Effect of vitrectomy on macular microcirculation in patients with diffuse diabetic macular edema

To determine whether retinal microcirculatory changes occur after vitrectomy in eyes with diffuse diabetic macular edema (DME), and whether changes in blood flow are associated with visual outcome and the resolution of macular edema.

Thirty-three eyes of 30 consecutive diabetic patients who underwent pars plana vitrectomy for diffuse DME, and 16 eyes of 16 diabetic patients without macular edema, were included. Mean macular blood flows were measured using a Heidelberg Retinal Flowmeter, and central macular thicknesses (CMTs) were determined by optical coherence tomography. Visual outcomes, CMTs, and macular blood flow were evaluated before and 1, 4, 12 weeks after vitrectomy, and compared between eyes with resolved macular edema and those with persistent macular edema.

Mean preoperative macular blood flow in eyes with diffuse DME was higher than in controls (606.5+/-357.9 AU vs 407.1+/-265.9 AU, P=0.021). Mean macular blood flow (422.6+/-247.5 AU) at 12 weeks after vitrectomy was significantly lower than preoperative blood flow (P=0.002), and similar to that of controls (P=0.47). In 22 of the 33 (66.7%) DME eyes, macular edema was resolved at 12 weeks after vitrectomy. The mean ratio of macular blood flow at 12 weeks postoperatively versus the preoperative level was significantly lower in eyes with resolved macular edema than in eyes with persistent macular edema (0.65 vs 1.08, P<0.001).

Increased macular blood flow in diabetic macular edema was normalized after vitrectomy in eyes with resolved macular edema. Changes of macular blood flow may be associated with the resolution of macular edema in diabetic eyes.