The vitreous humor is a jelly-like substance filling the inside of the eyeball that gradually degenerates and liquefies with age. There are attachments of the vitreous to the retina at various points, including the macula and the optic nerve.

As the vitreous liquefies, it can detach from the macula and optic nerve. Posterior vitreous detachments (PVD) occur in about 25 percent of people in their sixties, and in up to 65 percent of people in their eighties. Vitreous detachment (PVD) is slightly more common in women.

Symptoms include flashes followed by a large floater.  Although initial symptoms can scare or concern a patient, PVD is a benign condition and treatment is not necessary.