To evaluate the effectiveness of laser photocoagulation as adjuvant therapy in the treatment of large macular holes.A randomized clinical trial. Thirty-one eyes from 29 subjects with idiopathic macular holes of diameters larger than 400 microm were randomized into a laser group and a control group. All eyes underwent vitrectomy with peeling of the internal limiting membrane. Contrary to the control group eyes, the laser group eyes underwent laser photocoagulation at the center of the macular hole before vitrectomy. Visual acuity and anatomic outcomes assessed by optical coherence tomography (OCT) were analyzed 3 months after surgery.On postoperative OCT, closure of the macular hole was noted in 17 of the 18 (94.4%) laser group eyes and 10 of the 13 (76.9%) control group eyes. Hole closure without bare retinal pigment epithelium was observed in 16 eyes in the laser group and 6 eyes in the control group (P < 0.05). The amount of improvement in logMAR visual acuity 3 months after surgery was 0.40 +/- 0.29 in the laser group, and 0.19 +/- 0.23 in the control group (P < 0.05).Laser photocoagulation constitutes a potent adjuvant therapy that may improve anatomical and visual outcomes of surgery for macular holes larger than 400 microm.