Red flag symptoms: Diplopia

Red flag symptoms in presentations of double vision (diplopia), possible causes and questions to ask patients.

Horner's syndrome is one of a range of possible causes of diplopia (SPL)
Horner's syndrome is one of a range of possible causes of diplopia (SPL)
  • Persistent headaches
  • Changes in pupillary size
  • Drooping of the eyelids
  • Ocular fatigue on excessive use
  • Loss of vision
  • Existing neurological symptoms, such as weakness of arm, face, or leg, or dysphasia
  • Excessive alcohol history
  • Protruding eyeballs
  • History of recent facial trauma

Diplopia or double vision is not a common presentation in primary care. However, it is important to be aware of and recognise the common conditions that may present with this symptom.

Diplopia may be found as a result of a systemic review or feedback from an optician or hospital.

It is very important to establish what the patient means by double vision, how it is affecting their life and whether they drive a vehicle. Most patients tend to have researched their symptoms on the internet, so understanding their ideas, concerns and expectations of the problem is also important.


It is vital to establish:

  • What does the patient mean by double vision?
  • How long have they been experiencing it?
  • How is it affecting them?
  • Have they noticed any other change in their vision?
  • Have they recently visited an optician?
  • Have they experienced this before and if so, what was the outcome of any consultations they may have had?
  • Have they noticed any change to their pupil?
  • Have they noticed any new squints?
  • Have their eyelids started to droop?
  • Have they noticed any tiredness associated with the eyes?
  • Are there any associated headaches? If so, it is important to establish the cause of the headache.
  • Have they noticed any weakness of the arm, face or leg?
  • Have they noticed any scalp tenderness or pain on chewing?
  • Have the eyeballs changed in shape or size?
  • A systemic review may be necessary, depending on the answers to the previous question. It will probably be clear if there has been a history of facial trauma.
  • Has the patient started any new medication? Smoking, drug and alcohol history may be relevant.
  • What does the patient think is causing the problem?
  • How does this symptom affect them day to day?
  • Do they drive?


Examination needs to be focused on the history. Inspect the eyelids and the pupils. Is there any obvious drooping or discrepancy in size of the pupils? Is there any obvious cranial nerve palsy? Look for proptosis.

Check visual acuity - ensure you have a Snellen chart. It may be necessary to see if the pupils are equal and to check reaction to light and accommodation. Check the range of eye movements.

If relevant, a more detailed neurological examination may be necessary. You may need to check for temporal artery tenderness.

A history of facial trauma may result in examination of the facial bones to exclude an orbital floor fracture.

Investigations in primary care

  • Blood tests, including ESR and TSH and fasting glucose/HbA1c
  • Plain chest X-ray if Horner's syndrome is suspected
  • Outpatient CT/MRI head - this will not be available to all GPs, so refer to your local rules.

Dr Singh is a GP in Northumberland

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This is an updated version of an article that was originally publised in October 2014.

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