NON-CONCOMITANT STRABISMUS

INTRODUCTION

•Strabismus is the Misalignment of one or both eyes so as the eye (eyes) is not looking straight at the object of regard.

•It is also known as SQUINT

Significance In Children

•Children need normally aligned eyes to develop vision.

•Strabismus in childhood is the second most common presentation of retinoblastoma.

•Strabismus is a common presentation for refractive errors.

Significance in Adults

•Frequent sign of neurological disease•Frequent presentation of systemic disease •( Thyroid disease & Myasthenia)•Cosmetology

Strabismus secondary to loss of vision from Cataract in Lt. eye

Types of Eye Movements

•Horizontal direction•Vertical direction•Torsional direction

All superior muscles are intortors.All inferior muscles are extortors

Anatomy & PhysiologyMuscle Nerve Function Testing

MR 3rd Nasal Look to nose

LR 6th Temporal

Look away

SR 3rd Elevates, intorts ADDucts

Up and out

IR 3rd Depress, extorts, ADDucts

Down and out

Anatomy and PhysiologyMuscle Nerve Functio

nTesting

Superior Oblique

4th Intorts, depress, abducts

Look Down & In

Inferior Oblique

3rd Extrorts, elevates, abducts

Look Up & In

CLASSIFICATION

•Apparent strabismus or pseudo strabismus

•Latent squint or Heterophoria•Manifest squint or Heterotropia• 1. Concomitant squint• 2. Non concomitant squint

Types of Strabismus

•Esodeviation eye turned in

•Exodeviation eye turned out

•Hyperdeviation eye turned up

•Hypodeviation eye turned down

Classification of Strabismus

•Constant or intermittent•Latent or manifest (phoria or tropia)•Unilateral or alternating•Comitant or incomitant (restrictive or

paralytic)•Paralytic or non-paralytic•Nuclear or supranuclear

Esotropia

Esotropia

Alternating Esotropia

Exotropia

Causes of Strabismus•Congenital: Imbalance between

innervations and contraction

•Refractive errors

•Loss of vision•Paralysis or Neuromuscular•Restrictive: Thyroid eye disease•Tumours

Presenting symptoms of Strabismus•Deviation of the eye (cosmesis)•Double vision•Torticollis (abnormal head posture)

•Unexplained visual loss in a normal looking eye (Microtropia)

Abnormal Head Posture

Non- concomitant Strabismus

•Also known as incomitant strabismus or manifest squint

•This is a type of heterotropia in which the amount of deviation varies in different directions of gaze

Non comitant squint

•This includes the following conditions•Paralytic squint•A and V pattern heterotropias•Special Ocular motility defects

Paralytic strabismus

•This is ocular deviation due to complete or incomplete paralysis of one or more extra-ocular muscles.

•ETIOLOGY•Neurogenic lesions•Myogenic lesions•Lesions at the level of the neuro-muscular

junction

NEUROGENIC LESIONS• Congenital: Hypoplasia or absence of

nucleus causing palsies of the CN III and VI. Birth injuries also mimic congenital lesions.

• Inflammatory lesions: Due to encephalitis, meningitis, neurosyphilis or peripheral neuritis (viral) or infectious lesions of cavernous sinus and orbit.

• Neoplastic lesions: Brain tumours involving nuclei, nerve roots or intracranial part of the nerves and intraorbital tumours involving peripheral parts of the nerves.

NEUROGENIC LESIONS•Vascular lesions: seen in hypertension,

diabetes mellitus, atherosclerosis in the form of haemorrhage, thrombosis, embolism, aneurysms or vascular occlusions. Cerebro vascular accidents are common in elderly.

•Traumatic lesions: Head injury and direct or indirect trauma to the nerve trunks.

•Toxic lesions: carbon monoxide poisoning, diphtheria toxins effect, alcohol and lead neuropathy.

NEUROGENIC LESIONS

•Demyelinating lesions: Ocular palsy may occur in multiple sclerosis and diffuse sclerosis.

MYOGENIC LESIONS•Congenital lesions: absence, hypoplasia,

malinsertion, weakness and musculofacial anomalies.

•Traumatic lesions: laceration, disinsertion, haemorrhage into the muscle substance or sheath and incarceration of muscles in fractures of the orbital walls.

•Inflammatory lesions: Myositis is usually viral in origin and may occur in influenza, measles and other viral fevers.

MYOGENIC LESIONS

•Myopathies: Thyroid myopathy, carcinomatous myopathy, those due to drugs, progressive external ophthalmoplegia which is a bilateral myopathy of extraocular muscles which may be sporadic or inherited as an autosomal dominant disorder.

NEUROMUSCULAR JUNCTION LESION•Myasthenis gravis: This is due to fatigue

of muscle groups which usually starts with small extra ocular muscles before involving large muscles.

CLINICAL FEATURES•Diplopia: main symptom of paralytic

squint. It is more marked towards the action of the paralysed muscle. It may be

•Crossed: in divergent squint•Uncrossed: in convergent squint•Horizontal•Vertical or oblique depending on

paralysed muscle•This is due to formation of image on

dissimilar points of the two retinae.

CLINICAL FEATURES

•Confusion: this is due to formation of image of two different objects on the corresponding points of two retinae.

•Nausea and vertigo: These are due to diplopia and confusion

•Ocular deviation: occurs suddenly

CLINICAL SIGNS•Primary deviation: deviation of the

affected eye and is away from the action of paralysed muscle, e.g if the lateral rectus is paralysed the eye is converged.

•Secondary deviation: this is deviation of the normal eye seen under the cover when the patient is made to fix with the squinting eye.

•Restriction of the ocular movement: direction of the action of paralysed muscles.

CLINICAL SIGNS• Compensatory head posture: the patient does

this to avoid diplopia and confusion. Head is turned towards the direction of the action of the paralysed muscle, e.g if the right lateral rectus is paralysed the patient’s head will be turned right.

• False projection or orientation: this is due to increased innervational impulse conveyed to the paralysed muscle. It can be demonstrated by asking the patient to close the sound eye and then to fix an object placed on the side of paralysed muscle. Patient will locate it further away in the same direction. E.g. Patient with right LR paralysis will point towards right more than the object actually is.

A and V pattern Heterotropia• A and V pattern squint are labelled when the

amount of deviation in the squinting eye varies by more than 10 and 15 degrees respectively between upward and downward gaze.

• A and V esotropia: In A- the amount of deviation increases in upward gaze and decreases in downward gaze. It is vice versa in V esotropia.

• A and V exotropia: In A the amount of deviation decreases in upward gaze and increases in downward gaze and vice versa in V exotropia.

SPECIAL OCULAR MOTILITY DEFECTS•Duane’s retraction syndrome•It is a congenital motility defect occurring

due to fibrous tightening of lateral or medial or both rectus muscles.

•Limitation of abduction(type 1) or adduction(type 2) or both (type 3)

•Retraction of the globe and narrowing of the palpebral fissure on attempted adduction.

•Eye in primary position may orthotropic, esotropic or exotropic.

SPECIAL OCULAR MOTILITY DEFECTS•Brown’s superior oblique tendon

sheath syndrome•It is congenital ocular motility defect due

to fibrous tightening of the superior oblique tendon. It is characterized by limitation of elevation of the eye in adduction(normal elevation in abduction), usually straight eyes in primary position and positive forced duction test on attempts to elevate eye in adduction.

SPECIAL OCULAR MOTILITY DEFECTS•Strabismus fixus• This is a rare condition characterised by

bilateral fixation of eyes in convergent position due to fibrous tightening of the medial recti.

•Double elevator palsy•This is a congenital condition caused by

third nerve nuclear lesion. It is characterised by paresis of the superior rectus and the inferior oblique muscle of the involved eye.

Management of Strabismus

History:4 most important questions:1.Age of onset 2.Constant or intermittent3.Unilateral or alternating4.Diplopia or torticollis

Management of Strabismus

Examination:Three objectives:1. Confirm the diagnosis

2. Diagnose type of strabismus

3. Differentiate paralysis from no paralysis

DIFFERENCE BETWEEN PARALYTIC AND NON-PARALYTIC STRABISMUSPARALYTIC SQUINT NON -PARALYTIC SQUINT

• Onset is sudden• Diplopia present• Ocular movt is limited in

direction of actin of paralysed mzl.

• False projection is positive • Head posture depends on

the presence of muscle paralysed.

• Nausea and vertigo are present

• Secondary deviation is more than primary deviation

• In old cases pathological sequelae in mzls are present

• Onset is slow• Diplopia is absent• Full ocular movt• False projection is

negative• Head posture is normal• Nausea and vertigo are

absent• Secondary deviation is

equal to primary deviation• In old cases pathological

sequelae in mzls are absent.

Examination of Strab Patient

1. Simple observation for the nasal white of the eye

2. Corneal light reflex

3. Cover test

METHODS OF EXAMINATION• Inspection: Large degree squint

(convergent or divergent)• Ocular movements: Both uniocular as well

as binocular movements should be tested in all cardinal positions of gaze.

• Pupillary reactions: may be abnormal in patients with secondary deviations due to diseases of retina and optic nerve.

• Media and fundus examination: may reveal associated disease of ocular media, retina or optic nerve.

METHODS OF EXAMINATION•Testing and refractive error: this is the

most important because a refractive error may be responsible for the symptoms of the patient or for the deviation itself. Preferably, refraction should be done under full cycloplegia especially in children.

•Cover test: Direct will confirm the presence of manifest squint.

•Alternate will reveal whether the squint is unilateral or bilateral

METHODS OF EXAMINATION

•Estimation of angle of deviation•1. Hirschberg corneal reflex test•2.Prism and cover test•3. krimsky corneal reflex test•4.Measurement of deviation with

synoptophore Tests for grade of binocular vision and

sensory functions1.Worth’s 4-dot test2.Test for fixation

METHODS OF EXAMINATION

•4. After image test•5. Sensory function test•6. Neutral density filter test

ADDITIONAL METHODS OF INVESTIGATION•Evaluation for squint•1. Diplopia charting•2. Hess/Lees screen test•3. Field of binocular vision•4. Forced duction testInvestigations to find out the cause of

paralysis•5. orbital ultrasonography •6. orbital and skull CT scan•7. Neurological investigation

DIPLOPIA CHARTING•This is indicated in patients complaining of

confusion or double vision. The patient is asked to wear red and green diplopia charting glasses. Red glass-right eye, green-left eye. In a semi-dark room, he is shown a fine linear light from about 4 ft and asked about the images in primary position and in other positions about gaze. Patients tells about the position and seperation of the 2 images in different fields.

Hess screen test

•Shows paralysed muscles and the pathological results of paralysis like overaction, contracture and secondary inhibitional palsy. When the two charts are compared, the smaller chart belongs to the eye with paretic muscle and the larger to the eye with overacting muscle.

HESS CHART

Field of binocular fixation

•This can be used in patients with paralytic squint where applicable, so if the patient has some field of single vision. This test is performed on the perimeter (with the central chin test)

Forced Duction Test

•This is done to differentiate between the incomitant squint due to paralysis of extraocular muscle and that due to mechanical restriction of the ocular movements.

•FDT is positive(resistance encountered during passive rotation) in cases of incomitant squint due to mechanical restriction and negative in cases of extraocular muscle palsy.

TREATMENT• Treatment of the cause• Conservative measures: wait and watch for

self improvement for 6 months, vit.B-complex as neurotonic and systemic steroids for non-specific inflammations

• Treatment of annoying diplopia using occluder on the affected eye with intermittent use of both eyes with changed head posture to avoid suppression ambylopia.

• Surgery, in case recovery does not occur in 6 months is done to provide a comfortable field of binocular fixation i.e. Central fields and lower quadrants. To strengthen the paralysed muscle by resection and weakening of the overacting muscle by recession.

SURGICAL TREATMENT

•Procedures that change the direction of muscle action

•a) vertical transposition of horizontal recti to correct A and V patterns

•b) posterior fixation suture (Faden Operation) to correct dissociated vertical deviation

•c) transplant of muscles in paralytic squints

REFERENCES

•www.wikipedia.com•www.eyedoctor.com•www.eyecare.com•Ophthalmology by A.K.KHURANA 3rd

edition

THANKS FOR YOUR ATTENTION