Emerging Applications of Optical Coherence Tomography Angiography (OCTA) in neurological research

Purpose:To review the clinical and research value of optical coherence tomography angiography(OCTA)in the field of neurology.Methods:Current literature involving OCTA were reviewed through PubMed using the search terms“optical coherence tomography angiography”,with“multiple sclerosis”,“Alzheimer’s disease”,“optic neuropathy”,or other closely-related terms.Results:OCTA has been applied in research to advance our understanding of the pathobiology of neurological disorders.OCTA-derived blood flow and vessel density measures are altered in multiple sclerosis(MS),Alzheimer’s disease(AD),and various optic neuropathies(ON)in varying regions of the posterior segment vasculature of the eye.These emerging research findings support the occurrence of retinal vascular alterations across a host of neurological disorders and raise the possibility that vasculopathy can be clinically relevant since it contributes to the pathobiology of several neurological disorders.Conclusion:OCTA may be beneficial for neurological research.Additional investigations using OCTA in neurological disorders will help to further validate its clinical and research utilities in terms of characterizing the role of vasculopathy in neurological disorders.

Microvascular blood flow velocities measured with a retinal function imager: inter-eye correlations in healthy controls and an exploration in multiple sclerosis

Background:The retinal microcirculation has been studied in various diseases including multiple sclerosis(MS).However,inter-eye correlations and potential differences of the retinal blood flow velocity(BFV)remain largely unstudied but may be important in guiding eye selection as well as the design and interpretation of studies assessing or utilizing retinal BFV.The primary aim of this study was to determine inter-eye correlations in BFVs in healthy controls(HCs).Since prior studies raise the possibility of reduced BFV in MS eyes,a secondary aim was to compare retinal BFVs between MS eyes,grouped based on optic neuritis(ON)history and HC eyes.Methods:Macular arteriole and venule BFVs were determined using a retinal function imager(RFI)in both eyes of 20 HCs.One eye from a total of 38 MS patients comprising 13 eyes with ON(MSON)and 25 eyes without ON(MSNON)history were similarly imaged with RFI.Results:OD(right)and OS(left)BFVs were not significantly different in arterioles(OD:3.95±0.59 mm/s;OS:4.08±0.60 mm/s,P=0.10)or venules(OD:3.11±0.46 mm/s;OS:3.23±0.52 mm/s,P=0.06)in HCs.Very strong inter-eye correlations were also found between arteriolar(r=0.84,P<0.001)and venular(r=0.87,P<0.001)BFVs in HCs.Arteriolar(3.48±0.88 mm/s)and venular(2.75±0.53 mm/s)BFVs in MSNON eyes were significantly lower than in HC eyes(P=0.009 and P=0.005,respectively).Similarly,arteriolar(3.59±0.69 mm/s)and venular(2.80±0.45 mm/s)BFVs in MSON eyes were also significantly lower than in HC eyes(P=0.046 and P=0.048,respectively).Arteriolar and venular BFVs in MSON and MSNON eyes did not differ from each other(P=0.42 and P=0.48,respectively).Conclusions:Inter-eye arteriolar and venular BFVs do not differ significantly in HCs and are strongly correlated.Our findings support prior observations that arteriolar and venular BFVs may be reduced in MS eyes.Moreover,this seems to be the case in both MS eyes with and without a history of ON,raising the possibility of global blood flow alterations in MS.Future larger studies are needed to assess differences in BFVs between MSON and MSNON eyes.