The most important thing when assessing double vision is to rule out any sinister causes.

 History:

  1. Is the double vision monocular or binocular? (ie. does it go away when closing one eye?)
    • Monocular causes can be of refractive (ie. astigmatism), corneal (ie. pterygium, keratoconus) and ocular. Cataract and astigmatism are common causes for monocular diplopia.
    • If binocular: can be more serious causes (muscular, neurological or cardiovascular issues)
  2. How are the images aligned? horrizontal, vertical  or oblique. Using our two hands to demonstrate would make it easier for patients to understand .
    • Are they overlapped or far apart
  3. Onset? 
    • Is it sudden (more suggestive of cardiovascular event) or gradual (possible compression)
    • Is there a traumatic event associated with onset of diplopia? Orbital fracture can cause muscle entrapment.
  4. Constant or variable? Variability during the day, or heat? Fatigability?
    • Variability due to heat is associated with Multiple sclerosis
    • Fatigability can be a sign of Myasthenia Gravis.
  5. Comitancy: Does it go away or get worse when turning head in a certain direction?
  6. Any associated neurological signs and symptoms, such as headache, nausea, droopy lid, different pupil sizes?
  7. How is vision with current glasses?
  8. General health and medications: 
    • Cardiovascular conditions like diabetes and hypertension can cause aneurysm 
    • Cancer that can metastasise to the brain
    • Some common systemic conditions such as Thyroid Eye Diseases and Myasthenia Gravis can also cause diplopia


Assessments:

 Preliminary tests:
  1. Visual acuity (best corrected or pinhole)    
  2. Cover test in all nine gazes is needed to check for comitancy. Magnitude of deviation should also be assessed at both distance and near.
  3. Motility
  4. Colour vision and/or Red cap to check for Optic nerve function
  5. Confrontation can localise brain lesion
  6. Pupils: check for pupil sizes and especially RAPD (Relative Afferent Pupil Defect)


Lid position should be noted to identify droopy lid, exophthalmos and enophthalmos. Ocular globe displacement can give clues for possible compression.
Posterior eye assessment is a must to check for any optic nerve head swelling, optic atrophy, signs of compression.
Visual Field test should be done if neurological cause is suspected.

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