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Huiyuan Liang, Qingyuan Liang, Shelley R. Boyd; The Anatomical Distribution of Macular and Non-macular Vein Blocking Arteriovenous Crossings. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1000.
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A retrospective case-series study was done on fundus images of 232 non-BRVO eyes of 116 samples (male: 66, female: 50, age: 17-89 years, mean age: 46.5±12.1 years) between 2004 to 2011. A digital grid with coordinate and concentric circles was superimposed on the images. Within 4.5 disc diameters from the optic disc center in the temporal quadrants, the AV crossings with similar features to the BRVO crossings (1st-, 2nd-order arteries and 1st-, 2nd-order veins) identified in previous study were selected. The M and N crossings between the eyes and temporal quadrants were compared.
There were in all 1504 (OD: 734, 48.8%; OS: 770, 51.2%) crossings. 782 (52%) were M crossings (OD: 372, 47.6%; OS: 410, 52.4%) and 722 (48%) were N crossings (OD: 362, 50.1%; OS: 360, 49.9%). The quadrant distribution of M crossing was 21.6% in OD, 23.3% in OS superotemporally and 26% in OD, 29.2% in OS inferotemporally. The N crossings were 27.8% in OD, 26.5% in OS superotemporally and 22.3% in OD, 23.4% in OS inferotemporally. There was no significant difference between the number of M and N crossings in the eyes and quadrants.
The distribution of the M and N crossings was symmetrical between both eyes and temporal quadrants. This is different from the asymmetrical distribution in BRVO and suggests that the prevalence of the M crossings in BRVO is unlikely an effect of anatomical distribution.
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