Pars plana vitrectomy was performed on 19 eyes with idiopathic full-thickness macular holes (6 eyes at stage 2, 8 eyes at stage 3, and 5 eyes at stage 4). Factors affecting postoperative visual prognosis were evaluated. Preoperatively a potential acuity meter (PAM) and laser interferometry were used to predict postoperative visual acuity. Resolution of the surrounding fluid cuff and flattening of the macular holes were obtained in 9 eyes (47%). Eight eyes (42%) gained an improvement in visual acuity of 2 lines or more. Most eyes with anatomical success showed functional improvement. Eyes with short duration of macular holes were considered to have better visual postoperative prognosis. The stage of macular holes, however, had no relationship with postoperative visual acuity. Preoperative measurement with laser interferometry was relatively well correlated with postoperative visual acuity (r = 0.54, p = 0.07), but the results of PAM and preoperative visual acuity had poor correlation.