The incidence of lens opacities reported after pars plana vitrectomy for various indications for vitrectomy has varied considerably. Comparison of the different indications for vitrectomy is only partially possible because of a lack of comparable studies. In this prospective study the indications for vitrectomy were investigated: macular pucker and diabetic vitreoretinopathy were compared concerning the postoperative incidence of lens opacities. Nearly twice as many cases of lens opacity occurred after vitrectomy for diabetic retinopathy. Also, the fellow eyes of the patients with diabetic vitreoretinopathy developed lens opacity much more frequently after vitrectomy compared with the fellow eyes of the patients with macular pucker.