Purpose: To investigate the effect of vitrectomy on the treatment of diabetic macular edema (DME) refractory to nonsurgical therapies and to determine the preoperative prognostic factors related to surgical outcomes.
Methods: Seventy-seven eyes from 74 patients who had undergone vitrectomy and macular photocoagulation 2 weeks after vitrectomy for nontractional DME refractory to anti-vascular endothelial growth factor or steroid injection and/or macular grid/focal photocoagulation were included. The eyes were divided into the responsive group (group 1) and the unresponsive group (group 2) according to the postoperative changes in central subfield thickness (CST). The changes in best-corrected visual acuity (BCVA) and CST were compared. Potential preoperative predictors including the size of the foveal avascular zone (FAZ) were assessed.
Results: In group 1 (N = 51), the mean logarithm of the minimum angle of resolution BCVAs at baseline was 0.60 ± 0.30; 6 months after vitrectomy, 0.47 ± 0.28 (vs. baseline, p < 0.001); 12 months after vitrectomy, 0.38 ± 0.28 (vs. baseline, p < 0.001). However, in group 2 (N = 26), no significant change in BCVA was noted. Among the preoperative factors, only the size of the FAZ showed a significant difference between the two groups (0.45 ± 0.17 mm(2) in group 1 vs. 0.59 ± 0.26 mm(2) in group 2; p = 0.020). The enlarged FAZ was also significantly correlated with worse BCVA at the postoperative 6-month follow-up (r = 0.256, p = 0.025).
Conclusions: Vitrectomy is an effective treatment modality for DME refractory to nonsurgical therapies, especially in cases without enlarged FAZ. Preoperative evaluation of the perfusion status of the macula seems helpful to selecting candidates for vitrectomy.
Keywords: Diabetic macular edema; Foveal avascular zone; Macular ischemia; Pars plana vitrectomy.