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Richard P. Stodtmeister, Wolfram Goehler, Lutz E. Pillunat; Functional Model of the Central Retinal Vein Demonstrates Basical Causes of its Pulsation. Invest. Ophthalmol. Vis. Sci. 2012;53(14):257.
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In the vast majority of healthy subjects the central retinal vein pulsates on or in the immediate vicinity of the optic disc. Clinical studies have shown that the absence of a pulsation of the central retinal vein (CRV) is closely associated with primary open angle glaucoma. Therefore, the presence or absence of such a pulsation may be of clinical interest. Conflicting theories try to explain the cause of the presence for this pulsation or its absence. For clarification and in order to test some predications of these theories we built a functional model eye with an artificial CRV.
Methods: Model eye: container 34.6x25.0x14.0 cm. Walls: Clear polystyrene panels, thickness 5 mm. Model of the central retinal vein (MCRV): Black natural rubber latex tube, wall thickness: 60 µm, length: 14.8 cm, round lateral cut (RLC): 7.1 cm² (RFSU AB, Kista, Sweden). Hoses and couplings: Garden irrigating system (Gardena Tricoflex: Minimal RLC: 60.8 mm²). Model blood: Water. Model vitreous: Water. Model intraocular pressure (Model IOP), inflow height, outflow height were variable by the height of the buckets connected to the model by flexible but not collapsible tubes. The model eye was crossed by a not collapsible tube from the right to the left side. A part (length: 14.8 cm) of this tube was removed and replaced by the model vein. Recording of the model vein during changes of variables by digital video camera.
Three main parameters determine the pulsation: inflow, outflow resistance and IOP. Inflow constant: Model IOP high: pulsation. Model IOP low: no pulsation. Outflow resistance high: no pulsation. Outflow resistance low: pulsation. The changes are demonstrated by lowering and lifting the buckets. The effects are clearly seen in the videoclips which will be displayed on a liquid cristal display.
The theory of the Starling resistor may be sufficient to explain the presence or absence of the pulsation of the central retinal vein. Unequal amplitudes of the oscillations of the intracranial pressure and of the intraocular pressure postulated by different theories may not be necessary in the explanation of the pulsation of the central retinal vein. In addition: inspite of the physical limitations of our model the recordings may be of help in understanding the basic process of making the central retinal vein pulsate.
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