Functional and morphological changes of the retinal vessels in Alzheimer’s disease and mild cognitive impairment

Abstract

Imaging and histopathological studies have demonstrated that structural changes of the retina affect subjects with Alzheimer’s disease (AD) or mild cognitive impairment (MCI). The aim of this study was to quantitatively investigate the retinal vessels in these disorders, using dynamic vessel analyzer (DVA) and optical coherence tomography angiography (OCTA) analysis. Twelve subjects with AD, 12 subjects with MCI, and 32 gender- and age-matched controls were prospectively enrolled. Mean ± SD age was 72.9 ± 7.2 years in the AD group, 76.3 ± 6.9 years in the MCI group, and 71.6 ± 5.9 years in the control group (p = 0.104). In the DVA dynamic analysis, the arterial dilation was decreased in the AD group (0.77 ± 2.06%), in the comparison with the control group (3.53 ± 1.25%, p = 0.002). The reaction amplitude was decreased both in AD (0.21 ± 1.80%, <0.0001) and MCI (2.29 ± 1.81%, p = 0.048) subjects, compared with controls (3.86 ± 1.94%). OCTA variables did not differ among groups. In the Pearson correlation analysis, amyloid β level in the cerebrospinal fluid was directly correlated with the arterial dilation (R = 0.441, p = 0.040) and reaction amplitude (R = 0.580, p = 0.005). This study demonstrate that Alzheimer’s and MCI subjects are characterized by a significant impairment of the retinal neurovascular coupling. This impairment is inversely correlated with the level of amyloid β in the cerebrospinal fluid.

Neurofilament light chain in the vitreous humor of the eye

“…For example, the retinal nerve fiber layer (RNFL) is thinner, the retinal volume is reduced, and the choroidal thickness is reduced in patients with mild cognitive impairment (MCI) and AD compared to cognitively normal (CN) controls [25][26][27][28][29][30][31][32][33][34][35][36][37][38]. A newer and more sophisticated version of the OCT, the optical coherence tomography angiography (OCTA), has shown significant changes to the superficial and deep capillary vascular plexus of the macula and changes to the foveal avascular zone in those with cognitive dysfunction and AD compared to CN controls [39][40][41][42][43][44][45][46][47][48][49]. However, data obtained by OCT/OCTA, while promising, have shown conflicting results and can be confounded by the presence of co-existing eye disease and systemic diseases, such as diabetes, as well as variations in cell layer measurements by different automated platforms [50].…”

Anatomical and functional changes in the retina in patients with Alzheimer’s disease and mild cognitive impairment

“…Kotliar and colleagues reported increased flicker response in retinal veins of patients with AD and MCI, a finding that was interpreted by the authors as either neuronal activity being increased or the feedback loop of neurovascular coupling being damaged (Kotliar et al 2017). However, the data from Kotliar et al are in disagreement with more recently published data: Using the same instruments for the measurement of flicker-induced vasodilatation, Querques et al report that patients with MCI have reduced flicker responses compared to healthy subjects (Querques et al 2019). The reason for this difference has yet to be clarified, but may be related to differences in the patients' characteristics between the studies.…”

OCTA in neurodegenerative optic neuropathies: emerging biomarkers at the eye–brain interface

“…This is especially important since MCI is a complex, heterogeneous group that includes patients who may not progress to AD, may revert back to being cognitively normal, or may demonstrate non-AD dementia. 40 Querques and colleagues 41 evaluated the functional and morphological characteristics of the retinal vasculature in AD and MCI. Using both dynamic vessel analyzer (DVA) and OCTA, the study demonstrated significant impairment of retinal neurovascular coupling not only in AD, but also in MCI.…”