Approach to Diplopia

Differential diagnosis

• Inflammatory
  • Multiple sclerosis
  • Giant cell arteritis
  • Mononeuritis multiplex
  • Miller-Fischer syndrome
• Eye movement defects (CN III, IV or VI)
  • Orbital apex (III, IV, VI plus ipsilateral II and V₁)
  • Cavernous sinus (III, IV, V₁, V₂, VI, sympathetic fibres to eye)
  • Base of skull (VI, IX)
  • Posterior communicating artery aneurysm (III)
  • Cerebellopontine angle (VII, VIII and VI if severe)
  • Midbrain (Weber’s syndrome – III and contralateral hemiparesis)
  • Pontine (Millard-Gubler syndrome – VI, ipsilateral VII and contralateral hemiparesis)
  • Pontine (inter-nuclear ophthalmoplegia or one-and-a-half syndrome)
  • Raised intracranial pressure (bilateral VI)
  • Leptomeningeal disease
• Neuromuscular
  • Myasthenia gravis
  • Lambert-Eaton myasthenic syndrome
• Orbital pathology
  • Thyroid eye disease
  • Orbital / peri-orbital cellulitis
  • Neoplastic infiltration
• Myopathy
  • Chronic progressive external ophthalmoplegia (CPOE)
  • Kearns-Sayre syndrome (CPOE + retinitis pigmentosa + complete heart block, ± ataxia)
  • Myotonic dystrophy
• Endocrine
  • Diabetes mellitus
  • Acromegaly
  • Graves’ disease
  • Pituitary tumour (lateral extension into cavernous sinus / hemi-field slide)
• Progressive supranuclear palsy
• Migraine with ophthalmoplegia
• Trauma
• Ocular
  • Retinal detachment
  • Diabetic retinopathy
  • Central retinal vein / artery occlusion
  • Vitreous haemorrhage
  • Cataract

Questions to ask

• Does the double vision go away when you cover either eye?
  • Binocular diplopia: correction when either eye is covered
  • Monocular diplopia: correction when the affected eye is covered (=ocular pathology)
• Is the double vision horizontal or vertical?
  • Horizontal diplopia: lateral / medial rectus (unilateral / bilateral VI or INO)
  • Vertical diplopia: superior / inferior rectus, superior / inferior oblique (III or IV)
• Is the double vision worse on looking in any particular direction?
  • Diplopia is maximal in the direction of action of the paretic muscle
• Myasthenia gravis
  • Does the severity of the double vision fluctuate?
    • Myasthenia gravis gets worse as the day goes on, and with activity, e.g. reading
  • Can be improved by resting the eye
  • Do you cough when you swallow?
  • Do you fall asleep easily in the day / have you ever fallen asleep when driving?
• Has anyone told you that your eyes appear different or bulging?
  • Thyroid eye disease
  • Orbital tumour
  • Carotid-cavernous fistula
• Do you have a headache?
  • Giant cell arteritis: jaw claudication, scalp tenderness
  • Migraine: hemicranial, throbbing, may have aura, nausea, hemiplegia
  • Meningitis: photophobia, neck stiffness
• Demyelination / optic neuritis
  • Do colours appear as vibrant as usual? (optic neuritis)
  • Is there any eye pain or redness?
  • Have you noticed any weakness or numbness?
• Symptoms of thyroid disease
  • Do you ever feel your heart is beating very quickly?
  • Have you noticed the weather being unusually hot lately?
  • Have you noticed your hands trembling?
  • Have your periods been irregular or more heavy than usual?
  • Have you been having any diarrhoea?
• Osmotic symptoms
  • Do you wake up in the middle of the night to pass urine?
  • Do you feel you are drinking more water than usual?
  • Have you been losing weight?

Things to examine for

• Inspection
  • Ptosis
  • Lid retraction
  • Proptosis / exophthalmos
  • Strabismus
  • Peri-orbital swelling
  • Goitre / thyroid surgery scars
  • Parkinsonism
• Pulse – rate, regular / irregular (hyperthyroidism)
• Eyes
  • Acuity
    • Finger-counting
    • Red desaturation
  • Pupils
    • Equal (Horner’s may produce unequal pupils)
    • Consensual reflex
    • Relative afferent pupillary defect
  • Extra-ocular movements (in which direction is the diplopia maximal)
    • Convergence if INO detected – should be normal
  • Fatigability
• Pronator drift (brainstem syndromes)
• Upper limb fatigability
• Thyroid status
  • Pulse
  • Tremor
  • Goitre – smooth / diffuse / nodular
  • Displaced apex beat
  • Murmurs
  • Lung bases for pulmonary oedema
  • Legs for pre-tibial myxedema / peripheral oedema

Investigations

• Blood tests
  • Thyroid function tests
  • Thyroid receptor antibody if Graves’ disease
  • Fasting blood glucose
  • Erythrocyte sedimentation rate (giant cell arteritis)
• Myasthenia gravis
  • Antibodies against nicotinic acetylcholine receptors
    • If negative and high index of suspicion: muscle-specific kinase antibodies
  • Tensilon test
    • Improvement in weakness with edrophonium
  • Repetitive nerve stimulation
    • Measures neuronal response to repeated stimulation. Indicative of myasthenia if decrement in response observed.
• Imaging (if cranial nerve palsy present)
  • Computed tomography / magnetic resonance imaging of the brain

Patient concerns

• Will it get better?
  • Should get better with treatment of underlying cause
  • Can refer to ophthalmology colleague in the meantime to help with aids to minimize diplopia
• Driving: should not drive until diplopia is corrected
• Occupation
• Inheritance

Management

• Multidisciplinary
  • Visual aids: e.g. patches to cover either eye, prisms
  • Referral to therapists for adaptation to monocular vision while treating underlying cause
  • Referral to neuro-ophthalmologist
  • Referral to specialist in underlying condition
• Treat underlying cause