Double vision is an important symptom with a large number of possible causes. An accurate initial assessment is extremely helpful in assessing the urgency of the situation and determining the appropriate course of action.
- Monocular diplopia should be detected at an early stage because it is managed differently to binocular diplopia, with patients requiring ophthalmological (rather than neurological) referral.
- Eye movements should be assessed in an H-pattern.
- Diplopia is greatest when the patient looks into the field of action of the weak muscle (or muscles), with the most eccentric of the two images coming from the paretic eye.
- Straightforward palsies of the 3rd, 4th and 6th cranial nerves can usually be diagnosed clinically.
- Painful ocular motor nerve palsies should be treated as an emergency and referred immediately to exclude the possibility of intracranial aneurysm. This also applies to a sudden onset, pupil-involving third nerve palsy.
- If symptoms fluctuate over time, consider myasthenia gravis.
- If there is a history of trauma, consider an orbital blowout fracture and refer the patient immediately to an ophthalmologist.
- Patients with more complicated disorders will need formal neurological assessment.