Prepapillary vascular loops.

Twenty-one eyes in eighteen patients with prepapillary vascular loops were studied. Fluorescein angiography demonstrated 20 of the loops to be arterial and one to be venous. The wide range of clinical and angiographic variations of prepapillary loops are described. Cilioretinal arteries were seen in 16 of 21 eyes with loops and occasionally provided a major portion of the blood supply to the retina. In addition to the previously described complications of vitreous hemorrhage and branch retinal artery obstruction in eyes with a prepapillary arterial loop, hyphema and amaurosis fugax were notable new associations.