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Qingyuan Liang, Huiyuan Liang, David Wong; Venous Collateral Circulation between Superior and Inferior Halves of the Retina May Be Normal Cross-raphe Drainage. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1556.
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Retinal venous collateral was initially defined as the vessels which mostly developed after branch retinal vein occlusion (BRVO) in the framework of existing retinal vascular network, and originated from the retinal capillary bed, joining obstructed to nonobstructed adjacent vessels, or by-passing obstructions in a single vessel. Recently, this type of collateral between superior and inferior arcades was observed on normal human retina with functional imager (RFI). Retinal artery occlusion (RAO) is a unique situation which eliminates venous filling from the occluded supplying artery in fluorescein angiogram, thus revealing the potential filling from the other sources. This study is to investigate if the possible venous collaterals can be demonstrated in RAO and then compare them to those in BRVO if the collateral exists.
A case-series study was done to retrospectively analyze the fluorescein angiograms of 60 branch or central RAO and 441 BRVO eyes.
In RAO, 21 eyes (35%, OD 15, OS 6) showed 1 or more venous vessels in the non-perfusion retina with cross-raphe fluorescein filling. The vessels were all branches from the superior or inferior vein trunks and mostly temporal to the macula. They were connected via the capillary network near the horizontal raphe to the corresponding veins from the opposite vein trunks in the non-occluded retina. The filling was from the veins in the normal retina to the capillaries at raphe and drained into the collateral vessels in the occluded retina. In BRVO, 276 eyes (63%, OD 150, OS 126) showed venous collaterals which were similar in formation and location to those in RAO but appeared more dilated and tortuous.
The venous collaterals in RAO eyes appear to be normal vein branches. The possibility exists that the collateral circulation is pre-existing cross-raphe drainage in normal eye although this study cannot rule out that it developed after RAO. In BRVO, such collaterals are more prominent due to visualization of the dilated capillary and veins.
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