Researchers are exploring a number of vasogenic stimulus theories for the pathogenesis of migraine headache and, with the choroid being the most vascularized tissue of the eye, it has become the center of interest, according to a report published in Photodiagnosis and Photodynamic Therapy. Investigators include in these reviews spasms of cerebral and retrobulbar blood vessels.  

The research suggests chronically reduced blood flow may be a risk factor for damage to the retina and optic nerve. 

The prospective cross-sectional study explores choroidal vascularity index, peripapillary RNFL thickness, and optic density index (ODI). A number of prior analyses have revealed decreased mean retinal nerve fiber layer (RNFL) thickness, or thickness reductions in particular quadrants of patients with migraine. The new investigation is first to use enhanced depth imaging optical coherence tomography (EDI-OCT) and binarized choroidal structural parameters to evaluate ocular structures of 56 participants; 28 diagnosed less than 3 months prior with migraine (without aura), and 28 healthy individuals. 


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The mean choroidal area (CA) for those with recurrent migraines was 0.834±0.108 mm, compared with 0.986±0.248 mm in healthy participants (P =.012); and luminal area (LA) in case patients was 0.579±0.112 mm, in contrast to control individuals with 0.725 ±0.191 mm (P =.003). In calculating choroidal vascularity index as the proportion of LA to total CA, mean choroidal vascularity index was 69.43% for those with migraine, and 73.38% in healthy volunteers (P =.035), a significant difference.

Patients with migraine also displayed significant differences in overall mean RNFL thickness; 102.23±9.09 μm, compared with 107.19±6.93 μm in individuals in the control group (P =.040). The mean superior RNFL quadrant thickness in case patients was thinner than in control participants (P =.030), as well as the inferior region (P =.022). This difference persisted in the temporal quadrant (P =.001), but thinning was not significant nasally (P =.082). No significant differences were found between groups for mean ODI of RNFL; 0.934±0.064 in those with migraine, and 0.949±0.057 in healthy volunteers (P =.399). 

This investigation took place at Ahi Evran University, in Kırşehir, Turkey, from January 2021 to May 2021. Participants’ mean age was similar between cohorts; 38.4 years in the case group and 38.9 in the control set. Sex was also comparable, with 15 women, 13 men among those with migraine; and 14 women, 14 males as control individuals.

Limitations of this analysis include a somewhat small sample, and no follow-up to measure long-term changes. Also, choroidal vascularity index does not measure blood flow velocity. Strengths encompass the variety of measurements employed, including ODI. Previous studies using SD-OCT and OCT angiography have demonstrated a significant difference in mean choroidal thickness for patients with migraine compared with healthy controls, or have found that migraine was associated with foveal vascular reduction, or vessel density.

“Evaluating the vascular parameters with the help of the binarization method gives further information about the vascular and stromal components of the choroid,” the study explains. It adds that choroidal vascularity index is not greatly impacted by physiologic factors and has been accepted as a biomarker for several ocular disorders.

Reference

Temel E, Aşikgarıp N, Koçak Y, Choroidal vascularity index and retinal nerve fiber layer reflectivity in newly diagnosed migraine patients. Photodiagnosis and Photody Ther. Published online September 11, 2021, doi:10.1016/j.pdpdt.2021.102531