Perspectives on migraine: prevalence and visual symptoms.
About 20 per cent of women and 10 per cent of men experience migraine at some time in their lives, of whom about one half to two thirds will have had a migraine attack in the previous 12 months. Prevalences of this order have been found in a survey of patients in an Australian optometric practice. Between one third and one half of migraineurs experience sensory or motor aura. Visual aura are by far the most common of the aura. A high proportion (more than 40 per cent) of migraineurs presenting for routine optometric examination will not have had their headache or aura formally diagnosed. Optometrists can give reassurance by providing a formal diagnosis and, when appropriate, they can refer their migraine patients to sources of advice on how the frequency and severity of their attacks might be ameliorated. The diagnosis of migraine is straightforward when the migrainous episode and any associated aura follow a classical pattern. However, diagnosis is often challenging, especially for aura occurring without headache, when the aura are atypical, when the first attack of migraine occurs after the age of 50 years, when there are persistent visual field losses or when there are pupillary anomalies or extra-ocular muscle palsy and diplopia associated with the migraine. Unusual presentations must be approached with care, using a good knowledge of the diversity of migraine, careful history taking and a thorough ocular and visual examination. As visual field losses can be associated with migraine and migraine may be a risk factor for low-tension glaucoma, visual field examination is often indicated for patients with a history of migraine. In some cases of migraine, referral for neurological work-up will be necessary before concluding that the headache and visual symptoms can be attributed to migraine.