- Can be arterial or venous.
- Usually congenital and most commonly unilateral.
- Usually gives no symptoms, unless it is complicated with vascular obstruction
- May appear as simple hairpin loops, in a figure eight, or in a corkscrew configuration
- The loops usually project from the optic disc to the vitreous cavity and return to the optic disc
- Can be associated with persistent posterior hyaloid vessel where the loops extend into Cloquet's canal