Diplopia - ED evaluation

Primary eye disorders or systemic diseases presenting as ophthalmologic complaints may present to the Emergency Department especially when symptoms are acute in onset. Diplopia is one such complaint which we might come across in ED. 

Key Questions when evaluating diplopia:
1. Is it Monocular or Binocular Diplopia?

• Monocular Diplopia - Eye Problem (cataract irregularities, lens displacement, or primary problems with the corneal curvature such as keratoconus.)
• Binocular Diplopia (Common) - Likely Neuro Problem (3,4,6 Nerve lesions, Grave's eye Disease, Myasthenia gravis, Orbital Myositis)

2.  Does the degree of diplopia change with direction of gaze and/or head position?  (Determines whether deficit related to cranial nerve innervation)

3. Is the diplopia horizontal or vertical?  

(Horizontal diplopia suggests cranial nerve III or VI deficit (i.e. lateral gaze function); vertical diplopia suggests cranial nerve IV deficit (i.e. elevator/depressor gaze function).

4. Associated pain? (Suggests possible foreign body or extraocular muscle entrapment).

5. Associated trauma? (Blow-out fractures can be associated with diplopia).

6. Associated weakness, headache, confusion, or dizziness?  (Imaging usually indicated to rule out intracranial processes such as stroke or increased intracranial pressure).

3rd Nerve palsy

• Supplies most of the EOM
• Lesion results in Down and out deviation of eyeball, Ptosis due to levator palpebrae paralysis and Ptosis due to damage to parasympathetic pupil-constrictor fibers from the Edinger-Westphal nucleus

Most third nerve palsies are caused by ischemic events due to hypertension or diabetes. 

Pupillary involvement is a crucial diagnostic sign -- compressive lesions tend to involve the pupil, while vascular lesions might actually spare it! This is due to the fact that the parasympathetic nerves course along the surface of the oculomotor nerve making them susceptible to compressive lesions from the outside whereas ischemic lesions occur deeper within the oculomotor nerve and thus spare the superficial parasympathetic fibers.


4th Nerve Palsy

• Difficult to diagnose
• Innervates Superior Oblique muscle
• These patients have an upward deviation of the affected eye with a tilt their head away from the lesion
• Possible Causes include Trauma, ischemia, congenital lesions, malignancy

6th Nerve Palsy

• Supplies the lateral rectus muscle
• Loss of function renders the eye unable to abduct (turn out). 
• Patients go cross-eyed, so to compensate they may turn their head to avoid double vision.
• Susceptible to high intracranial pressures.e.g. pseudotumor cerebri 

Table from Rosen's EM Textbook - Causes of Diplopia

Take Home

• Differentiate betweekn monocular and binocular diplopia is the key
• Think compressive causes e.g. P Comm Aneurysm with a dilated pupil (3N palsy)

Posted by:

              

     Lakshay Chanana

     

     ST4 Trainee

     Royal Infirmary of Edinburgh

     Department of Emergency Medicine

     Edinburgh

     Scotland

     @EMDidactic