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Q. Liang, D. Wong; Is Angle Pattern of an Arteriovenous Crossing a Risk Factor in Branch Retinal Vein Occlusion?. Invest. Ophthalmol. Vis. Sci. 2009;50(13):100.
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© ARVO (1962-2015); The Authors (2016-present)
To analyze the angle patterns of the arteriovenous crossings as a risk factor in branch retinal vein occlusion (BRVO).
84 eyes of 84 patients with BRVO at an arteriovenous crossing on the superotemporal or inferotemporal vessel arcades were retrospectively studied in a tertiary care hospital. In 79 of the 84 study eyes, a corresponding arteriovenous crossing on the opposite temporal arcade was found and served as control group 1. In 81 of the 84 fellow eyes without BRVO, a corresponding arteriovenous crossing in the same arcade was found and served as control group 2. The angles between artery and vein of the arteriovenous crossings in vein occlusion side were measured on the fluorescein angiographic images, color and red free fundus photographs. The angle patterns were classified as type 1 (0° < angles < 60°) and type 2 (60° ≤ angles ≤ 90°) (Fig. 1). The percentages of each type of angle were compared between study and the two control groups.
There were 80% (67/84) type1 and 20% (17/84) type 2 angles in the study group. In control group 1, 61% (48/79) were type 1 and 39% (31/79) were type 2 angles whereas in control group 2, there were 48% (39/81) type 1 and 52% (42/81) type2 angles. There was statistically significant difference between the study group and control group 1 (P<0.01) and control group 2 (P<0.001).
Smaller angles (type 1) appear more frequently than larger angles (type 2) in BRVO, suggesting the angle pattern may be a risk factor in BRVO. Angle pattern may affect vector portion of artery blood flow against venous blood flow and cause hemodynamic change of venous flow (Fig. 1). Further study is necessary to investigate the quantitative correlation between the exact degree of the angle and occurrence of BRVO.
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