Objective: To detect changes in retinal thickness and their possible correlates with microvascular pattern in early PD patients as compared to controls.

Background: Physiologically, retinal dopaminergic neurons modulates colour vision and contrast sensitivity. Retinal dopaminergic depletion has been observed in Parkinson’s Disease (PD), possibly explaining some of the associated visual symptoms. Spectral-domain optical coherence tomography (SD-OCT) studies demonstrated thickness reduction of the inner retinal layer in PD patients, notably in the nerve fiber layer (RNFL) [1]. However, few studies have focused on possible correlation between RNLF thickness and retinal microvascular angiographic pattern [2].

Method: Patients fulfilling UK-Brain-Bank criteria for PD were recruited. Healthy subjects were also  enrolled as controls. Exclusion criteria were glaucoma, concurrent retinal disease, ocular trauma, cataract, high intraocular pression, systemic disease impairing visual system (diabetes, uncontrolled hypertension/hypotension, cardiovascular diseases) and other neurological diseases. Retinal microvascular pattern was analysed using coherence tomography angiography (OCT-A) and segmentation analysis of retinal layers using SD-OCT. Retinal microvasculature was automatically divided into superficial and deep capillary plexus (SCP and DCP) to be analyzed.

Results: N=21 eyes from PD patients (age: 63.33±6.78 years) and N=16 eyes from healthy controls (age: 57.25±6.87 years) were evaluated. Considering age difference between-group, statistical inference has been performed using age as covariate. PD patients showed significant lower microvascular density in each macular DCP zones, compared to controls. Thickness of RNFL resulted significantly lower in PD patients as compared to control (p=0.05). In PD patients, there was a positive correlation between RNFL thickness and both superficial and deep foveal microvascular density (respectively, r=0.67, p=0.006; r=0.65, p=0.008).

Conclusion: Retinal microvascular impairment and thinner RNFL were found in PD patients with respect to controls. The correlation we found between foveal microvascular density and intraretinal layers thickness in our PD study patients could partially explaine visual symptoms described since the early stage of disease.

References: 1. Maria Satue, JavierObis, Maria J. Rodrigo, Sofia Otin, MariaI Fuertes, Elisa Vilades, Hector Gracia, Jose R. Ara, Raquel Alarcia, Vicente Polo, Jose M. Larrosa, Luis E. Pablo and Elena Garcia-Martin. Optical Coherence Tomography as a Biomarker for Diagnosis, Progression, and Prognosis of Neurodegenerative Diseases. 2016. J Ophthalmol. 2016; 2016: 8503859. 2. William Robert Kwapong, Hua Ye, Chenlei Peng, Xiran Zhuang, Jianhua Wang, Meixiao Shen, and Fan Lu. Retinal Microvascular Impairment in the Early Stages of Parkinson’s Disease. Invest Ophthalmol Vis Sci. 2018 Aug 1;59(10):4115-4122.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/retinal-thickness-and-microvascular-pattern-in-early-parkinsons-disease/