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Huiyuan Liang, Shelley R. Boyd, David T. Wong, Qingyuan Liang; Are Arteriovenous Crossings Distributed Symmetrically?. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3618.
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© ARVO (1962-2015); The Authors (2016-present)
One previous study found shorter mean distance of retinal arteriovenous (AV) crossings to optic disc center and more vein-posterior crossings in 3-disc diameter (DD) radius around the optic disc in the superotemporal quadrant. This asymmetric distribution was related to more branch retinal vein occlusion (BRVO) in the same quadrant. Based on our observation that BRVO could be up to 3-4 DD from the disc, this study was to evaluate the crossing distribution in a 4-DD radius in the temporal quadrants.
A digital grid with coordinate and concentric circles was superimposed on the digital fundus images (Fig 1) of 184 eyes (92 patients, 45 men, 47 women, mean age 53.6±14.5 years, range 20-83 years) without retinal vascular diseases. In a 4-DD radius around the optic disc, the number of all visible AV crossings, the vascular pattern (vein-posterior or vein-anterior) and distance to the optic disc center were evaluated. The u-test was done for the comparison between the supero- and infero-temporal quadrants.
The result below were ordered in supero-, infero-temporal quadrants of right eye and left eye respectively. The total numbers of the crossings were 907, 902, 913, and 903. The mean numbers of the crossings were 9.9±3.3, 9.8±2.8, 9.9±3.2, 9.8±2.8 (P>0.25). The percentages of the crossings in each DD zone (0-1; 1-2; 2-3; 3-4 DD) were 8%, 19%, 36%, 38%; 8%, 16%, 30%, 45%; 9%, 21%, 35%, 36%; 8%, 18%, 33%, 41%. The mean distances to the optic disc center were 2.6±0.9, 2.7±0.9, 2.6±1.0, 2.6±1.0 DD (P<0.025). The vascular pattern could be identified in about 60% crossings in right eye and 50% in left eye. Among the identified crossings, the mean numbers of the vein-posterior crossings were 3.9±2.0, 3.8±1.9, 3.3±1.6, 3.4±1.6 (P>0.25) and the percentages were 64%, 59%, 65%, and 66%.
Although the number and distance of the crossing in a 4-DD area were similar, symmetrical distribution of the crossing could not be concluded due to statistical discrepancy. Further study is needed.
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