Objective: This observational cross-sectional study aims to explore the thickness of retinal layers in patients within the PD continuum, patients with isolated REM Sleep Behavior Disorder (iRBD), and healthy controls (HC). The objective was to assess the thickness of the retinal peripapillary nerve fiber layer (pRNFL) across various retinal quadrants, as well as in other retinal layers such as the ganglion cell layer (GCL) and inner plexiform layer (IPL).

Background: The retina is considered “a window to the CNS,” as it is an easily examinable district of the CNS, using techniques like optical coherence tomography (OCT). Previous OCT studies in patients with neurodegenerative disorders, such as PD and iRBD, have revealed thinning of the macular ganglion cell and inner plexiform layers (GCL-IPL) of the neuroretina and the RNFL compared to healthy controls.

Method: This observational cross-sectional study included 15 HC subjects, 25 iRBD patients diagnosed through polysomnography, and 11 PD patients diagnosed by expert neurologists specialized in movement disorders. Patients with retinal diseases (maculopathy, retinopathy, etc.) and patients with glaucoma or increased intraocular pressure, were excluded. Retinal layers were studied using OCT. Statistical analysis was performed using SPSS software.

Results: Statistical analysis of preliminary data revealed significant thinning of the pRNFL in the upper and nasal quadrants in iRBD patients compared to HC subjects. In PD patients, a significant reduction in pRNFL thickness in the temporal quadrant was observed compared to HC subjects. Although thinning was also observed in other macular retinal layers (GCL, IPL, and total retinal thickness), the statistical analysis did not show significant values.

The preliminary data of this study also represent the baseline (time 0) of a prospective study; for this reason, future recruitment of additional patients and follow-up evaluations are planned to further validate and refine these results. The ongoing expansion of the cohort will help assess whether the observed retinal changes correlate with disease progression.

Conclusion: Although preliminary, our data suggest that retinal changes could serve as indicators of neurodegeneration along the PD continuum (alpha-synucleinopathy), even in the early and prodromal stages, as evaluated in patients with iRBD, which is considered the strongest marker for the diagnosis of “prodromal PD”.

References: [1] Considering REM Sleep Behavior Disorder in the Management of Parkinson’s Disease. Figorilli et al. 2023
[2] Retinal thickness and microvascular pathway in Idiopathic Rapid eye movement sleep behaviour disorder and Parkinson’s disease. Rascunà et al. 2021
[3] Retinal Optical Coherence Tomography Features Associated With Incident and Prevalent Parkinson Disease. Wagner et al. 2023
[4] Structural and functional changes in the retina in Parkinson’s disease. Alves et al. 2023

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-novel-potential-imaging-biomarker-for-parkinsons-disease-optical-coherence-tomography/