The IHS code is 1.4 for retinal migraine. A short description from the Headache Classification Committee is the following: repeated attacks of monocular scotoma or blindness lasting less than one hour and associated with headache. Other ocular or structural vascular disorder must be ruled out. Additional terms include: ocular migraine, anterior visual pathway migraine, and ophthalmic migraine. This condition may be broadly defined as a transient or permanent monocular visual disturbance accompanying a migraine attack or occurring in an individual with a strong history of migrainous episodes. Retinal migraine occurs more frequently than ophthalmoplegic migraine. We estimate the frequency of strictly monocular visual phenomena occurring in conjunction with migraine to be one of 200 migraine sufferers. Frequently, however, homonymous visual field phenomena in migraineurs is incorrectly attributed to a single eye. For example, a patient with transient right homonymous hemianopia might think that the right eye is affected, because normally the right temporal hemifield is 30-40 degrees larger than the left nasal hemifield.