Retinal blood flow and neurovascular coupling in patients with Alzheimer’s disease and mild cognitive impairment

Abstract

Purpose : There is evidence that neurodegenerative diseases such as Alzheimer’s disease (AD) or mild cognitive impairment (MCI) are associated with alterations in the retina. The aim of the present cross-sectional study was to assess retinal structural and functional parameters in patients with AD/MCI and healthy age- and sex matched controls.

Methods : Forty-seven patients with AD/MCI (mean age: 73 ± 9 years) and 43 healthy control subjects (mean age: 71 ± 7 years) were included. Patients with AD had to have a confirmed diagnosis of AD of mild to moderate degree and a Mini Mental State Examination (MMSE) score between 20 and 26 points. MCI was defined as documented abnormal memory function and MMSE score > 26 points. All included patients and control subjects had no ocular diseases. Retinal blood flow was measured using a custom-built Doppler optical coherence tomography (OCT) system. Retinal vessel diameters and flicker induced vasodilatation was measured using a Retinal Vessel Analyzer (RVA, Imedos, Germany). Retinal nerve fiber layer thickness (RNFLT) was assessed using an OCT system (Heidelberg Spectralis OCT, Heidelberg Engineering, Germany).

Results : Global RNFLT was lower in patients with AD/MCI compared to healthy controls (93.7 ± 12.8 µm vs. 99.1 ± 9.0µm, p = 0.02). The same was found in regards to retinal arterial blood flow, which was 9.3 ± 2.4 and 12.3 ± 3.2 µl/min in the patient and control group, respectively (p < 0.001). In retinal veins, the difference was less pronounced with values of 10.4 ± 3.8 µl/min in patients and 12.9 ± 2.6 µl/min in control subjects (p < 0.01). Mean retinal arterial diameter was reduced in patients (76.0 ± 8.9 µm vs. 80.6 ± 8.0µm, p = 0.03). No difference in the vasodilatory response to flicker light was observed.

Conclusions : In patients with MCI and AD, retinal blood flow and arterial vessel diameters were reduced compared to healthy age- and sex-matched controls. No difference was found in flicker response between groups. This indicates alterations in retinal blood flow in patients with neurodegenerative disease. Longitudinal studies are required to assess whether ocular blood flow measurements may serve as a potential biomarker to identify high-risk patients.

This is a 2020 ARVO Annual Meeting abstract.