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Incomitant Squint

Apr 25, 20252 min read

Incomitant ( paralytic ) Manifest

Characters:Z

  • usually acquired

  • Secondary angle > Primary angle

  • Angle of deviation varies in different directions.

  • Limitation of movements

  • Binocular diplopia

  • Abnormal head posture

  • False projection

  • Diplopia is maximal when attempting to look in the direction requiring the action of the weak muscle.

  • This type of strabismus may indicate either a nerve palsy or an extra-ocular muscle disease .

Palsies

  • 3rd nerve: failure of adduction, elevation and depression of the eye, ptosis and in some cases dilated pupil.
  • 4th nerve: defective depression of the eye when in adduction.
  • 6th nerve: Failure of Abduction.
  • Combination of ms palsy: -Ophthalmoplegia (Total & external) -SOF syndrome (3 &4&6&ophthalmic n) -Orbital apex syndrome (As SOF+ON)

Causes

  • Isolated nerve palsies
  • Trauma
  • Lesions affecting the EOM’s or CN’s especially no. III
  • Systemic dis- DM, stroke, botulism ,Thyroid dis

Causes of isolated nerve palsies

  • Vascular disease (DM, HTN, Aneurysm, CST)
  • Orbital disease
  • Trauma
  • Neoplasia
  • Raised intracranial pressure (3rd or 6th , False localizing)
  • Inflammation ( Sarcoidosis, Vasculitis, Infections, GBS) …

CST: Cavernous Sinus Thrombosis GBS: Guillain-Barre Syndrome

Extraocular muscles disease

  • Dysthyroid eye disease
  • Myasthenia gravis
  • Ocular myositis
  • Ocular myopathy
  • Browns Syndrome
  • Duane’s Syndrome …

Dysthyroid eye disease

  • Due to infiltration of the extraocular muscles with lymphocytes and the depositions of glycosaminoglycans.

  • Both Hyper and Hypo-Thyroidism.

  • The inferior rectus is the most commonly affected.

  • Mechanical limitation of the eye in up gaze.

  • Involvement of the medial rectuslimitation of abduction. (DDx6th nerve palsy)

  • Treatment:

    • Systemic steroids.
    • Radiotherapy.
    • Surgical orbital decompression.
    • Prisms.

Myasthenia Gravis

  • Acetylcholine receptor targeted antibodies

  • Females > males, 15-50 years of age

  • 40% show involvement of Extraocular muscles only.

  • Variable diplopia and ptosis due to fatigue.

  • Diagnosis: Edrophonium test

  • Treatment: neostigmine ( acetylcholine esterase inhibitor), thymectomy.

Concomitant Manifest

Types:

  • Convergent (esotropia)
  • Divergent (exotropia)
  • Vertical (hypertropia & hypotropia
  • Mixed

Each type can be classified to

  • Primary
  • Secondary
  • Consecutive

Graph View

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