Optical coherence tomography (OCT) is a non-invasive retinal imaging technology that can provide high-resolution cross-sectional images of the peripapillary retinal nerve fiber layer (RNFL) and measure its thickness. A reduction of the RNFL thickness has been detected in several neurodegenerative diseases, such as multiple sclerosis, CADASIL and Alzheimer's disease. Different studies have reported RNFL changes also in migraine, is a common hereditary chronic neurovascular disorder, characterized by dysfunction of the autonomic nervous system. The pathophysiology of migraine has not been fully clarified, but there is increasing evidence that episodes of migraine with aura are initiated by a focal reduction in cerebral blood flow, which occurs most commonly in the posterior region of one hemisphere. Although vasoconstriction of cerebral and retinal blood vessels is a transient phenomenon, the chronic nature of the migraine might cause permanent structural abnormalities of the brain and also of the retina, which may correlate with RNFL thinning. Previous studies on this subject, however, reported contradicting results. Some investigations reported reductions of the RNFL thickness while others did not. In the present study, in order to determine whether RNFL thickness is reduced in migraine patients, the investigators performed a meta-analysis and systematically evaluated RNFL thickness measurements with OCT in a series of migraine patients and in the healthy control groups.