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Table 1 Studies of retinal blood flow changes in cerebral pathology

From: Retinal blood flow in critical illness and systemic disease: a review

Cerebral studies Species Imaging modality Pathology Metrics measured Findings
Frost et al. [94] Human Retinal photograph—Merge EyeScanner Camera Stroke Retinal vessels widths Positive correlation between width of arterioles/venules and carotid disease in stroke patients
Kwapong et al. [95] Human OCTA—RTVue XR Avanti SD-OCT, Optovue PD Retinal vessel density of SRCP and DRCP
Macula and RNFL thickness
Decreased retinal microvascular density, thinner macula, macular GCIP and inferior RNFL in PD
Querques et al. [97] Human DVA—Imedos Systems UG
OCTA—Cirrus 5000 with Angioplex, Carl Zeiss Meditech
OCT—SPECTRALIS HRA + OCT device, Heidelberg
MCI and AD Retina artery and venous changes
Perfusion density
GCL thickness
DVA found arterial dilation decreased in the AD group compared with MCI and control groups and decreased vessel reaction in AD and MCI groups compared with control
No differences in OCTA
GCL thickness reduced in central and temporal sectors of AD patients compared with controls
Kwa [105] Human Retinal photograph—Optimed, Inc
MRI—1.5 T Magnetom 63 SP/4000, Siemens AG
Cerebral SVD Retinal arterial narrowing, crossings, sclerosis, tortuosity
Presence of WML or lacunar infarcts
92% of patients with cerebral SVD had at least one retinal vascular abnormality
Retinal arterial abnormalities correlated with MRI signs of cerebral SVD
Ong et al. [127] Human Retinal fundus photographs Ischaemic stroke Retinal vasculature pattern/geometry Ischaemic stroke patients had lower fractal dimensions, greater tortuosity and narrower arteriolar calibres compared to healthy controls
Lee et al. [128] Human OCTA—Cirrus HD-OCT Carotid Stenosis Retinal vessel density of DVP Vessel density of the DVP increased in both eyes, 1 month following treatment
Jiang et al. [102] Human Retinal functional imager—Optical Imaging Ltd., Israel
OCT—Cirrus, Carl Zeiss Meditech, CA
MCI and AD Retinal blood flow rate/velocity
GCIPL thickness
Macular blood flow rate was significantly lower in AD patients than MCI and controls, and also significantly lower in MCI patients than controls. Blood flow velocity of arterioles was significantly lower in MCI than controls
GCIPL thickness was significantly reduced in AD and MCI patients than controls
Bulut et al. [103] Human OCTA—RTVue XR100-2, Optovue, CA AD Retinal vascular density
FAZ area. Choroidal thickness
AD patients had significantly lower vascular density than control group
FAZ area was significantly enlarged in AD patients compared with controls
Choroidal thickness was significantly lower in AD patients than controls
Zhang et al. [104] Human RTVue-XR OCT Avanti System—Optovue Inc, CA Early AD and amnestic MCI Retinal vessel/vessel length density
Adjusted flow index
FAZ area
RNFL thickness
Patients showed a significant decrease in the parafoveal SRCP vessel density and adjusted flow index compared with controls, but not in vessel length density
No difference in FAZ area between groups
No significant difference in any measures in the superficial vascular complex
Lahme et al. [129] Human OCTA—RTVue XR Avanti with AngioVue AD Retinal and optic nerve head flow density Flow density of the macula was significantly lower in AD patients than controls, found to be associated with vascular cerebral lesions in AD
Abraham et al. [130] Human OCTA (manufacturer not specified) At-risk MCI Retinal vessel density No significant association of retinal vessel density with cognitive function or risk of MCI
Wang et al. [131] Human Retinal functional imaging—Optical Imaging Ltd, Israel MS Retinal blood flow velocity Reduced blood flow in MS patients with and without optic neuritis compared with healthy controls
Yilmaz et al. [132] Human OCTA—Nidek’s RS-3000 MS FAZ area
Retinal vessel density
No difference in FAZ or perimeter, but lower macular vessel density in MS patients than healthy controls and in MS patients with optic neuritis compared to MS patients without optic neuritis
Lanzillo Cennamo, & Criscuolo [133] Human SD-OCT—RTVue-100 OCT, Optovue Inc
OCTA—Optovue Angiovue System, Optovue Inc
MS with a history of optic neuritis Retinal vessel density
RNFL and GCL thickness
RNFL and GCL thickness and vessel density were lower in the MS group (with and without optic neuritis) than the control group
Beare and Harding [134] Human FFA—Topcon 50-EX, Topcon Cerebral malaria Retinal blood flow
Tissue perfusion
BRB integrity
82% of patients with cerebral malaria had perfusion abnormalities, including capillary nonperfusion, blocked retinal vessels, retinal ischaemia, intravascular filling defects and fluorescein leakage
Dallorto et al. [135] Human OCT and OCTA—RTVue XR Avanti Pituitary adenoma with optic neuropathy RNFL and ganglion cell complex thickness
Vessel density
Vessel density, RNFL thickness and ganglion cell complex thickness were all decreased in pituitary adenoma patients with optic neuropathy compared to healthy eyes
Suzuki et al. [136] Human OCTA—DRI OCT Triton Plus Chiasmal compression band atrophy Vessel density
Those with band atrophy showed smaller average vessel density than controls, which had a strong correlation with RNFL thinning
Lee et al. [137] Human OCTA—DRI OCT Triton Plus Pituitary tumour chiasmal compression Vessel density
RNFL and GCL thickness
Before tumour removal, vessel densities, RNFL and GCL thickness were all reduced in eyes with chiasmal compression compared with healthy controls
  1. Summary of studies investigating retinal blood flow and microvascular changes in cerebral pathology
  2. OCTA, optical coherence tomography angiography; OCT, optical coherence tomography; SD-OCT, spectral-domain OCT; PD, Parkinson’s disease; SRCP, superficial retinal capillary plexus; DRCP, deep retinal capillary plexus; DVP, deep vascular plexus; RNFL, retinal nerve fibre layer; GCIPL, ganglion cell layer and inner plexiform layer; DVA, dynamic vessel analyser; MCI, mild cognitive impairment; AD, Alzheimer’s disease; GCL, ganglion cell layer; MRI, magnetic resonance imaging; SVD, small-vessel disease; WML, white matter lesions; FFA, fundus fluorescein angiography; BRB, blood–retina barrier; MS, multiple sclerosis