Non-Paralytic and Paralytic Strabismus

Professor K N Jha, MS

Email: kirtinath.jha@gmail.com

Strabismus

A condition in which

visual axes of the two

eyes do not meet at the

point of object of

regard.

Types

• Concomitant ( Non-paralytic)

• Incomitant strabismus (Paralytic)

Concomitant strabismus

The misaligned eyes maintain their abnormal

relationship in all directions of the gaze.

Etiology

• Defective vision in one eye: high refractive

error, media opacities or ocular disease

• Disturbance in muscle equilibrium: defective

development /malinsertion on EOM/s

• Change balance in accommodation and

convergence e.g. a hypermetrope

Types of comitant strabismus

• Latent (Phoria) Manifest (Tropia)

• Convergent Divergent

• Intermittent Constant

Comitant strabismus

Symptoms

- Asthenopia

- Cosmetic disfigurement

- Subnormal vision

-Refractive error

-Amblyopia

Convergent strabismus

• More common in hypermetropes and commences in

childhood

• More common than divergent variety

• May commence in childhood following a febrile illness

• Diminishes with age

• May have a cyclovertical element

• May be associated with neurological disorders

Divergent strabismus

• More common in myopes

• Often commences at a later age , particularly

after loss of vision in one eye

• Tends to increase with age

Signs

• Deviation of the eye/s

• Refractive error

• Amblyopia

• Suppression

• Eccentric fixation

Investigation

• History

-complaint

-onset and duration

-Previous treatment

-treatment goals and expectation

• Diagnostic tests

Diagnostic tests

• Visual acuity and fixation pattern

• Cycloplegic refraction and funduscopy

• Head posture and exam of ocular motility

• Details of ocular deviation

• Test of binocular vision

• Forced duction test

Management

• Evaluation of the case

• Parental education

• Spectacle correction

• Amblyopia therapy

• Orthoptic training

• Surgical treatment-

Strabismus with binocular vision -Without binocular vision

PARALYTIC SQUINT

Common cause of nerve palsies

• In children: Trauma, intrinsic tumors

• In young adults: Trauma , demyelinating

disease

• Older adult: Vascular lesion , tumors

Clinical features

Symptoms : Diplopia (binocular), vertigo

Signs:

• Strabismus

• Limitation of movement

• False orientation

• Compensatory head posture

• Changes in orbital tissues in long standing cases

• Primary deviation: deviation of the eye on the

affected side with normal eye fixing.

• Secondary deviation: Deviation of the normal

eye with affected eye fixing.

Compensatory head posture

• Face turn – Seen in cases of paralysis of

horizontally acting muscles

• Head tilt – Seen in cases of torsional deviations

• Chin elevation/depression – In vertical deviations

False projection

Demonstrated by closing patient’s normal eye

and telling him to point quickly at an object in

front of him

Investigation of a case of EOM palsy

• Evaluation of squint

• Identification of involved EOM or nerve

• Finding out etiology by

- history

-ocular examination

-Neurological examination

-Special investigations e.g. USG,CT,MRI

Treatment

• Treat the underlying cause

• Palliative treatment: prisms /occluder on the affected eye

• Permit time (At least 6 months) for spontaneous recovery.

• Botulinum toxin injection overacting antagonist of the paralyzed muscle

Features Paralytic Squint Non-paralytic squint

Deviation Different in different directions of gaze

Equal or constant in all directions of gaze

Diplopia Present Absent

Ocular movements

Restricted in the direction of action of the paralyzed muscle

Full in all directions of gaze

Cover test Secondary deviation > primary deviation

Primary deviation = secondary deviation

Compensatory head posture

Present Absent

Onset Usually sudden Usually gradual

Neurological findings

Common Uncommon

Vertigo & nausea Usually present Absent

Causes of uniocular diplopia -Subluxation of lens

-Incipient cataract

-Multiple pupils

-Large iridodialysis

Causes of binocular diplopia

-Paralytic squints due to neurological causes

-Restrictive myopathies

-Myasthenia gravis

-Anisometropic glasses

-After squint correction if abnormal retinal

correspondence is present

Points to Remember

• Etiology of nerve palsies

• Differences between paralytic and non-

paralytic squint

• Differences between uniocular and binocular

diplopia

• Visual problems of squint