Comparison of Retinal Microvasculature in Patients With Alzheimer's Disease and Primary Open-Angle Glaucoma by Optical Coherence Tomography Angiography

Abstract

PURPOSE. Comparison of retinal microvasculature within the macula and the optic nerve head in the eyes of patients with Alzheimer's disease (AD), primary open-angle glaucoma (POAG), and in a healthy control (HC) group, using optical coherence tomography angiography (OCTA). METHODS. In this cross-sectional study, 27 patients with AD, 27 with POAG, and 27 healthy controls were enrolled. The Mini-Mental State Examination test was used to assess cognitive function. Ophthalmic examination included OCTA, which was used for the imaging of vascular flow within the layer of radial peripapillary capillaries (RPCs), and also in the superficial vascular plexus (SVP) and deep vascular plexus (DVP) of the retina. RESULTS. In the AD group, the density of vessels in DVP was significantly reduced and the foveal avascular zone was increased when compared to POAG and HC groups (P < 0.001). Patients with POAG had a significantly reduced vessel density in RPCs and SVP as compared to AD and HC groups (P < 0.001). The average thickness of peripapillary retinal nerve fiber layer was correlated with the vessel density in SVP in patients with POAG (Pearson's r ¼ 0.66; P ¼ 0.0002) and was significantly lower in POAG and AD groups than in the HC group (P < 0.001). CONCLUSIONS. AD and POAG are neurodegenerative diseases associated with apoptosis of nerve cells and impairment of microvasculature. Despite the fact that in both diseases there are abnormalities of the entire retinal vascular system, significant microcirculatory impairment in POAG patients affects superficial vessels, whereas in AD patients it affects vessels located in the deeper retinal layers.

Retinal analysis of a mouse model of Alzheimer’s disease with multicontrast optical coherence tomography

“…This is contrary to what has been observed in human vessel microangiography studies. 22,23 However, in the previous human studies, the area of interest usually targets the fovea. Since mice do not have a fovea, there is not an equivalent measurement in the mouse retina.…”

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

“…[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.…”

“…[3,33] It should be noted that two other studies did not observe any differences in the VD of the SCP in AD participants. [11,15] OCTA quanti cation metrics may potentially be affected by several confounders. First, OCTA signal strength quality can affect the VD, where the VD decreased linearly with signal strength.…”

“…[17] However, others reported nding changes only in the deep plexus. [11,15] Studies [15,16] have also used OCTA to examine participants with MCI, who are at higher risk for dementia and AD, but have drawn con icting results as well. For example, while Zhang et al [16] found signi cantly decreased VD only in the super cial plexus, Wu et al [15] found a reduction in the VD only in the deep plexus.…”