Objective: The study aims to explore differences in retinal thickness between GBA1-related Parkinson Disease (GBA1-PD) and non-mutated PD (NM-PD) and to analyze correlations between clinical and retinal parameters.

Background: Parkinson’s Disease (PD) patients exhibit retinal thinning compared to healthy controls according to previous studies [1], [2]. Moreover, these changes seem to correlate with disease severity and cognitive impairment although data in literature are still debated [2], [3]. Currently, there are no data about retinal structural changes in GBA1-PD patients.

Method: A consecutive cohort of GBA1-PD patients was matched with a cohort of NM-PD patients according to age, sex, disease duration, H&Y stage. Clinical assessment, including MDS-UPDRS and MoCA, was performed in the whole cohort. Moreover, all patients underwent optical coherence tomography (OCT) to evaluate retinal nerve fiber layer (RNFL) thickness with three circular scans (diameters: 3.5-,4.1- and 4.7-mm).

Results: The study included 52 PD patients (104 eyes from 26 GBA1-PD and 26 NM-PD). Clinical variables did not show statistically significant differences between GBA1-PD and NM-PD. Temporal RNFL thickness was significantly reduced in NM-PD compared to GBA1-PD at 3.5-, 4.1- and 4.7 mm (p=0.021, p=0.006, p=0.005 respectively). In the total PD cohort, the average temporal RNFL thickness (4.1 mm scan) showed an inverse correlation with MDS-UPDRS part I total score (p=0.04).

Conclusion: Our results show a reduced retinal thickness in NM-PD compared to GBA1-PD, highlighting a higher involvement of papillo-macular bundle in NM-PD than in GBA1-PD. This may reflect different retinal cells’ involvement, potentially related to distinct pathophysiological mechanisms. Interestingly, in the total PD cohort, as main result, temporal RNFL was found to be inversely correlated with the burden of non-motor symptoms.

This abstract was previously presented at the 11th European Academy of Neurology (EAN) Congress, Helsinki (Finland), 21-24 June 2025.

References: [1] Yu JG, Feng YF, Xiang Y, Huang JH, Savini G, Parisi V, Yang WJ, Fu XA. Retinal nerve fiber layer thickness changes in Parkinson disease: a meta-analysis. PLoS One. 2014 Jan 21;9(1):e85718.
[2] Ahn J, Lee JY, Kim TW, Yoon EJ, Oh S, Kim YK, Kim JM, Woo SJ, Kim KW, Jeon B. Retinal thinning associates with nigral dopaminergic loss in de novo Parkinson disease. Neurology. 2018 Sep 11;91(11):e1003-e1012.
[3] Chang Z, Xie F, Li H, Yuan F, Zeng L, Shi L, Zhu S, Lu X, Wei X, Wang Q. Retinal Nerve Fiber Layer Thickness and Associations With Cognitive Impairment in Parkinson’s Disease. Front Aging Neurosci. 2022 Feb 10;14:832768.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/retinal-structural-changes-in-parkinsons-disease-insight-into-gba1-related-pd-and-non-mutated-pd/