Proliferative vitreoretinopathy: pathobiology, surgical management, and adjunctive treatment.

over 75% of cases.5-7 This process is characterised by cellular proliferation on both surfaces of the detached neuroretina, on the posterior vitreous face, and within the vitreous base resulting in the formation of contractile periretinal membranes. It is estimated to occur in 5-10% of all rhegmatogenous retinal detachments.7 Initial clinical observations emphasised cellular activity in, and retraction of, the vitreous together with the appearance of retinal folds. The condition was referred to as massive vitreous retraction (MVR) or massive preretinal retraction (MPR) on the premise of the primary pathology being centred in the vitreous gel.8 This was later modified to massive periretinal proliferation (MPP)9 to acknowledge the role of periretinal membrane formation. A unifying classification was published by the Retina Society Terminology Committee in 1983.7 This used the term proliferative vitreoretinopathy and has served as the basis for subsequent clinical and laboratory studies. It subdivides PVR into four stages (A-D) of increasing severity based on clinical features: vitreous haze and pigment, retinal stiffness and wrinkling, rolled edges of retinal breaks, vascular tortuosity, and fixed retinal folds advancing to a funnel retinal detachment. A revised form of this classification further subdivides the proliferative process by location (anterior/posterior) and type (focal/diffuse/subretinal/circumferential and anterior displacement).' 0 While these classifications have served to standardise the terminology and clinical descriptions used in dealing with PVR they are essentially anatomical and do not address the biological activity of the PVR process. Furthermore, they do not record clinically important information such as the number, size, and location of retinal breaks, factors known to be of significance in the risk of development and progression of PVR." The existing classifications therefore have limitations with respect to the comparison of the biological stage and the level of activity ofthe process between individual eyes in clinical or laboratory studies.