Evaluation of Ocular Perfusion in Alzheimer’s Disease Using Optical Coherence Tomography Angiography

Abstract

Background: There is increasing evidence for the involvement of cerebrovascular factors in Alzheimer's disease (AD). Objective: To evaluate retinal and optic nerve head perfusion in patients with AD using optical coherence tomography angiography (OCTA), and to analyze the correlations of quantitative OCTA metrics with AD pathology and vascular cerebral lesions in AD patients. Methods: 36 eyes of 36 patients with AD (study group) and 38 eyes of 38 healthy subjects (control group) were prospectively included in this study. OCTA was performed using RTVue XR Avanti with AngioVue. In addition, patients underwent a detailed ophthalmological and neurological examination including Mini-Mental State Examination, cerebral magnetic resonance imaging, and amyloid-␤ (A␤) and tau levels in the cerebrospinal fluid (CSF). Results: The flow density in the superficial retinal OCT angiogram of the macula in the study group was significantly lower compared to the control group (p = 0.001). There was a significant correlation between the flow density in the superficial retinal OCT angiogram of the macula, as measured using OCTA, and the Fazekas scale (Spearman's correlation coefficient = -0.520; p = 0.003). There was no significant correlation between the A␤ or tau levels in the CSF and the flow density data. Conclusion: Patients with AD showed a reduced flow density in the radial peripapillary capillaries layer and in the superficial retinal OCT angiogram when compared with healthy controls. The reduced retinal flow density measured using OCTA is not specifically associated with AD pathology but is associated with the vascular cerebral lesions in AD.

Retinal Microvascular Alterations in Alzheimer’s Disease and Mild Cognitive Impairment

“…We showed that AD participants have a sparser VD of the SCP compared with control participants. Our ndings support most of the previous OCTA studies in AD participants (Table 4), [12][13][14]16] which is in keeping with studies on larger retinal vessels using fundus photographs. [3,33] It should be noted that two other studies did not observe any differences in the VD of the SCP in AD participants.…”

“…[10] While there are a few OCTA studies investigating AD, there have been mixed conclusions. [11][12][13][14][15] Some researchers reported nding signi cant reduction in the vessel density (VD) only in the super cial plexus, [14,16] which complements histology ndings [10] and OCT studies [9] since the super cial plexus mainly supplies the inner retinal layer. [17] However, others reported nding changes only in the deep plexus.…”

“…Four OCTA studies have investigated DCP VD in AD individuals, but there is generally a lack of agreement between studies (Table 4). Two studies [11,15] showed a signi cant reduction in VD in AD individuals whereas the others [14,16] did not observe any differences. Obtaining accurate OCTA metrics from the DCP layer is particularly challenging as it is affected by the physiologic variability of FAZ [18,19] and projection artefacts.…”

“…[39] Second, while Zabel et al removed the projection artefacts in the DCP, [11] the rest did not. [14][15][16] In the current study, we quanti ed the VD of the DCP without the in uence of FAZ and projection artefacts, which hopefully reduced measurement bias. We found a sparser VD of the DCP in AD participants but not in MCI individuals, which suggests the possibility of using the VD of the DCP to discriminate between (both SCP and DCP affected) and MCI (only SCP is affected) individuals.…”

Quantitative Assessment of Retinal Thickness and Vessel Density Using Optical Coherence Tomography Angiography in Patients with Alzheimer’s Disease and Glaucoma

“…They found a reduction in the density of vessels in SVP in the eyes of AD compared to HC [18]. Subsequent research groups con rmed a decrease in retinal vascular density in SVP in patients diagnosed with AD [46][47][48]. Jiang et al found a slight decrease in GC-IPL thickness in AD compared with MCI and HC.…”