The retina is made up of two main layers:
Posterior vitreous detachment (PVD) occurs when the vitreous separates from the retina, as part of the normal ageing process. Normally PVD does not cause a problem, but if there is an abnormal adhesion to the retina it can tear (rhegma) the retina. A rhegmatogenous retinal detachment occurs if vitreous fluid passes through the tear, separating the neurosensory retina from the retinal pigment epithelium.