To report the use of optical coherence tomography (OCT) for evaluation of diffuse diabetic macular edema (DME) before and after vitrectomy.

Interventional case series.

A retrospective study was made of 15 consecutive eyes of 13 patients that had vitrectomy for diffuse DME and OCT preoperatively and postoperatively. In seven eyes of six patients (group 1), vitrectomy was performed because of vitreomacular traction observed on biomicroscopy or OCT. In the other eight eyes of seven patients (group 2), vitrectomy was performed for DME not responsive to laser photocoagulation, with no vitreomacular traction on biomicroscopy or OCT.

Mean ± standard deviation (SD) follow-up after vitrectomy was 18 ± 10 months (range, 6 to 33 months). In group 1, mean ± SD retinal thickness decreased significantly from 661 ± 181 μm preoperatively to 210 ± 32 μm at the end of follow-up (P = .018). Median best-corrected visual acuity (BCVA) improved from 20/100 before surgery (range, 20/250 to 20/50) to 20/80 at the end of follow-up (range, 20/250 to 20/25; P = .046). In one eye in group 1, vitreomacular traction was only observed on OCT and not on biomicroscopy. In group 2, mean ± SD retinal thickness decreased from 522 ± 103 μm preoperatively to 428 ± 121 μm at the end of follow-up (P = .2). Median BCVA was 20/100 before vitrectomy (range, 20/320 to 20/63) and 20/200 at the end of follow-up (range, 20/250 to 20/63; P = .78).

Vitrectomy was beneficial in eyes with diffuse DME combined with vitreomacular traction but not in eyes without traction. Optical coherence tomography allowed diagnosis of subtle vitreomacular traction and provided precise preoperative and postoperative assessments of macular thickness.