Abstract
BackgroundRetinal microvascular alterations have been previously described in Parkinson’s disease (PD) patients using optical coherence tomography angiography (OCT-A). However, an extensive description of retinal vascular morphological features, their association with PD-related clinical variables and their potential use as diagnostic biomarkers has not been explored.MethodsWe performed a cross-sectional study including 49 PD patients (87 eyes) and 40 controls (73 eyes). Retinal microvasculature was evaluated with Spectralis OCT-A and cognitive status with Montreal Cognitive Assessment. Unified PD Rating Scale and disease duration were recorded in patients. We extracted microvascular parameters from superficial and deep vascular plexuses of the macula, including the area and circularity of foveal avascular zone (FAZ), skeleton density, perfusion density, vessel perimeter index, vessel mean diameter, fractal dimension (FD) and lacunarity using Python and MATLAB. We compared the microvascular parameters between groups and explored their association with thickness of macular layers and clinical outcomes. Data were analyzed with General Estimating Equations (GEE) and adjusted for age, sex, and hypertension. Logistic regression GEE models were fitted to predict diagnosis of PD versus controls from microvascular, demographic, and clinical data. The discrimination ability of models was tested with receiver operating characteristic curves.ResultsFAZ area was significantly smaller in patients compared to controls in superficial and deep plexuses, whereas perfusion density, skeleton density, FD and lacunarity of capillaries were increased in the foveal zone of PD. In the parafovea, microvascular parameters of superficial plexus were associated with ganglion cell-inner plexiform layer thickness, but this was mainly driven by PD with mild cognitive impairment. No such associations were observed in controls. FAZ area was negatively associated with cognition in PD (non-adjusted models). Foveal lacunarity, combined with demographic and clinical confounding factors, yielded an outstanding diagnostic accuracy for discriminating PD patients from controls.ConclusionParkinson’s disease patients displayed foveal microvascular alterations causing an enlargement of the vascular bed surrounding FAZ. Parafoveal microvascular alterations were less pronounced but were related to inner retinal layer thinning. Retinal microvascular abnormalities helped discriminating PD from controls. All this supports OCT-A as a potential non-invasive biomarker to reveal vascular pathophysiology and improve diagnostic accuracy in PD.
Highlights
Parkinson’s disease (PD) is a progressive neurodegenerative disease characterized by motor impairment, including rest tremor, muscle rigidity, bradykinesia, and postural imbalance
The ganglion cell-inner plexiform complex (GCIPL) thinning is significantly more pronounced in PD patients over time compared to controls (Murueta-Goyena et al, 2021), but it is present from prodromal stages (Lee et al, 2019a,b), suggesting that an early but active neurodegeneration takes place in PD retina (Murueta-Goyena et al, 2021)
We aimed to extensively describe retinal vascular morphometric parameters in PD patients using high-resolution Spectralis optical coherence tomography (OCT)-A images, in order to verify the presence of microvascular abnormalities in PD compared to controls or specific alterations in PD-mild cognitive impairment (MCI) compared to PD patients with normal cognition
Summary
Parkinson’s disease (PD) is a progressive neurodegenerative disease characterized by motor impairment, including rest tremor, muscle rigidity, bradykinesia, and postural imbalance. The pathological features of PD have been observed in postmortem retinas (Ortuno-Lizaran et al, 2018), and several in vivo cross-sectional studies have reported reduced retinal thickness in PD by means of optical coherence tomography (OCT) (Chrysou et al, 2019). OCT angiography (OCTA) detects blood flow down to the capillary level by measuring changes in OCT signal in consecutive cross-sectional images taken at the same location and allows a three-dimensional mapping of retinal microvasculature. Studying the morphometric variations of capillary networks in PD might provide key information about the regional neuronal structure, and the basis for investigating retinal vascular morphological features as potential biomarkers of cerebral microcirculation in PD. Retinal microvascular alterations have been previously described in Parkinson’s disease (PD) patients using optical coherence tomography angiography (OCT-A). An extensive description of retinal vascular morphological features, their association with PD-related clinical variables and their potential use as diagnostic biomarkers has not been explored
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