Objective: To evaluate the association between retinal structural changes, as measured by optical coherence tomography (OCT), and non-motor symptoms severity in patients with Parkinson’s disease (PwP).

Background: The retina can be used as a model to examine neuronal and microvascular damage in the brain, as it originates from the prosencephalon during embryogenesis. Dopaminergic cells with D1 and D2 receptors have been found in the inner nuclear layer (INL) and inner plexiform layer (IPL) of the retina. These receptors play a key role in organizing the receptive field of retinal ganglion cells (GCL). Retinal structural changes have been observed with OCT, revealing thinning of the nerve fiber layer (NFL). OCT is a non-invasive biomarker of neurodegeneration, its correlation with the severity of non-motor symptoms could be promising.

Method: An observational, cross-sectional case-control study was conducted with patients from the National Institute of Neurology and Neurosurgery in Mexico. Non-motor symptom severity was assessed using the MDS-NMS scale, and OCT was performed on both eyes to measure the thickness and volume of the foveal, parafoveal, and perifoveal regions of the INL, IPL, GCL, and NFL. Descriptive statistics, mean comparisons, and correlation analyses were performed.

Results: A total of 17 PwP (34 eyes) and 51 controls (102 eyes) in a 1:3 ratio were included, with a mean age of 63 ± 7.8 years, and 52.9% were men. The mean disease duration was 9.5 years. Compared to controls, patients with PD exhibited lower volumes in multiple retinal layers, including the parafoveal IPL (p = 0.039), perifoveal IPL (p = 0.004), perifoveal INL (p = 0.003), perifoveal NFL (p = 0.005), and parafoveal GCL (p = 0.036). A multivariate analysis with variables showing correlation with greater non-motor symptoms severity, along with disease duration, age, and LEDD, showed that the only significant result was the parafoveal GCL volume (r=0.56, p<0.001), positively correlated with greater gastrointestinal symptoms severity.

Conclusion: As previously published, retinal layer thinning was observed in patients compared to controls. Additionally, a positive correlation between gastrointestinal symptoms and greater parafoveal GCL volume was observed, a finding not previously reported. Larger studies are needed to confirm these findings

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MDS Abstracts - https://www.mdsabstracts.org/abstract/structural-changes-in-the-retina-and-their-correlation-with-the-severity-of-non-motor-symptoms-in-patients-with-parkinsons-disease/