Seeing Auras: Ocular Migraines
Eighty percent of people with migraines get disabling headaches out of the blue. The other 20%, however, experience sensations, usually visual, that warn them that a migraine is on the way. These symptoms are called an ‘aura.'
Typical experiences of visual auras include flickering or flashing lights and shapes that appear in your visual field and move or expand to cause partial loss of vision. These symptoms are most often on one side of the visual field—and it tends to be the side opposite the one on which the pain of migraine will be felt. Other experiences of migraine aura can include weakness or numbness on one side of the body or difficulty speaking (dysphagia).
Auras and migraines occur together in predictable ways. An aura typically lasts less than an hour—and may last just a few minutes. The pain of a migraine follows shortly, and, in most cases, the symptoms of an aura dissipate before or as the pain of migraine arrives. Auras that persist for longer than an hour are unusual and should be evaluated by a doctor.
Sometimes, visual disturbances occur without any pain at all, in a condition known as ocular or retinal migraines. These are thought to be due either to constriction or spasm of the artery within the brain that supplies the retinas with blood (in the case of auras that occur in both eyes) or in the retinal arteries themselves (in the case of auras on just one side of your visual field). Ocular or retinal migraines may last only 20 to 30 minutes, compared to the 4 to 72 hours that an untreated migraine will persist.
The proper diagnosis of auras—whether they occur in isolation as ocular migraines or with pain—is important. The symptoms of an ocular migraine can mimic those of other serious conditions, like retinal detachment (a flap of the delicate sensory tissue covering the rear of the eye tears lose from the supporting structure), retinal artery thrombosis (a clot in one of the vessels that supplies the retinas with blood), transient ischemic attacks (temporary loss of blood flow to areas of the brain from cardiovascular disease), or stroke (loss of blood flow to areas of the brain that persists long enough to cause permanent damage).
There is some evidence that the temporary visual disturbances of ocular migraines can become permanent. For this reason, they shouldn't be dismissed as less serious because they occur without pain. A helpful first step is a visit to the ophthalmologist, who can rule out any disorders of the delicate and irreplaceable retina at the back of the eye. A visit to a neurologist, especially a headache specialist if one is available, can help in getting a proper diagnosis and identifying appropriate treatments.
Ocular migraines should not be treated with triptans. Because the disturbance may be in the very small arteries that supply the retina, the constricting effect of triptans can decrease blood flow to the point where permanent retinal damage can occur.
The best treatment for ocular migraines is prevention: avoiding triggers, managing stress well, keeping a regular schedule, and getting a healthy amount of sleep. When auras occur both with and without migraines, some physicians may recommend a medication, like propranolol, as part of a prevention plan.