Eccentricity Dependency of Retinal Electrophysiological Deficits in People With Episodic Migraine

Abstract

Purpose: During the non-attack period, people with migraine may show retinal dysfunction. This study builds on previous work by exploring the possibility of foveal and non-foveal visual field and electroretinographic deficits and determining the overlap in eccentricity of such localized visual deficits in people with migraine.

Methods: Visual fields and multifocal electroretinography (mf-ERG) were tested in 27 people with migraine (aged 19-45 years) and 18 non-headache controls (aged 20-46 years). Data were averaged according to 5 concentric rings at < 1.5 degrees (foveal) and 5 degrees, 10 degrees, 15.5 degrees, and 22 degrees eccentricities (non-foveal). Linear mixed effects modelling was used to predict mf-ERG amplitude, mf-ERG peak time, and visual field sensitivity with fixed effects of eye, group, and eccentricity.

Results: Foveal mf-ERG responses, and visual field sensitivity across all eccentricities (foveal and non-foveal) were similar between the migraine and control groups (P > 0.05). In contrast, the non-foveal mf-ERG was reduced in amplitude in people with migraine relative to controls (P < 0.001), and this group difference depended on eccentricity (P < 0.001) - most prominently, in the parafoveal region (ring 2, P = 0.001).

Conclusions: Retinal electrophysiological deficits were observed in people with migraine in the parafoveal region (between 1.5 degrees and 5 degrees eccentricity), without corresponding visual field deficits. This suggests a spatially localized area of retinal neuronal dysfunction in people with migraine that is insufficient to manifest as a visual field sensitivity loss using standard perimetric methods. Our study highlights the added confound of migraine when conducting standard clinical retinal electrophysiological tests for conditions such as glaucoma, particularly non-foveally.

Figure 1.

Schematic of mf-ERG methodology. (A) The stimulus array fell within the central 44 degrees diameter (up to 22 degrees eccentricity). (B) Hexagons were arranged in five rings, scaled for eccentricity, and responses were averaged within each ring for analysis. (C) Averaged waveforms for each ring were analyzed for peak-to-peak amplitude and peak time relative to total ring area.

Figure 2.

Ringwise mf-ERG peak amplitude for the non-headache control (unfilled) and migraine (filled) groups at (A) ring 1 at < 1.5 degrees eccentricity, (B) ring 2 at 1.5 degrees to 5 degrees eccentricity, (C) ring 3 at 5 degrees to 10 degrees eccentricity, (D) ring 4 at 10 degrees to 15.5 degrees eccentricity, and (E) ring 5 at 15.5 degrees to 22 degrees eccentricity. Individual data are shown with the group mean ± 95% confidence intervals of the mean.

Figure 3.

Ringwise mf-ERG peak times for the non-headache control (unfilled) and migraine (filled) groups at (A) ring 1 at < 1.5 degrees eccentricity, (B) ring 2 at 1.5 degrees to 5 degrees eccentricity, (C) ring 3 at 5 degrees to 10 degrees eccentricity, (D) ring 4 at 10 degrees to 15.5 degrees eccentricity, and (E) ring 5 at 15.5 degrees to 22 degrees eccentricity. Individual data are shown with the group mean ± 95% confidence intervals of the mean.

Figure 4.

Ringwise visual field sensitivity for the non-headache control (unfilled) and migraine (filled) groups at (A) ring 1 at < 1.5 degrees eccentricity, (B) ring 2 at 1.5 degrees to 5 degrees eccentricity, (C) ring 3 at 5 degrees to 10 degrees eccentricity, (D) ring 4 at 10 degrees to 15.5 degrees eccentricity, and (E) ring 5 at 15.5 degrees to 22 degrees eccentricity. Individual data are shown with the group mean ± 95% confidence intervals of the mean.