Diplopia (double vision) can be the first, or the only, symptom of life-threatening disease such as expanding intracranial aneurysm, brain tumour, myasthenia gravis or giant cell arteritis. All patients with new-onset diplopia should, therefore, be urgently assessed and investigated.
A 23-year-old woman presented to her GP with a two-day history of painless horizontal double vision. She first noticed this problem while watching television, when she saw two television screens. The GP found her visual acuity to be 6/6 in each eye and the eyes looked well aligned. The pupils were the same size in each eye, there was no ptosis and eye movements appeared to be normal.
The GP referred the patient to an optometrist, who checked the patient’s eyes thoroughly and reported that no ocular disease was present. However, the optometrist suggested the GP perform a neurological assessment.