A model for pulsatile and steady ocular blood flow. 1995

C E Krakau
Department of Ophthalmology, University Eye Clinic, Malmö, Sweden.

BACKGROUND The aim was to elucidate two controversial questions. (1) is the pulsatile inflow dominant or is there a sizeable steady inflow component? (2) Is the outflow of blood steady or pulsatile in induced and in glaucomatous hypertension? METHODS The OBF system (Langham) was used for pulse recording. A simple electric flow model was conceived and analysed in terms of Fourier series, using linear circuit theory. CONCLUSIONS Possible explanations of the seemingly inconsistent observations are indicated by the model. (1) A steady inflow of similar magnitude to the pulsatile one is predicted. The total flow can be determined at present theoretically from recordings of the pulsatile inflow and of the systolic and diastolic intraocular blood pressure. Some methodological improvements are desirable in order to obtain reliable estimates in practice. (2) The outflow is normally steady, probably even in ocular hypertension and glaucoma. In hypertension induced with the suction cup this may be doubted. The eye has similarities with the device called the Starling resistor which describes the behaviour of collapsible vessels. Acute pressure increase (plus the pulsations of the IOP) may put the collapsible vessels into a state which disturbs the steady outflow. The effects of changes in IOP and in other components on the size and shape of the flow curve are demonstrated.

UI MeSH Term Description Entries
D007429 Intraocular Pressure The pressure of the fluids in the eye. Ocular Tension,Intraocular Pressures,Ocular Tensions,Pressure, Intraocular,Pressures, Intraocular,Tension, Ocular,Tensions, Ocular
D008954 Models, Biological Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment. Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D009798 Ocular Hypertension A condition in which the intraocular pressure is elevated above normal and which may lead to glaucoma. Glaucoma, Suspect,Hypertension, Ocular,Glaucomas, Suspect,Hypertensions, Ocular,Ocular Hypertensions,Suspect Glaucoma,Suspect Glaucomas
D011673 Pulsatile Flow Rhythmic, intermittent propagation of a fluid through a BLOOD VESSEL or piping system, in contrast to constant, smooth propagation, which produces laminar flow. Flow, Pulsating,Perfusion, Pulsatile,Flow, Pulsatile,Flows, Pulsatile,Flows, Pulsating,Perfusions, Pulsatile,Pulsatile Flows,Pulsatile Perfusion,Pulsatile Perfusions,Pulsating Flow,Pulsating Flows
D012039 Regional Blood Flow The flow of BLOOD through or around an organ or region of the body. Blood Flow, Regional,Blood Flows, Regional,Flow, Regional Blood,Flows, Regional Blood,Regional Blood Flows
D001783 Blood Flow Velocity A value equal to the total volume flow divided by the cross-sectional area of the vascular bed. Blood Flow Velocities,Flow Velocities, Blood,Flow Velocity, Blood,Velocities, Blood Flow,Velocity, Blood Flow
D001794 Blood Pressure PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS. Systolic Pressure,Diastolic Pressure,Pulse Pressure,Pressure, Blood,Pressure, Diastolic,Pressure, Pulse,Pressure, Systolic,Pressures, Systolic
D005123 Eye The organ of sight constituting a pair of globular organs made up of a three-layered roughly spherical structure specialized for receiving and responding to light. Eyes
D005583 Fourier Analysis Analysis based on the mathematical function first formulated by Jean-Baptiste-Joseph Fourier in 1807. The function, known as the Fourier transform, describes the sinusoidal pattern of any fluctuating pattern in the physical world in terms of its amplitude and its phase. It has broad applications in biomedicine, e.g., analysis of the x-ray crystallography data pivotal in identifying the double helical nature of DNA and in analysis of other molecules, including viruses, and the modified back-projection algorithm universally used in computerized tomography imaging, etc. (From Segen, The Dictionary of Modern Medicine, 1992) Fourier Series,Fourier Transform,Analysis, Cyclic,Analysis, Fourier,Cyclic Analysis,Analyses, Cyclic,Cyclic Analyses,Series, Fourier,Transform, Fourier
D005901 Glaucoma An ocular disease, occurring in many forms, having as its primary characteristics an unstable or a sustained increase in the intraocular pressure which the eye cannot withstand without damage to its structure or impairment of its function. The consequences of the increased pressure may be manifested in a variety of symptoms, depending upon type and severity, such as excavation of the optic disk, hardness of the eyeball, corneal anesthesia, reduced visual acuity, seeing of colored halos around lights, disturbed dark adaptation, visual field defects, and headaches. (Dictionary of Visual Science, 4th ed) Glaucomas

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