Fig. 28. Proliferative vitreoretinopathy grade C. Type 4 circumferential contraction with proliferation immediately behind insertion of the posterior hyaloid pulling retina centrally, stretching the retina anterior to it, and creating radial folds posteriorly. Schematic drawing of situation in nonvitrectomized eye (left) and vitrectomized eye (right). Arrows show direction of pull. (Machemer R, Aaberg TM, Freeman HM et al: An updated classification of retinal detachment with proliferative vitreoretinopathy. Am J Ophthalmol 1991;112:159)