Retinal Artery OcclusionRetinal ArteryRetinal VeinOphthalmic ArteryOphthalmodynamometryVeinsArteriesCiliary ArteriesSusac SyndromeFluorescein AngiographyRetinal VesselsSaphenous VeinUltrasonography, Doppler, ColorRetinal Vein OcclusionRetinal DiseasesPulmonary ArteryFundus OculiPortal VeinVaricose VeinsBlood Flow VelocityCarotid ArteriesFemoral ArteryRegional Blood FlowOrbitRenal ArteryPulmonary VeinsCerebral ArteriesFemoral VeinMesenteric ArteriesCarotid Artery DiseasesCarotid Artery, InternalBasilar ArteryBlindnessJugular VeinsArterial Occlusive DiseasesAmaurosis FugaxLaser-Doppler FlowmetryCarotid Artery, ExternalIntraocular PressureGlaucoma, NeovascularGanglionectomyVentricular Function, LeftCoronary Artery BypassIliac ArteryVisual AcuityVertebral ArteryMammary ArteriesEyeOptic DiskRadial ArteryBlood PressureSubclavian ArterySneddon SyndromeRenal VeinsMesenteric VeinsVasodilationMyographyVentricular Dysfunction, LeftIliac VeinParacentesisChoroidUmbilical VeinsCoronary VesselsRetinal NeuronsHepatic ArterySplenic ArteryEye DiseasesEndothelium, VascularVasoconstrictionTreatment OutcomeBrachial ArteryMuscle, Smooth, VascularRetinaOptic Neuropathy, IschemicCarotid Artery, CommonHepatic VeinsMethyldopaEisenmenger ComplexEmbolismProspective StudiesPopliteal VeinVasodilator AgentsRetrospective StudiesFollow-Up StudiesCeliac ArteryNitroarginineMesenteric Artery, SuperiorUmbilical ArteriesCarotid StenosisHypertrophy, Left VentricularThoracic ArteriesSubclavian VeinSplenic VeinPopliteal ArteryOphthalmoscopyMiddle Cerebral ArteryRenal Artery ObstructionCerebral VeinsMuscle RelaxationTime Factors