Table 3.

The updated Retina Society Classification (1991). The revised classification incorporated changes proposed by the Silicone Study Group [10] and modifications proposed also by other authors [12]. Three grades of supposed increasing severity were described, emphasizing the posterior and anterior locations of proliferation. The new classification kept grades A and B, modified grade C, and eliminated grade D. According to the Silicone Study Classification, a more detailed description of grade C (posterior and anterior) PVR was made by adding the types of contraction, the extent of which was detailed by using clock hours instead of quadrants. Modified from [11].

The updated Retina Society Classification [11]
Grade and type	Clinical signs
A	Vitreous haze, pigment clumps, and pigment clusters on inferior retina
B	Wrinkling of inner retinal surface, retinal stiffness, vessel tortuosity, rolled and irregular edge of retinal break, and decreased mobility of vitreous
CP (posterior) (i) Type:  (a) Focal  (b) Diffuse  (c) Subretinal	Full-thickness retinal folds or subretinal strands posterior to equator (1–12 clock hours involvement) (i) Starfolds posterior to vitreous base (ii) Confluent starfolds posterior to vitreous base; optic disc that may not be visible (iii) Proliferation under the retina; annular strand near disc; linear strands; moth-eaten-appearing sheets
CA (anterior) (i) Type:  (a) Circumferential  (b) Anterior	Full-thickness retinal folds or subretinal strands anterior to equator (1–12 clock hours involvement), anterior displacement, and condensed vitreous strands (i) Retina contraction inwards at the posterior edge of the vitreous base; with central displacement of the retina; peripheral retina stretched; posterior retina in radial folds (ii) Snterior contraction on the retina at the vitreous base; ciliary body detachment and epiciliary membrane; iris retraction