berrywoo is correct.
Dr. O.
As a patient you actually won't know that you have PVR, unless, after your first detachment the retina keeps detaching.
A doctor however will notice signs of PVR when s/he examines you as there are certain characteristics about PVR.
PVR is basically scar tissue that forms on the retina and will cause traction to pull the retina off from the back of the eye.