Evaluation of retinal microvascular changes with OCT-A in Parkinson disease and essential tremor

This study aimed to evaluate the presence and comparison of microvascular abnormalities in essential tremor (ET) and Parkinson disease (PD) using optical coherence tomography angiography (OCT-A) and to show the relationship between retinal microvascular changes and disease stage in the patient group. A total of 176 eyes, including 26 PD diagnosed according to the United Kingdom PD Society Brain Bank criteria, 31 ET diagnosed according to the Washington heights-inwood genetic study of ET (WHIGET) criteria and 31 healthy controls, were included in the study. Unified PD assessment scale (UPDRS) motor scores, non-motor symptom scale (NMS), modified Hoehn&Yahr stages (mH&Y) and Fahn-Toloso-Marin grading scale were recorded. All patients were evaluated in terms of visual acuity, fundus examination, intraocular pressure measurements, and refractive errors in Ophthalmology department. Deep macular vascular density was significantly decreased in PD compared to both the controls and ET(P < .05). In the measurements in the inferior quadrant of the retinal nerve fiber layer (RNFL) of the optic disc (OD), the values of the controls were significantly higher than those of PD in both eyes (P = .014 and P = .010). Radial peripapillary capillarity density in the left eye was substantially lower in ET than in controls (P = .045). In both eyes, OD radial peripapillary capillarity inside the disc small values of PD were significantly lower than those of ET and controls (P < .05). In our study, deep macular vascular density, RNFL and radial peripapillary capillarity were significantly lower in PD compared with ET and control groups, and radial peripapillary capillarity was lower in ET compared with control group. This study provides valuable information regarding the potential of OCT-A as a diagnostic tool for PD and ET.