Strabismus (Squint)

Ophthalmic condition in which the eyes do not properly align with each other when focusing to look at an object (i.e. poor fusion)

Aetiology

  • Commonly onset is in childhood, can start in adulthood but this is less common
  • Can occur due to muscle dysfunction, farsightedness, problems in the brain, trauma or infections
  • Risk factors include premature birth, cerebral palsy and a family history of the condition

Clinical presentation

Symptoms

  • Misalignment of the eyes
  • Reduced visual acuity
  • Diplopia
  • Asthenopia (i.e. eye strain, fatigue or pain), particularly in the afternoon or at the end of the day
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Signs

  • Corneal reflections will be asymmetrical

Investigations

Cover test

  • The direction of movement tells you which type
    • Outward movement of eye → esotropia
    • Inward movement of eye → exotropia
    • Downward movement of eye → hypertropia
    • Upward movement of eye → hypotropia
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Management

  • Treatment depends on type of strabismus and the underlying cause; may include the use of glasses and possibly surgery
  • Strabismus not corrected in infancy can cause amblyopia (cortical blindness, 'lazy eye')
    • A wandering eye can often be corrected surgically, but not until a baby is old enough
    • In the meantime, cover the infant's good eye with a patch for a few hours each day so that the brain must rely on signals from the bad eye
    • This helps the brain develop properly to process signals coming from both eyes