Visual System Dysfunction in Migraine

Abstract

This paper reviews both clinical and experimental literature relating to visual dysfunction in migraine, starting with the eye and progressing via the retina and visual pathways to the visual cortex. Migraine is associated with (i) a pupillary sympathetic hypofunction, and (ii) a cortical hypersensitivity to visual stimuli (perhaps only in migraine with aura), the pathogenesis of which remains to be determined. Various hypotheses are discussed, and it is proposed that the methods of visual psychophysics may represent a useful approach in the future study of cortical hyperexcitability in migraine. Paradoxically, little research has been directed towards understanding (i) the photophobia of migraine attacks, and (ii) how migraine may be triggered by visual stimuli. Research aimed at elucidating the mechanisms of these phenomena may enhance understanding of the pathogenes is of migraine. The clinical and psychophysical findings reviewed above reveal a broad agreement that migraine is associated with (i) a pupillary sympathetic hypofunction, and (ii) a cortical hypersensitivity to visual stimuli (perhaps only in migraine with aura). Evidence for other dysfunctionality in the eye, retina or visual pathways is, in our view, equivocal. In spite of the research effort thus far, visual phenomena which are integral to migraine symptomatology are very poorly understood. We would contend that research aimed at understanding the neurological basis of the visual triggering of migraine and of photophobia would assist a more complete understanding of the disorder, and perhaps shed light on processes occurring at the very initiation of an attack. We suggest also that further investigations into the nature and cause of the dysfunction of the visual cortex in migraine with aura may assist the development of general pathophysiological theories.