['To analyze the long-term effects of pars plana vitrectomy for diabetic macular edema.', 'Sixty-nine patients (73 eyes) with diabetic macular edema were examined retrospectively after pars plana vitrectomy. The mean follow-up time was 24.6 +/- 7.3 months.', 'The postoperative best-corrected visual acuity (BCVA) at 12 months was significantly better than the preoperative BCVA, and the improvement was maintained for at least 24 months. The mean central retinal thickness (RT) at 3 months after surgery was significantly thinner than the preoperative central RT, and was maintained for at least 24 months in the cases followed for this period. The postoperative BCVA was significantly worse than the preoperative BCVA at 2 years after surgery in eyes with a preoperative BCVA of < or =0.05. In addition, there was lower probability that the postoperative BCVA would be > or =0.5 in eyes with a preoperative BCVA of <0.3.'] Do long-term follow-up results of pars plana vitrectomy for diabetic macular edema?