It is difficult to diagnose PVR when there is media opacity due to corneal, lenticular, or vitreous opacities. In such cases, ultrasonographic characteristics showing funnel-shaped RD with the opposition of the posterior retina or the presence of an anterior membrane bridging the mouth of the funnel can provide evidence for a diagnosis After diagnosis, PVR should be classifi ed according to the commonly used system presented in Table 21.1 . This system distinguishes between anterior and posterior forms of PVR, and identifi es proliferation a diffuse, focal, or subretinal. While this system provides information on the anatomical construction of PVR, it does not indicate the biologica activity or prognostic factors.