To evaluate the ability of spectral-domain optical coherence tomography (SD-OCT) images of the inner/outer segment (IS/OS) junction to predict macular hole surgery outcomes. Fifty-four eyes in 53 patients with idiopathic macular holes were studied. Postoperative visual acuity and SD-OCT images of the fovea were examined before and 12 months after surgery. The total area and the maximum length of the IS/OS junction defect were measured. The macular holes were successfully closed in all the eyes included in this series. The mean log MAR visual acuity improved significantly from 0.67 +/- 0.25 preoperatively to 0.16 +/- 0.22 postoperatively (p < 0.001). The mean total area and maximum length of the IS/OS junction defect at 12 months after surgery were 10,185 +/- 1,537 microm(2) and 100.5 +/- 10.4 microm respectively; these values were significantly negatively correlated with the postoperative visual acuity. SD-OCT is useful for quantitatively measuring IS/OS junction defects. The postoperative IS/OS junction may play an important role in visual recovery after macular hole surgery.