What happens in case of a posterior vitreous detachment?

At a young age the vitreous humor is completely transparent. The aging of the eye degenerates the vitreous humor and partially liquefies it. At the age of 50 – 60 the structure of the vitreous humor partially collapses. This posterior vitreous detachment often coincides with an increase of floater disturbances caused by the Weiss or Martegini ring. This ring is a structure in the vitreous humor. It fixes the vitreous humor to the visual nerve. The shrinking of the vitreous humor described above causes it to detach from the visual nerve and freely float before the retina. The shadow caused by this condition is disturbing for the patient and is called floater or mouches volantes.