Diplopia is nearly always binocular, with movement of one eye being limited for a number of possible reasons. Although relatively uncommon as a presenting symptom, the majority of causes are significant and therefore careful assessment is essential.
- Physiological (Focusing too Near, or Perceiving Objects Nearer than those Focused on)
- Intoxication: Prescribed Sedation, Non-prescribed Drugs, Especially Excess Alcohol, Opiates, Benzodiazepines
- Mild Head Injury, Causing Temporary Diplopia
- Facial Bone Trauma: Orbital and Zygomatic Fracture
- Mononeuropathy (e.g. Diabetes, MS)
- Orbital Disease (Usually Associated with Pain and Proptosis) and after Surgery (Scarring Limiting Globe Movement)
- Guillain–Barré Syndrome
- Palsy of Third, Fourth or Sixth Cranial Nerves due to Intracranial Space-occupying Lesion (Haemorrhage, Tumour, Aneurysm, Abscess, Cavernous Sinus Thrombosis)
- Myasthenia Gravis
- Monocular Diplopia: Early Cataract, Irregularity of Corneal Surface (e.g. Post Trauma or Inflammation)
- Ophthalmoplegic Migraine
- Tolosa–hunt Syndrome: Granulomatous or Inflammatory Process in Anterior Portion of Cavernous Sinus or Superior Orbital Fissure
- Pseudoparalysis of Ocular Muscles: Dysthyroid Disease; Duane’s Syndrome (Congenital Fibrosis of Lateral Rectus)
- Orbital Myositis
- Pituitary Exophthalmos
Key distinguishing features of the most common diagnoses
|Physiological||Intoxication||Stroke||Head Injury||Facial Bone Trauma|
|History of Trauma||No||No||No||Yes||Yes|
|Unilateral Limb Paresis||No||No||Possible||Possible||No|
|Facial Bone Deformity||No||No||No||No||Yes|
Likely: none; FBC, ESR/CRP, lipid studies, urinalysis, fasting glucose or HbA1c.
Possible: TFT, X-rays, CT/MRI scan.
Small Print: Edrophonium test, EMG, CSF studies, angiography.
- No investigation is indicated in primary care for the most common causes – referral is the likeliest course of action.
- FBC, ESR/CRP, lipid studies: If stroke suspected and admission not required. FBC and ESR/CRP will also provide evidence of inflammatory conditions.
- Urinalysis for glucose/fasting glucose or HbA1c: To investigate possible diabetes.
- TFT will reveal hyperthyroidism.
- Other investigations (and possibly some of the above) are likely to be carried out in secondary care: Skull and facial bone X-rays in trauma cases; CT or MRI scan (head injury, stroke, MS, space-occupying lesion); specialist neurological investigations (edrophonium test, singlefibre EMG studies, CSF examination, angiography).
- Establish if the diplopia is binocular or not. Uniocular double vision has a much narrower differential diagnosis.
- Take time to clarify the symptom. Sometimes, patients complain of ‘double vision’ when they really mean blurring – and vice versa.
- The cover test is a reliable way to find out which eye is affected.
- Fourth cranial nerve palsy produces diplopia on looking downwards and inwards, often noticed when descending stairs. The patient may try to compensate by tilting the head – so-called ocular torticollis.
- Intoxication in conjunction with a head injury is commonly seen in custody medicine and A&E departments. Admission for neurological observation is strongly recommended.
- Diplopia of acute onset may well reflect serious pathology – refer for urgent assessment.
- Intermittent diplopia should not be dismissed too readily as insignificant – remember that myasthenia gravis and multiple sclerosis are possibilities.