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Probability diagnosis


  • Ocular nerve palsy (3,4,6) various causes


  • Ophthalmoplegic migraine

  • Physiological (disparateness)

  • Drug effect e.g. alcohol, benzodiapines


  • Eye disorder e.g. cataract, refractive error, cornea

Serious disorders not to be missed




  • Intraocular abscess

  • Sinusitis

  • Botulism



  • Involving 3, 4 or 6 cranial nerves


  • Facial bone trauma/head injury

  • Guillain-Barré syndrome

Pitfalls (often missed)

Any orbital infiltration


  • Multiple sclerosis

  • Myasthenia gravis

  • Orbital myositis

  • Cavernous sinus thrombosis

  • Wernicke’s encephalopathy

Masquerades checklist

Diabetes: mononeuritis

Drugs e.g. sedatives, opioids, alcohol

Thyroid/other endocrine: hyperthyroid

Is the patient trying to tell me something?

A consideration if nil findings. Some cases are idiopathic.

Key history

A careful history is required to determine nature of diplopia: if one or both eyes, intermittent, constant or associated pain. Check for other neurological symptoms incl. other cranial nerve dysfunction, and other associated general symptoms such as weight loss and fever. Check past medical history incl. diabetes, hypertension and cerebrovascular disease, as well as drug history, esp. alcohol or illicit, prescription and OTC drugs.

Key examination

  • General features: appearance of patient, vital signs

  • Inspection of the eyes and neck (goitre)

  • Ocular motility

  • Visual acuity

  • Establish if binocular or monocular

  • Perform the cover test

  • Cranial nerves in general

  • Other basic neurological examination

  • Ophthalmoscopy

Key investigations

Nil for most cases

First line:

  • urinalysis

  • blood sugar

  • FBE



  • TFTs

  • imaging if indicated (refer)

Diagnostic tips

Refer urgently if diplopia is binocular, of recent onset and persistent. Other ‘red flags’ incl. any pupil involvement, pain, proptosis, any other neurological symptoms or signs.

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