We retrospectively investigated the relationship between the appearance of IS/OS line on OCT images and visual acuity after resolution of DME by vitrectomy. Postoperative visual acuity of eyes with complete IS/OS after resolution of DME was significantly better than that without complete IS/OS, though macular edema was completely resolved in both groups. To evaluate the correlation between photoreceptor layer status following resolution of diabetic macular edema (DME) by pars plana vitrectomy (PPV) and final visual acuity (VA). We retrospectively studied a series of 69 eyes from 58 patients with DME who were treated with PPV. Of the 69 eyes, 37 that were examined by optical coherence tomography (OCT) for at least 6 months and that showed a final macular thickness of less than 250 microm were included in this study. We assessed the integrity of the photoreceptor inner and outer segments (IS/OS) line in the fovea, using OCT in relation to their VA and other characteristics. There were no differences in initial VA or in foveal thickness between eyes with or without complete IS/OS at final observation. However, final VA without complete IS/OS was significantly poorer (P = 0.004). VA had improved by more than 2 lines in eight of ten eyes with complete IS/OS and in ten of 27 eyes without complete IS/OS; the groups differed significantly with regard to this percentage (P = 0.03). The postoperative photoreceptor status of the fovea is closely related to the final VA after resolution of DME by PPV.