The Role Of OCT/OCTA Ocular Biomarkers On Diagnosing Parkinson Disease

The Role Of OCT/OCTA Ocular Biomarkers On Diagnosing Parkinson Disease

October 17, 2021

In the management of Parkinson's disease, reliable diagnostic and prognostic biomarkers are urgently needed.

The diagnosis of Parkinson's disease mostly relies on clinical symptoms, which hampers the detection of the earliest phases of the disease—the time at which treatment with forthcoming disease-modifying drugs could have the greatest therapeutic effect.

There is no single diagnostic test for Parkinson disease (PD), and neurologists often rely on the patient’s response to medications to differentiate the disease from conditions with similar symptoms.

Sensitive and specific biomarkers for Parkinson’s disease (PD) presence and severity have been largely elusive. OCT changes have been shown in PD; however, few studies have explored retinal microvascular changes.

Neuroimaging combined with OCTA has the potential to uncover correlates of disease and identify early biomarkers to facilitate disease-modifying drug discovery.

Investigators at Duke University have taken a step toward establishing an adjunctive approach using retinal imaging to diagnose PD.

They used enhanced-depth optical coherence tomography (OCT) as well as OCT angiography (OCTA), both noninvasive technologies, to evaluate patients who had received a clinical diagnosis of PD in order to identify ocular structural differences between patients with PD and healthy controls.

Cason B. Robbins, BS, of the Department of Ophthalmology at Duke University School of Medicine in Durham, North Carolina, lead author of the study, evaluated the retinal microvascular and choroidal structural changes in the eyes of patients with PD.

Previous study results indicated that cerebral small vessel disease may be a potential risk factor for development of PD, and PD has a higher prevalence of cerebral ischemic lesions, Robbins et al noted.

The study and results Participants were enrolled at the Duke Neurological Disorders Clinic. The 69 patients (124 eyes; mean age, 71.7 years) had received an established clinical diagnosis of PD. There were 137 cognitively healthy controls (248 eyes; mean age, 70.9 years).

All patients underwent OCT and OCTA. The investigators assessed the superficial capillary plexus vessel density (VD) and perfusion density (PFD) within the Early Treatment Diabetic Retinopathy Study (ETDRS) 6 × 6-mm circle, 6 × 6-mm inner ring, 6 × 6-mm outer ring, and the foveal avascular zone.

The investigators measured the 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).

                                                                                 

The results showed that compared with the healthy sex- and age-matched controls, the VD and PFD were significantly lower in the patients with PD in the 6 × 6-mm ETDRS circle (P = 0.3 and P = 0.4, respectively) and in the 6 × 6-mm inner ring (P = .003 and P = .004, respectively).

The total choroidal area and luminal area were larger in the patients with PD (P = 0.1 and P = 0.2, respectively). The CVI was lower in the patients with PD.

The results did not show differences in the retinal nerve fi ber layer or ganglion cell layer thickness or the subfoveal choroidal thickness, the latter of which diff ers from the results of some other studies.

Robbins joined Sharon Fekrat, MD, a professor of ophthalmology at Duke University School of Medicine; Dilraj S. Grewal, MD, an associate professor of ophthalmology at Duke University School of Medicine; and the other coauthors in pointing out that the current findings are combined with the clinical history and other tests.

“These choroidal and retinal microvascular imaging findings may hold the potential to improve clinician confidence in the diagnosis of PD,” they wrote.

According to the investigators, the findings highlight the need for further research into retinal imaging as a potential novel biomarker for individuals with neurodegenerative diseases such as PD.

“Future long-term studies that characterize the natural history of microvascular and structural retinal changes in individuals across the clinical spectrum of PD [are] warranted,” they concluded. “Studies may help clarify whether these imaging findings may be useful as biomarkers for the onset of PD.

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