Retinal and Choroidal Microvascular Changes Across the Migraine Attack Cycle: A Systematic Review and Exploratory Quantitative Synthesis

Migraine is an episodic neurovascular disorder, but whether ocular microvascular abnormalities detected by optical coherence tomography angiography (OCTA) vary across the attack cycle or represent persistent interictal characteristics remains uncertain. This systematic review evaluated phase-anchored retinal, optic nerve head, and choroidal OCTA findings and assessed the consistency of available quantitative evidence. PubMed, Scopus, Web of Science, and Google Scholar were searched from inception through June 25, 2026, for original human studies reporting OCTA measurements during ictal, interictal, or clearly defined attack-free periods. Seven observational studies met the eligibility criteria, of which 3 (43%) provided paired ictal-interictal measurements; additional studies contributed ictal-versus-healthy-control and interictal-versus-control evidence, with some studies contributing to more than one comparison family. The strongest attack-related signal involved reduced parafoveal perfusion, including an approximately 7% decrease in vessel flux index during attacks in both migraine-with-aura and migraine-without-aura groups, together with a reduction in foveal choriocapillaris vessel density from 64.91% interictally to 63.34% ictally. Interictal-control studies also identified lower central superficial and deep capillary plexus vessel density and larger foveal avascular zone measurements in selected cohorts, whereas retinal and peripapillary findings overall were less consistent. After accounting for shared controls, same-study subgroups, paired measurements, bilateral-eye dependence, anatomical region, vascular layer, outcome metric, and measurement unit, no outcome stratum contained at least two independent statistically compatible studies suitable for formal pooling. Methodological concerns centered mainly on statistical analysis, bilateral-eye handling, confounding, and incomplete reporting, and certainty of evidence was very low. Overall, the findings support phase- and compartment-specific ocular microvascular changes in migraine, with the clearest dynamic abnormalities involving the parafoveal and choriocapillaris circulation. However, the current evidence remains insufficient to establish OCTA as a reproducible clinical or diagnostic biomarker.