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Squint

Specialties > Child health

Differential Diagnosis Schema 🧠

Types of Squint

  • Esotropia: Inward turning of the eye, common in infants; may be congenital or acquired.
  • Exotropia: Outward turning of the eye; may be intermittent or constant, often noticed when the child is tired.
  • Hypertropia: Upward turning of the eye; less common, usually associated with paralysis of the superior oblique muscle.
  • Hypotropia: Downward turning of the eye; rare, often associated with trauma or cranial nerve palsies.
  • Intermittent squint: Squint that is not present all the time, often noticed when the child is tired or unwell.
  • Alternating squint: When the squint switches between the two eyes, indicating that both eyes have the potential for fixation.
  • Constant squint: Persistent misalignment of one eye, often leading to amblyopia (lazy eye).

Causes of Squint

  • Refractive errors: Uncorrected hypermetropia (farsightedness) leading to esotropia as the eyes over-accommodate to focus.
  • Congenital factors: Family history of strabismus, congenital cranial nerve palsies, or developmental disorders.
  • Neurological causes: Cranial nerve palsies (especially CN III, IV, VI), intracranial tumors, or raised intracranial pressure.
  • Trauma: Head or orbital trauma leading to cranial nerve damage or muscle entrapment.
  • Systemic conditions: Conditions like Down syndrome, cerebral palsy, or prematurity can increase the risk of strabismus.
  • Infectious causes: Rarely, infections like meningitis can cause cranial nerve palsies leading to squint.

Key Points in History 🥼

Onset and Duration

  • Age of onset: Congenital squints typically present within the first six months of life, while acquired squints may present later due to refractive errors or neurological issues.
  • Intermittent vs. constant: Intermittent squints may suggest refractive issues, while constant squints are more likely to lead to amblyopia.
  • Circumstances of onset: Consider any associated trauma, illness, or fatigue when the squint is first noticed.
  • Family history: A family history of squint or amblyopia can be relevant in assessing the risk and prognosis.

Associated Symptoms and Visual Concerns

  • Double vision (diplopia): Often present in acquired squints, suggesting a recent onset or neurological cause.
  • Head tilt or turn: Children may adopt an abnormal head posture to compensate for the squint and reduce diplopia.
  • Visual acuity: Reduced vision in one eye may indicate amblyopia, especially in the presence of a constant squint.
  • Eye pain or redness: May suggest an underlying ocular condition, such as uveitis or orbital cellulitis, contributing to the squint.
  • Neurological symptoms: Headache, nausea, vomiting, or signs of raised intracranial pressure should raise concerns about an intracranial cause.
  • History of refractive correction: Previous use of glasses or patching for amblyopia treatment can indicate the chronicity and management history of the squint.

Background

  • Past Medical History: Include a history of prematurity, developmental delays, neurological conditions, or previous ocular surgery.
  • Drug History: Consider medications that may affect neurological function or have ocular side effects (e.g., antiepileptics, steroids).
  • Family History: Include family history of squint, amblyopia, refractive errors, or other ocular conditions.
  • Social History: Assess the impact on schooling and social interactions, especially in children, as well as access to eye care services.
  • Birth history: Relevant in congenital cases; inquire about birth trauma, APGAR scores, and any neonatal complications.

Possible Investigations 🌡️

Ophthalmological Examination

  • Visual acuity test: To assess the level of visual impairment in each eye, critical for diagnosing amblyopia.
  • Cover test: Used to detect misalignment by observing eye movement when one eye is covered and then uncovered.
  • Hirschberg test (corneal light reflex test): To assess the angle of strabismus; an abnormal reflex suggests a squint.
  • Refraction test: To detect refractive errors that may be contributing to the squint, often performed under cycloplegia in children.
  • Fundoscopy: To rule out retinal or optic nerve pathology that could be contributing to vision loss or squint.
  • Ocular motility assessment: To check the full range of eye movements and identify any restrictions or nerve palsies.

Neurological Investigations

  • Cranial nerve examination: Particularly of CN III, IV, and VI to identify any nerve palsies contributing to the squint.
  • Neuroimaging (MRI/CT): Indicated if an intracranial mass, trauma, or other neurological cause is suspected, especially with acute onset or associated neurological symptoms.
  • Electromyography (EMG): Rarely used, but may be indicated if there is suspicion of myopathy or a neuromuscular junction disorder.
  • Visual field testing: Useful in detecting any associated defects that may indicate a neurological cause.

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Child health