Three-dimensional optical coherence tomography evaluation of vascular changes at arteriovenous crossings.

PURPOSE To study the three-dimensional morphologic features of retinal arteriovenous crossings with optical coherence tomography (OCT) and elucidate the vascular changes associated with crossing phenomena as seen on fundus photographs. METHODS We examined 150 consecutive eyes with no ocular disease. In each eye, fundus photographs were taken, and one randomly selected arteriovenous crossing was examined by OCT. The OCT analysis was performed by using sequential thin sections along and perpendicular to the retinal vessels. RESULTS The OCT analysis of these arteriovenous crossings showed that the veins abruptly changed their directions to pass the artery and frequently displayed focal luminal narrowing with no compression or flattening. The OCT measurements revealed that the veins narrowed by 21.0% ± 12.9% at the crossings. The degree of narrowing correlated positively with the diameter of the crossing arteries (r = 0.419, P < 0.001). On fundus photographs, crossing phenomena were observed in 103 of the 150 selected crossings. Venous narrowing measured by OCT was more severe in eyes with crossing phenomena on fundus photographs (P < 0.001). Four types of crossing phenomena were observed: concealment, tapering, deflection, and humping. Venous narrowing rates were similar among all four types. Although the subjects with deflection or humping phenomena were more likely to suffer from hypertension, the mean venous narrowing rate at such crossings was similar to that observed with the other crossing phenomena. CONCLUSIONS Arteriovenous crossings exhibited focal narrowing of the venous lumen with no compression or flattening. Increased venous narrowing and larger arteries were observed at crossings with crossing phenomena.