Since Liebreich's1description in 1871 of an aberrant retinal vessel in the human vitreous, this anomaly has been reported about thirty-two times. The terms prepapillary or preretinal artery and vascular or spiral loop in the vitreous have been used interchangeably to denote an apparently patulous vessel in the form of a variously shaped loop, more often artery than vein, having its origin and termination in the disk or its immediate vicinity and projecting for a variable distance into the vitreous. After Friedrich Müller's classic description of the persistent hyaloid artery in 1856 and of its microscopic structure ten years later by Meissner, there followed abundant reports, not only of its significance, but of blood-containing vessels in various parts of its course. The accepted notion of the hyaloid system included the presence of both artery and vein. In his case, Liebreich saw an arterial loop on the disk which appeared