Retinal blood flow in mild cognitive impairment and Alzheimer's disease

Gilbert T Feke, Bradley T Hyman, Robert A Stern, Louis R Pasquale, Gilbert T Feke, Bradley T Hyman, Robert A Stern, Louis R Pasquale

Abstract

Background: Patients with Alzheimer's disease (AD) demonstrate the narrowing of retinal veins and decreased retinal venous blood flow compared with control subjects. We assessed whether these abnormalities are present in patients with mild cognitive impairment (MCI).

Methods: After the determination of the global clinical dementia rating, 52 subjects (10 AD, 21 MCI, and 21 normal controls) underwent retinal hemodynamic profiling. Blood column diameter, blood speed, and blood flow were measured in a major temporal retinal vein using retinal laser Doppler flowmetry. In addition, peripapillary retinal nerve fiber layer (RNFL) thickness was measured using optical coherence tomography.

Results: Blood column diameter in AD was narrower than in both MCI (P = .004) and controls (P = .002). However, blood speed in both AD (P = .024) and MCI (P = .005) was lower than in controls. As a result, the differences in blood flow between AD and MCI (P = .036), AD and controls (P < .0001), and MCI and controls (P = .009) were significant. Although there were no differences in RNFL thickness among the groups, blood flow was correlated (P = .047) with superior RNFL thickness in the AD group, but not in the MCI (P = .40) or control (P = .84) groups.

Conclusions: Retinal blood flow in MCI is intermediate between what is measured in control subjects and in AD patients. Our findings suggest that blood flow abnormalities may precede the neurodegeneration in AD.

Keywords: Alzheimer's disease; Mild cognitive impairment; Retinal blood flow; Retinal blood speed; Retinal venous blood column diameter.

Figures

Fig. 1
Fig. 1
Mean values of the retinal venous blood column diameter in subjects with Alzheimer's disease (AD), with mild cognitive impairment (MCI), and in control subjects. Error bars represent one standard deviation. Significance levels for paired comparisons were determined using Fisher's Protected Least Significant Difference (PLSD) tests.
Fig. 2
Fig. 2
Mean values of the retinal venous blood speed in subjects with Alzheimer's disease (AD), with mild cognitive impairment (MCI), and in control subjects. Error bars represent one standard deviation. Significance levels for paired comparisons were determined using Fisher's Protected Least Significant Difference (PLSD) tests.
Fig. 3
Fig. 3
Mean values of the retinal venous blood flow in subjects with Alzheimer's disease (AD), with mild cognitive impairment (MCI), and in control subjects. Error bars represent one standard deviation. Significance levels for paired comparisons were determined using Fisher's Protected Least Significant Difference (PLSD) tests.
Fig. 4
Fig. 4
Retinal venous blood flow plotted as a function of the thickness of the peripapillary retinal nerve fiber layer (RNFL) in the superior retinal quadrant in patients with Alzheimer's disease (AD) (A) with mild cognitive impairment (MCI) (B), and in normal control subjects (C). The values of the Spearman correlation coefficients (rho) and the corresponding P values are shown.

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