• Diplopia is the perception of double vision.
• Diplopia is classified as either binocular, which resolves when the patient covers either eye or monocular, which persists when the non-affected eye is covered.
  • Monocular diplopia indicates a problem intrinsic to the affected eye, whereas binocular diplopia indicates misalignment of the eyes.
  • 85% of diplopia is binocular.
• Diplopia may be secondary to a relatively benign cause such as refractive error or indicate a serious underlying pathology such as a brainstem stroke, MS, brain tumours, or botulism.
• Monocular diplopia is almost never a neurologic problem and results from distortions to the light path in the affected eye. The most common causes include keratoconjunctivitis sicca (dry eyes), cataracts, corneal irregularity and rarely retinal irregularities.
• Binocular diplopia results from misalignment of the eyes and most commonly arises from CN VI, III or IV palsies, with other causes including oculomotor muscle dysfunction, systemic disease processes or CNS lesions.

Recommendations

• Diplopia should be characterized as either: monocular or binocular, horizontal or vertical, acute or progressive, painful or painless, traumatic or non-traumatic and isolated or associated with other neurological signs.
  • True sudden onset suggests an ischemic/vascular cause.
  • Eye pain is associated with inflammation/infection
  • Concerning neurological features include focal neurodeficits, headache, meningismus or fever
• Mandatory physical exam components include:
  • Assessment of the 6 cardinal movements of gaze.
  • Facial examination looking for ptosis, pupillary asymmetry (i.e mydriasis)
• Possible adjunctive investigations include:
  • Fundoscopy for papilledema.
  • Slit Lamp Examination

CLICK TO ENLARGE

Monocular Diplopia

• Monocular diplopia is commonly caused by keratoconjunctivitis sicca (dry eyes), cataracts, corneal irregularity and rarely retinal irregularities.  After a slit lamp examination, patients can be referred to an ophthalmologist and discharged safely.

Binocular Diplopia

Concerning Neurological Deficits

• If neurological deficits are isolated to the brainstem (dysarthria, dysphagia, central vertigo), then assume stroke until proven otherwise. Activate your hospital’s stroke protocol and consult a neurologist for possible brainstem stroke.
• If diplopia is associated with neurological symptoms outside of the brainstem, consider work-up for other causes of diplopia discussed below.

Isolated CN VI, IV or III Palsies

CN III Palsy

• The eye is “down and out”, abducted and looking inferiorly. Usually presents with mydriasis and ptosis. Requires immediate CT and CTA to rule out a compressive aneurysm, most commonly at the junction of the posterior communicating and internal carotid arteries. Failure to identify a compressive aneurysm may lead to SAH and death.
• The absence of mydriasis (a.k.a “Rule of the Pupil”)is not a sensitive way to r/o a compressive aneurysm.

CN IV Palsy

• Vertical/torsional diplopia with near normal eye movements. Worst when looking down and toward the nose. Usually caused by decompensation of a congenital CN IV palsy, trauma or microangiopathic changes. Non-urgent referral to ophthalmologist is recommended.

CN VI Palsy

• Inability to abduct the affected eye, often with severe pain localized around the eye with the abduction defect. If this is an isolated, unilateral neurological finding with the presence of vascular risk factors, neuroimaging is typically unrevealing and non-urgent referral to an ophthalmologist is appropriate with spontaneous resolution of this palsy over 10-12 weeks. If the deficit lasts beyond 3 months, an urgent MRI brain should be obtained to rule out non-microvascular causes.
• An isolated CN VI palsy in a child requires an urgent MRI of the brain because nerve compression is the most common cause of an isolated CN VI palsy in the pediatric population.
• Bilateral CN VI palsies suggest more ominous etiologies such as ICH, subdural hematoma and brainstem infarcts.

• If ocular motility appears to be from multiple ocular motor nerves, it is reasonable to order a semi-urgent MRI of the cavernous sinuses/orbits with semi-urgent referral to Ophthalmology/Neurology. In the absence of any other neurological signs, it is safe for the patient to wait to see a specialist who is able to do a complete ocular alignment and motility workup.

Traumatic Diplopia

• Obtain NCCT Head and Orbits to rule out petrous apex fracture.

Mechanical Orbitopathy/Myositis

• Signs include proptosis, periorbital swelling, edema, conjunctival hyperemia or unilateral palpebral swelling.
• Causes include:
  • Graves orbitopathy causing enlargement/fibrosis of extraocular muscles. (Typically have previous diagnosis of hyperthyroidism and present with eyelid retraction, chemosis, conjunctival injection and proptosis)
  • Traumatic/Inflammatory/Neoplastic Mass Effect
• Obtain a Contrast-Enhanced MRI of the orbits +/- brain.

Cavernous Sinus Infection/Mass/Vasculitis

• Can affect CN III, IV and VI simultaneously and typically affects CN VI first (orbital apex syndrome).
• Causes:
  • Carotid-cavernosus fistula
  • Infectious/Inflammatory: GCA, Tolosa Hunt syndrome, Herpes Zoster Ophthalmicus
  • Tumor/Invasive Dx: (Lymphoma, Sarcoidosis)
  • Iatrogenic: Intravascular injection or diffusion of anesthetic into pterygoid venous plexus.

Other Causes

Myasthenia Gravis

• 60% present with ptosis/diplopia and fluctuating muscle weakness that worsens with eye movements in any cardinal direction of gaze. Associated symptoms include proximal muscle weakness, SOB or difficulty swallowing If suspected, semi-urgent referral to neurology is recommended, without need for CT scan.
  • Ice Test – Apply ice to patient’s closed eye and hold for 5 minutes, improvements in ptosis/diplopia suggest reversal of acetylcholine receptor blockade.

Wernicke’s Encephalopathy

• Diplopia associated with ataxia and altered mental status in a patient with chronic ETOH use or bariatric surgery. If suspicion for Wernicke’s Encephalopathy, treat empirically with IV thiamine infusion.

Botulism

• Gradual onset of dysarthria, dysphagia and double vision with foodborne exposure. May also have autonomic dysreflexia or pupillary dysfunction. Hospitalize immediately and monitor for any signs of respiratory compromise. Can consider intubation if the airway is at risk.

Multiple Sclerosis

• Internuclear Ophthalmoplegia, (inability to adduct the eye with nystagmus of the contralateral eye), along with optic neuritis (blurred vision and eye pain). Obtain MRI imaging and consult neurology.

Giant Cell Arteritis

• Uncommon cause of diplopia, associated with 2.7% of isolated sixth nerve palsy with no other systemic symptoms or signs. Obtain CBC and ESR in all patients 60+ with recent onset of diplopia. Urgent consultation to ophthalmology, as the patient may require temporal artery biopsy and/or initiation of high-dose systemic corticosteroids.

1. Chapter 18 of Rosen’s Emergency Medicine: Concepts  and Clinical Practice 9th Edition

   
   

2. Approach to a Patient with Diplopia in the Emergency Department (Margolin 2018).

   
   

3. Do patients with neurologically isolated ocular motor cranial nerve palsies require prompt neuroimaging? (Volpe et al 2014)

   
   

4. Incidence and Etiologies of Acquired Third Nerve Palsy using a Population-Based Method (Fang et al. 2017).

   
   

5. CanadiEM Podcasts: Episode 209 – Diplopia