Retinal Vascularity Index in Parkinson's Disease

To assess differences in retinal vascularity index (RVI) between individuals with Parkinson's disease (PD) and controls to explore RVI as a potential retinal biomarker of PD.

Cross-sectional case-control study.

One hundred sixty-eight eyes of 108 PD participants and 115 eyes of 71 control participants in the Eye Multimodal Imaging in Neurodegenerative Disease Study.

Ultra-widefield (UWF) retinal color photographs were acquired in each participant using scanning laser ophthalmoscopy (California, Optos). Images were analyzed using a semiautomated software via the Comprehensive Ocular Imaging Network (ocularimaging.net). Retinal vascularity index was calculated as the ratio of arteriolar to venular cross-sectional area within a 47° region of interest (ROI) centered on the optic disc.

Five RVI outcomes in the 47° ROI were compared between groups: total, superonasal, superotemporal, inferotemporal, and inferonasal (IN).

Mean total RVI was significantly higher in the PD group (0.790 ± 0.134) than in controls (0.696 ± 0.117, P < 0.001). Retinal vascularity index in each quadrant was also significantly higher in PD than in controls: superonasal (P < 0.001), superotemporal (P = 0.005), inferotemporal (P < 0.001), and IN (P < 0.001).

Retinal vascularity index was significantly higher in individuals with PD than in controls. These findings may reflect alterations in retinal vascular structure in PD. Discriminatory analyses suggest that RVI is currently unlikely to stand alone as a diagnostic tool. Further investigation is warranted to determine whether RVI derived from a 5-disc diameter area on UWF images may serve as a potential retinal biomarker of PD.

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