Optical coherence tomography angiography (OCT-A) may serve as a noninvasive method to identify novel biomarkers for the early diagnosis of Parkinson disease, according to research results published in Ophthalmology Retina. The study found that a significant cohort of patients with the neurodegenerative condition had increased peripapillary microvascular density and flux. 

Researchers conducted a prospective, cross-sectional study (NCT03233646) to characterize the radial peripapillary capillary plexus in patients with and without Parkinson disease.

Two peripapillary OCT-A metrics were used: capillary perfusion density and capillary flux index. 


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The cohort included 151 eyes from 81 participants with Parkinson disease and 514 eyes from 314 control patients. Mean age was similar between groups (70.08±8.44 years vs 70.16±7.23 years in the Parkinson and control groups, respectively); however, the groups differed significantly in terms of sex distribution (38% and 72% women, respectively). Mean Hoehn and Yahr stage for patients with Parkinson disease were 2.12±0.62 with a majority of patients at stage 2 (43%). 

After adjusting for age and sex, peripapillary OCT-A imaging results showed significantly increased average, temporal, and nasal capillary perfusion densities in patients with Parkinson disease; superior and inferior capillary perfusion densities were also increased, but only approached—not exceeded—statistical significance. 

Average, temporal, superior, and nasal capillary flux indices were also significantly increased in the Parkinson population, with increases in inferior capillary flux index that were increased but not statistically significant. Between-group differences were “small but significant,” with an average β coefficient of 0.0083 and 0.0086 for capillary perfusion density and capillary flux index, respectively. 

Retinal nerve fiber layer (RNFL) thickness was also evaluated and was found to be similar between groups after adjustments were made for age and sex. The average RNFL thickness was similar between Parkinson disease and control groups (89.71±10.45 µm vs 88.20±10.33 µm), while superior RNFL thickness was significantly greater in the Parkinson group (109.79±15.70 µm vs 105.64±15.58 µm). 

Within the 71 patients in the Parkinson group who had both eyes imaged, results of a symmetry analysis showed that RNFL thickness, capillary perfusion density, and capillary flux index were similar between the patient’s eyes, excluding nasal RNFL thickness. 

The study’s limitations included an inability to confirm a histopathologic, postmortem Parkinson disease diagnosis in all participants and a lack of dilated ophthalmological examination. 

“These findings suggest that OCT-A imaging of the radial peripapillary capillary deserves to be further investigated as a potential biomarker for the diagnosis of Parkinson disease.” 

Reference

Robbins CB, Grewal DS, Thompson AC, et al. Identifying peripapillary radial capillary plexus alterations in Parkinson’s disease using optical coherence tomography angiography. Ophthalmol Retina. Published online March 10, 2021. doi:10.1016/j.oret.2021.03.006