Characterization of Retinal Microvascular and Choroidal Structural Changes in Parkinson Disease

Question Can noninvasive retinal imaging parameters from optical coherence tomography angiography and enhanced depth imaging optical coherence tomography serve as novel biomarkers for the diagnosis of Parkinson disease (PD)? Findings In this cross-sectional study of eyes of 69 participants with PD and 137 healthy control participants, individuals with PD had decreased retinal vessel and perfusion densities, increased total choroidal area and choroid luminal area, and decreased choroidal vascularity index compared with age- and sex-matched control patients. Meaning Results of this study suggest that noninvasive retinal imaging parameters warrant further investigation as potential biomarkers in PD. This cross-sectional study compares the changes in optical coherence tomography parameters and choroidal structural parameters among adults with Parkinson disease and cognitively healthy individuals. Importance Noninvasive retinal imaging may detect structural changes associated with Parkinson disease (PD) and may represent a novel biomarker for disease detection. Objective To characterize alterations in the structure and microvasculature of the retina and choroid in eyes of individuals with PD and compare them with eyes of age- and sex-matched cognitively healthy control individuals using optical coherence tomography (OCT) and OCT angiography (OCTA). Design, Setting, and Participants This cross-sectional study was conducted at the Duke Neurological Disorders Clinic in Durham, North Carolina. Individuals aged 50 years or older with a diagnosis of PD were eligible for inclusion and underwent an evaluation and diagnosis confirmation before enrollment. Control individuals aged 50 years or older and without subjective cognitive dysfunction, a history of tremor, or evidence of motor dysfunction consistent with parkinsonism were solicited from the clinic or the Duke Alzheimer's Disease Prevention Registry. Individuals with diabetes, glaucoma, retinal pathology, other dementias, and corrected Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity worse than 20/40 Snellen were excluded. Data were analyzed between January 1, 2020, and March 30, 2020. Exposures All participants underwent OCT and OCTA imaging. Main Outcomes and Measures Generalized estimating equation analysis was used to characterize the association between imaging parameters and PD diagnosis. Superficial capillary plexus vessel density (VD) and perfusion density (PFD) were assessed within the ETDRS 6 x 6-mm circle, 6 x 6-mm inner ring, and 6 x 6-mm outer ring, as was the foveal avascular zone area. Peripapillary retinal nerve fiber layer thickness, macular ganglion cell-inner plexiform layer thickness, central subfield thickness, subfoveal choroidal thickness, total choroidal area, luminal area, and choroidal vascularity index (CVI) were measured. Results A total of 124 eyes of 69 participants with PD (39 men [56.5%]; mean [SD] age, 71.7 [7.0] years) and 248 eyes of 137 control participants (77 men [56.2%]; mean [SD] age, 70.9 [6.7] years) were analyzed. In the 6 x 6-mm ETDRS circle, VD (beta coefficient = 0.37; 95% CI, 0.04-0.71; P = .03) and PFD (beta coefficient = 0.009; 95% CI, 0.0003-0.018; P = .04) were lower in eyes of participants with PD. In the inner ring of the 6 x 6-mm ETDRS circle, VD (beta coefficient = 0.61; 95% CI, 0.20-1.02; P = .003) and PFD (beta coefficient = 0.015; 95% CI, 0.005-0.026; P = .004) were lower in eyes of participants with PD. Total choroidal area (beta coefficient = -1.74 pixels(2); 95% CI, -3.12 to -0.37 pixels(2); P = .01) and luminal area (beta coefficient = -1.02 pixels(2); 95% CI, -1.86 to -0.18 pixels(2); P = .02) were greater, but CVI was lower (beta coefficient = 0.5%; 95% CI, 0.2%-0.8%; P < .001) in eyes of individuals with PD. Conclusions and Relevance This study found that individuals with PD had decreased retinal VD and PFD as well as choroidal structural changes compared with age- and sex-matched control participants. Given the observed population differences in these noninvasive retinal biomarkers, further research into their clinical utility in PD is needed.