Posterior vitreous detachments (PVDs) are common. Their complications--retinal detachment--however, are comparatively rare. PVDs without complications and those prone to complications can be differentiated biomicroscopically by morphological signs, that is by examining the posterior hyaloid and its insertion at the posterior border of the vitreous base. PVD without complications is a rhegmatogenous detachment which has been completed temporarily as well as anatomically. It has the shape of a collapsed bag whose posterior wall has been perforated and whose contents have been emptied through the hole. All other shapes of PVD are prone to complications: either an incomplete rhegmatogenous PVD with persistent vitreoretinal adhesions; or a non-rhegmatogenous PVD whose complications depend on the retinal or vascular disease which caused it.