy, the deviation is maximum in levoversion

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2. Second stageAs the overaction of the ipsilateral antagonist

occurs the deviation overacting, the duration increases in the dextroversion

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3. Third stageThe underaction of the contralateral synergist

occurs.this is known as inhibitional palsy

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Importance of hering’s law1. Secondary deviation( fixating with squinting eye) is more than primary deviation in paralytic strabismusThis is based in hering’s law because when the patient

fixates with the squinting eye an excess innervation is required to the paralysed muscle to fixate and the

concomitant excess supply to the yoke muscle from the normal eye causes excess contraction leading to more, the so-called secondary deviation

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Contd…2. Inhibitional palsy of the contralateral antagonist muscle developing in patients with paralytic squint is based on Hering’s law for e.g if a patient has RSO muscle paresis and fixates with RE on object located on patient’s left, less innervation of RIO is required to move the eye in this gaze, because it doesn’t have to overcome the normal antagonistic effect of RSO muscle

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Third nerve palsyThe III nerve divides into two branches. The superior branch supplies the LPS and SRThe inferior branch supplies the MR, IR and IO

muscles. A complete lesion of the III nerve involving both

branches will result in a deficit of elevation, adduction and depression in abduction. There will be an accompanying ptosis and pupil

dilatation

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Contd...AetiologyLocalisation of lesionNuclearNuclear III often produces bilateral defects of ocular

motility and lid function. The levator palpebral superioris muscles share a

common central nucleus that producesClinical Orthoptics, Third Edition. Fiona J. Rowe.C 2012 John Wiley & Sons, Ltd. Published 2012 by Blackwell Publishing Ltd.

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Neurogenic disorder A nuclear lesion may also result in the following: Unilateral III with bilateral ptosis Unilateral III with contralateral superior rectus

underaction Isolated extraocular muscle palsy of inferior rectus,

inferior oblique or medialrectus muscles (Brown 1957) Bilateral III with spared levator function (Biousse & Newman 2000, Saeki et al. 2000).

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Internuclear

Internuclear ophthalmoplegia Weber’s syndrome: III and contralateral hemiplegia

due to lesion of corticospinal tract Benedikt’s syndrome: III and contralateral ataxia and

intension tremor Claude’s syndrome: Lesion of the red nucleus and III

nucleus producing anipsilateral III nerve palsy and contralateral ataxia

(Broadley et al. 2001)

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Infranuclear

Third nerve palsy may be central, sparing the pupil or peripheral with pupil involvement.

If the pupil is spared, the cause is most likely vascular.

When the pupil is involved, the cause is likely to be an

aneurysm (Goldstein&Cogan 1960). However, pupil sparing in children (unlike inadults) may not be helpful in differentiating the causes

of the palsy and third nerve01/03/15

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InvestigationVisual acuity It is necessary to lift the ptotic lid to evaluate visual

acuity.May be reduced due to mydriasis, particularly for near

visual acuityCover test An exo- and hypo-deviation is present

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Ocular motilityThere will be limited elevation, depression and

adduction,which may be complete or partial limitations, depending on the extent of paresis/palsy.

The examiner should always check for the presence of IV nerve function by asking the patient to attempt to look down and outwards and observe for the presence of incyclotorsion during this movement.

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Contd…In case of presence of ptosis the upper lid will have

to be raised by the examiner (or an assistant) in order to

perform the ocular motility assessment. It is important to check for unilateral versus bilateral

signs and extent of limitations (ductions) versus version movements.

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Right 3rd nerve palsy

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Investigation Hess chart The affected eye will show a markedly constricted

field whereas the other eye demonstrates overaction of its

muscles

Diplopia There will be constant diplopia unless complete

ptosis is present and blocks the vision of the affected eye.

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Hess chart of right 3rd nerve palsy

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Convergence This will be absent if the medial rectus muscle is

paralysed.Binocular functionThis is usually absent unless the III nerve paresis is

mild and partial.Accommodation If the underlying cause of the lesion has resulted in

pupillary dilatation, then fibres to the ciliary body are also likely to be involved so that accommodation will be defective.

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Aberrant regenerationchange in the actions of muscles supplied by the third

nerve due to regrowth of damaged nerve fibres following complete or severe third nerve palsy

(Shuttleworth et al. 1998).

It is liable to occur when either trauma or an aneurysm

has caused the lesion (Cox et al. 1979, Rossillion et al. 2001).

May occur from weeks to months after the onset of the III nerve paresis.

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InvestigationCover test Combined horizontal and vertical deviations are

common.Ocular motilityAbnormal movements often involve the eyelids and

pupils. There may be horizontal gaze and lid synkinesis (Chua et al. 2000)

Limited elevation and depression with globe retraction on attempted vertical movements or ipsilateral adduction on attempted elevation or depression.01/03/15

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Contd…Ptosis The lid may rise on attempted depression, adduction

and occasionally abduction (pseudo-Graefe phenomenon).

Pupil This may constrict on attempted adduction, elevation

and depression(pseudo-Argyll Robertson pupil).Convergence This may occur on attempted elevation

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Cyclic oculomotor palsyThis rare condition is usually congenital and

unilateral in origin (Burian & Van Allen 1963).

It is often associated with a partial III nerve palsy with some degree of ptosis.

Acquired cyclic ocular motor palsy may occur following irradiation of the skull base and is similar to ocular neuromyotonia

(Miller & Lee 2004).

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Contd…It may also be due to a compressive lesion (Bateman & Saunders 1983).

The condition is described as having cyclical fluctuation in two phases:

1. Paralytic phase: There is a partial III nerve palsy.2. Miotic phase: There is convergence, lid retraction,

accommodation and pupil constriction.

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Single muscle palsy1. Medial rectus This produces an exo-deviation, which is greater for

near fixation.2. Inferior rectus: This produces hyper- and exo-deviation3. Superior rectus: This is often bilateral and may present with a V exo

pattern.4. Inferior oblique: This is a feature of an A eso pattern 01/03/15

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Differential diagnosis of single muscle palsiesMR palsy : Atypical Duane’s retraction syndrome :Uni/bilateral internuclear ophthalmoplegiaIR palsy: Myogenic (myasthenia gravis) : Mechanical limitation (thyroid eye disease) : Trauma (blowout fracture)IO palsy: Brown’s syndromeSR palsy : Trauma (blowout fracture) : Mechanical limitation (thyroid eye disease)

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Double elevator palsyThis often has a congenital origin and is presumed to

be caused by a supranuclear defect. The superior rectus and inferior oblique muscles of

the same eye are affected (Jampel & Fells 1968, Strachan & Innes 1987).

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InvestigationCover test There is a hypo-deviation in the primary position that

may be manifest or latent.Ocular motilityThere is limited elevation of one eye in both

adduction and abduction.Ptosis and/or pseudoptosis may be present. Bell’s phenomenon is usually present.Abnormal head postureThe chin is elevated to compensate for the palsy

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Contd…Binocular functionIf there is only a small angle of deviation in the

primary position, this may be controlled with or without an abnormal head posture, resulting in a latent hypo-deviation.

In these circumstances, binocular single vision is present.

Forced duction testThere may be full passive movement (negative result)

or it may be positive, depending on cause that is important for surgical planning

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Differential diagnosis double elevator palsyThe following conditions should be differentiated

from double elevator palsy as they will have a positive forced duction test:

Blowout fracture Thyroid eye disease Brown’s syndrome Congenital fibrosis of the inferior rectus muscle General fibrosis syndrome

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IV (fourth) cranial nerveThe IV cranial nerve supplies the superior oblique

muscle only. Any lesion affecting the nerve may result in

difficulties of depression, incyclorotation and abduction of the eye

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AetiologyLocation of lesionFourth nerve palsy may be due to lesions in the

nucleus or fascicular lesions of the midbrain. It can be difficult to differentially diagnose nuclear

and fascicular lesions as the IV nerves decussate immediately after exiting the nuclei and exit the

dorsal midbrain after a very short intra-midbrain course.

The IV nerve is not only susceptible to damage as it exits the midbrain but also is vulnerable in the cavernous sinus and orbital apex.

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Contd…congenital or acquired. Acquired group may be caused by the following: Trauma: Particularly bilateral cases, as the IV cranial nerve is

the only nerve to arise from the dorsal surface of the midbrain, and therefore follows a long, winding route that renders it susceptible to injury.

Vascular, for example hypertension. Diabetes. 01/03/15

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Contd…Space-occupying lesions.In congenital superior oblique palsy, the tendon is

usually lax and abnormally long

(Plager 1990, Plager 1992).

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Investigation Case history In congenital cases, the patients are often affected

bilaterally. They may present with any of the following:1. Manifest strabismus without binocular function2. Binocular function, but there may be an abnormal

head posture, depending on the extent of paresis

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Contd…There is often facial asymmetry in congenital superior

oblique palsy consisting of shallowing of the midfacial region between the lateral canthus and the edge of the mouth (Parks 1958).

This is found in three-fourth of patients with congenital palsy (Wilson &Hoxie 1993, Paysee et al. 1995).

In acquired cases, the paresis may be unilateral or bilateral.

Bilateral case is often associated with major closed head trauma.

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Contd…Symptoms of cyclovertical diplopia are experienced,

which worsen on downgaze. The presence of an abnormal head posture tends to indicate more long-standing deviations.

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Abnormal head postureIn unilateral IV nerve paresis, the patient may present

with chin depression with face turn and head tilt away from the affected side.

Bilateral cases demonstrate chin depression but there may well be no face turn or head tilt unless one side is affected more than the other.

Persistent abnormal head posture following surgery for IV nerve palsy should be investigated to exclude sternocleidomastoid muscle

tightness that may have developed in congenital cases (Lau et al.2009).

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Cover testThe test is performed with and without the abnormal

head posture for comparison. A latent deviation exists if a compensatory abnormal head posture is adopted. When the test is repeated with the head straight, the

deviation will increase and may become manifest

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Contd…The affected eye shows a hyper-deviation and an

associated esodeviation.(However, an exo-deviation may be seen if this waspresent before the onset of the palsy.) It is useful to note that the vertical deviation is

commonly greater on near testing than for distance. In bilateral cases, the main deviation usually tends to

be a small-angle horizontal deviation.

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Ocular motilityThe primary underaction of the affected superior

oblique muscle results in a number of sequelae. There is overaction of the contralateral inferior rectus

and of the ipsilateral inferior oblique muscles. The contralateral superior rectus shows secondary

underaction.The combination of these muscle effects is variable

and often depends on whether or not the deviation is long standing

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Left 4th nerve palsy

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Contd…In bilateral cases, a V pattern is often present. In the presence of this, one should always suspect a

bilateral case, especially where there is an excyclotorsion of greater than 7 and a tendency◦

towards reversal of any hyper-deviation or diplopic images on lateral gaze

(Hermann 1981).

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Contd…Convergence This may be reduced, either due to convergence

insufficiency or the vertical deviation. Differentiation is achieved by correcting the

deviation and seeing if convergence improvesField of binocular single visionThe area in which binocular single vision is retained is

displaced upwards to the affected side

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DiplopiaThe patient experiences a greater degree of diplopia

on near testing when looking down. The diplopia is vertical and usually uncrossed.However, if an exo-deviation is present, the

horizontal element of diplopia will be crossed

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Binocular functionAssessment of binocular function is carried out with

and without the abnormal head posture, if one is present.

Binocular single vision cannot be maintained if there is a significant degree of torsion and therefore is often not present in acquired bilateral palsies.

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Contd…Patients who maintain binocularity tend to have a

small angle of deviation associated with a congenital palsy.

Some patients with long-standing acquired palsies can maintain binocularity if there is a good fusional control with an extended vertical fusion range

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B/L asymmetrical 4th nerve palsy

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Torsion Diagnostic prismsExcyclotorsion is frequently present in acquired

bilateral cases.Fresnel prisms may be used temporarily to correct the

angle of deviation. If the prism alleviates the need for an abnormal head posture, then the indication is that the IV nerve was

responsible for the abnormal head posture rather than a non-ocular cause

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Differential diagnosisthyroid eye disease, ocular surgery, orbital

fracture, neurosurgery, childhood strabismus, skew deviation, third nerve palsy, myasthenia gravis and decompensated hyperphoria (Tamhankar et al. 2011).

Typically, excyclotorsion is seen in IV nerve palsy and incyclotorsion is seen in skew deviation.

Furthermore, the deviation in IV nerve palsy remains when the patient is lying down whereas skew deviation resolves on lying down (Wong 2010).

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Investigations unilateral bilateral

Cover test Hyper-deviation in primaryposition reflects extent of palsy

Often only slight hyper-deviation in primary position

Ocular motility No reversal of hypertropia orand diplopia on lateral versionsSlight V pattern may be noted

Reversal of hyper-deviationdiplopia on lateral versionsLarge V pattern

Abnormal head posture

Chin depression, head tilt andhead turn

Chin depression

Torsion Slightly extorsion Extorsion >10◦

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VI (sixth) cranial nerveThe VI cranial nerve supplies the lateral rectus muscle

only. A lesion affecting the nerve will result in defective

abduction of the eye.

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AetiologyThe commonly recognised causes of sixth nerve palsy

include space-occupying lesions, trauma, vascular insults and inflammation.

Sixth nerve palsy secondary to raised intracranial pressure is also commonly regarded as a typical false localising sign.

Other causes have included pseudotumor cerebri (idiopathic intracranial hypertension), post-operative complications, viral infection, multiple sclerosis and otitis

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Contd…Congenital Following birth trauma Hereditary Infection (maternal) Failure of lateral rectus developmentAcquiredThis differs according to age: Children (Afifi et al. 1992):– Space-occupying lesions– Infections, bacterial or viral- trauma

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Contd…– Raised intracranial pressure– Decompensated esophoria– Infantile esotropia with cross-fixation– Mobius syndrome– Duane’s retraction syndrome Young adults:– Trauma– Space-occupying lesions– Post-viral inflammation

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Contd…●– Multiple sclerosis– Diabetes– High myopia– Ophthalmoplegic migraineOlder adults:– Vascular– Diabetes– Space-occupying lesions– Senile lateral rectus weakness

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InvestigationCase history Birth history may be significant. The patient may complain of horizontal diplopia,

which is worse in the distance and/or on lateralgaze and relatives or friends may notice the presence of

squint (esodeviation) or an abnormal head posture

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Contd…Visual acuity This may be reduced if the affected eye fails to fixate

properly due to the presence of a marked deviation. Amblyopia will develop in children with unilateral

strabismus.Abnormal head postureThe face is turned towards the affected side.

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Contd…Cover test An eso-deviation is present that is often greater on

distance testing.The test should be carried out with and without an

abnormal head posture, if one is present. The deviation increases without the head posture but

does not necessarily become manifest

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Contd…Ocular motilityThe primary underaction of the affected lateral rectus

results in limited abduction and is followed by a number of sequelae.

There is overaction of both the contralateral and ipsilateral medial recti.

There is also secondary underaction of the contralateral lateral rectus

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Rt 6th nerve palsy

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Contd…Binocular functionThis is often retained in the presence of an abnormal

head posture.As the angle of deviation is often smaller for near

fixation, binocular function is usually present on near fixation.

In cases of head trauma, fusion may have been lost.

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Rt 6th nerve palsy

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Differential diagnosisDuane’s retraction syndrome, Infantile esotropia, Nystagmus block syndrome Medial wall fracture

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Thank you !!!