Parkinson Disease: Noninvasive Retinal Imaging Parameters May Be Potential Biomarkers

Individuals with Parkinson disease (PD) appear to have decreased retinal vessel and perfusion densities and choroidal vascularity index, as well as increased total choroidal area and choroid luminal area, according to a new cross-sectional study (N = 206) published in JAMA Ophthalmology.

According to the authors of the study, “noninvasive retinal imaging parameters warrant further investigation as potential biomarkers in PD.”

Neurology Learning Network discussed these findings and their implications further with study authors Dilraj S. Grewal, MD and Sharon Fekrat, MD, ophthalmologists and retinal surgeons at Duke University School of Medicine in Durham, North Carolina, and Cason Robbins, medical student at Duke University School of Medicine in Durham.

NLN: In your study, you and your colleagues found that noninvasive retinal imaging parameters should be investigated further as potential biomarkers of PD. Could you discuss this in more detail?

Dr Grewal: Using retinal imaging, optical coherence tomography (OCT) and OCT angiography (OCTA), our iMIND research group found retinal microvasculature alterations among individuals with PD with decreased vessel density and perfusion density compared with age- and sex-matched controls. 

We also found structural alterations in the choroid in eyes of participants with PD, which were not observed in controls, with a decreased choroidal vascularity index. Both groups were similar in terms of central subfield thickness in the retina, as well as ganglion cell layer and retinal nerve fiber layer thickness. 

NLN: If these findings are replicated in future work, how might they impact clinical practice and/or screening for PD?

Dr Fekrat: The ultimate goal is to be able to use these retinal and choroidal markers as noninvasive adjuncts to a clinical examination and neuroimaging to be able to diagnose PD and potentially do so early in the disease process. This would allow future potential interventions to be evaluated earlier in the disease process, and they might be more effective in earlier stages. There are obvious advantages of this approach for screening with the test being rapid, noninvasive, low-cost, easy to use, and reproducible.

NLN: Could you discuss the areas of future research that are still needed in this field?

Dr Grewal: The main issue that needs to be addressed is the specificity of these findings. The retinal microvascular changes we observed are also seen in diseases such as diabetes, glaucoma, and hypertension, which are more common among older adults. In our study, we excluded participants with such comorbidities, but in order to develop a retinal biomarker that can be broadly applied, we need to determine how the pattern of retinal changes in PD is different from these comorbidities. This work opens up multiple areas for future research, including the use of deep learning to assist in this task.

NLN: What key takeaways about this topic do you hope to leave with neurologists, ophthalmologists, and related providers?

Dr Fekrat: There are retinal and choroidal changes in PD and, with further research, we might be able to develop these into clinically useful biomarkers to assist in early diagnosis.

—Christina Vogt

Reference:
Robbins CB, Thompson AC, Bhullar PK, et al. Characterization of retinal microvascular and choroidal structural changes in Parkinson disease. JAMA Ophthalmol. Published online December 23, 2020. doi:10.1001/jamaophthalmol.2020.5730