Retinal microvascular impairment in Parkinson's disease with cognitive dysfunction

Parkinson's disease (PD) is associated with structural alterations of the retina. However, it remains unknown whether these changes are present in PD with mild cognitive impairment (MCI). The purpose of the study was to evaluate the retinal microvasculature using optical coherence tomography angiography (OCTA) to assess possible retinal microvascular impairments associated with PD and PD with MCI.This study included 83 eyes of 45 PD patients and 83 eyes of 42 healthy controls. All subjects underwent complete neurological and ophthalmological examinations before measurements. Cognitive function was also measured in PD patients. Retinal microvasculature was evaluated with OCTA. Vessel density in the superficial capillary plexus (SRCP), deep capillary plexus (DRCP), and radial peripapillary capillaries (RPC) and intraretinal layer thickness in the peripapillary retinal nerve fibre layer (RNFL) and ganglion cell complex (GCC) were analysed. Correlations between vessel density and cognitive function were analysed in the PD group.Parafoveal vessel density in the SRCP and DRCP were lower in the eyes of PD patients than healthy controls (P < 0.05). However, there were no significant differences in the RPC (P = 0.120), RNFL (P = 0.303) or GCC (P = 0.375) between PD patients and healthy controls. Lower executive function scores were associated with lower vessel density in the DRCP of PD patients (P < 0.05, 95% CI [0.133,1.342]).OCTA revealed lower macular microvascular density in PD patients and microvascular impairments in the deep retinal capillary layer in PD patients with executive dysfunction. These parameters might have potential utility as early disease diagnostic biomarkers.