The Ocular Circulation
Seiten
2011
Morgan & Claypool Publishers (Verlag)
978-1-61504-168-8 (ISBN)
Morgan & Claypool Publishers (Verlag)
978-1-61504-168-8 (ISBN)
Describes the unique anatomy and physiology of the vascular beds that serve the eye. The need for an unobstructed light path from the cornea to the retina and a relatively fixed corneal curvature and distance between refractive structures pose significant challenges for the vasculature to provide nutrients and remove metabolic waste.
This presentation describes the unique anatomy and physiology of the vascular beds that serve the eye. The needs for an unobstructed light path from the cornea to the retina and a relatively fixed corneal curvature and distance between refractive structures pose significant challenges for the vasculature to provide nutrients and remove metabolic waste. To meet these needs, the ocular vascular beds are confined to the periphery of the posterior two thirds of the eye and a surrogate circulation provides a continuous flow of aqueous humor to nourish the avascular cornea, lens and vitreous compartment. The production of aqueous humor (and its ease of egress from the eye) also generates the intraocular pressure (IOP), which maintains the shape of the eye. However, the IOP also exerts a compressing force on the ocular blood vessels that is higher than elsewhere in the body. This is particularly true for the intraocular veins, which must have a pressure higher than IOP to remain patent, and so the IOP is the effective venous pressure for the intraocular vascular beds. Consequently, the ocular circulation operates at a lower perfusion pressure gradient than elsewhere in the body and is more at risk for ischemic damage when faced with low arterial pressure, particularly if IOP is elevated. This risk and the specialized tissues of the eye give rise to the fascinating physiology of the ocular circulations.
This presentation describes the unique anatomy and physiology of the vascular beds that serve the eye. The needs for an unobstructed light path from the cornea to the retina and a relatively fixed corneal curvature and distance between refractive structures pose significant challenges for the vasculature to provide nutrients and remove metabolic waste. To meet these needs, the ocular vascular beds are confined to the periphery of the posterior two thirds of the eye and a surrogate circulation provides a continuous flow of aqueous humor to nourish the avascular cornea, lens and vitreous compartment. The production of aqueous humor (and its ease of egress from the eye) also generates the intraocular pressure (IOP), which maintains the shape of the eye. However, the IOP also exerts a compressing force on the ocular blood vessels that is higher than elsewhere in the body. This is particularly true for the intraocular veins, which must have a pressure higher than IOP to remain patent, and so the IOP is the effective venous pressure for the intraocular vascular beds. Consequently, the ocular circulation operates at a lower perfusion pressure gradient than elsewhere in the body and is more at risk for ischemic damage when faced with low arterial pressure, particularly if IOP is elevated. This risk and the specialized tissues of the eye give rise to the fascinating physiology of the ocular circulations.
Jeffrey W. Kiel received his Ph.D. in Physiology fromthe University ofTexas Health Science Center at San Antonio in 1987. His early research focused on gastrointestinal vascular regulation, and then in 1990 he changed directions and began studying the eye. He has worked on choroidal blood flow regulation, the role of ciliary blood flow in aqueous production and, most recently, on the regulation of episcleral venous pressure.
Introduction
Anatomy
Blood flow measuring techniques
Ocular perfusion pressure, IOP and the ocular Starling resistor effect
Ocular blood flow effects on IOP
Local control of ocular blood flow
Neural control of ocular blood flow
Summary
| Reihe/Serie | Colloquium Series on Integrated Systems Physiology |
|---|---|
| Verlagsort | San Rafael |
| Sprache | englisch |
| Maße | 191 x 235 mm |
| Gewicht | 180 g |
| Themenwelt | Medizin / Pharmazie ► Medizinische Fachgebiete ► Augenheilkunde |
| Studium ► 1. Studienabschnitt (Vorklinik) ► Physiologie | |
| ISBN-10 | 1-61504-168-0 / 1615041680 |
| ISBN-13 | 978-1-61504-168-8 / 9781615041688 |
| Zustand | Neuware |
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