Emergency department evaluation of diplopia is largely based on a comprehensive history and should always include the following questioning with documented findings:
Does the diplopia resolve by covering one eye? (Differentiates binocular diplopia (disappears when one eye covered; most common) from monocular diplopia (persists with one eye covered; usually related to a focal, ocular problem).
Does the degree of diplopia change with direction of gaze and/or head position? (Determines whether deficit related to cranial nerve innervation, helps localize associated paretic muscle).
Is the diplopia horizontal (i.e. two objects side by side) or vertical (i.e. two objects one on top of the other)? (Horizontal diplopia suggests cranial nerve III or VI deficit (i.e. lateral gaze function); vertical diplopia suggests cranial nerve IV deficit (i.e. elevator or depressor gaze function).
Is there associated pain? (Suggests possible foreign body or extraocular muscle entrapment).
Was there associated trauma? (Blow-out fractures can be associated with diplopia).
Is there associated weakness, headache, confusion, or dizziness? (Imaging usually indicated to rule out intracranial processes such as stroke or increased intracranial pressure).
