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Qingyuan Liang, David T. Wong, Huiyuan Liang; The Retinal Venous Laminar Flow in Fluorescein Angiography May Be a Permanent Phenomenon. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2161.
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The retinal venous laminar flow can be observed at the early venous filling in fluorescein angiography. It is known as a temporal phenomenon starting 2-3 seconds after arterial filling and lasts several seconds until complete venous filling. This study aims to explore the venous flow in the whole angiographic process.
A retrospective observational descriptive study was based on fluorescein fundus angiography of 74 eyes (74 patients, 35 males, 39 females, mean age 73.8±13.1 years, age range 38-96 years). Digital angiography was done by a fundus camera (Zeiss FF450 plus) with a digital sensor (Kodak Megaplus). During angiography, the flash exposure was adjusted so that the brightness of fluorescein dye in the venous flow was appropriate to be evaluated. All images were taken with standard field 1 (optic disc at center) and 2 (macular at center) immediately after the rapid intravenous injection of fluorescein sodium, then at 5 and 10 minutes. The vein branches showing laminar filling was first identified on the early phase images, then the existence of the laminar flow in the same branches was examined on the 5- and 10-minute images.
The venous laminar flow appeared in the vein branch after being joined by one or more lower branches at the bifurcations from early venous filling (Fig 1A). The laminar flow maintained the same pattern until the end of the angiography (5 or 10 minutes) (Fig 1B). The phenomenon was observed on at least one vein branch with proper fluorescein brightness in all 74 eyes.
Different from previous knowledge, the venous laminar flow exists in the whole angiographic process, thus is probably a permanent phenomenon. It suggests a possibility that venous flows from lower branches do not mix immediately after draining into the upper branches, but flow separately for certain distance. The key to reveal this phenomenon is proper flash exposure achieved by digital angiography. Further study is necessary to understand the mechanism of this phenomenon.
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