Vitrectomy for diabetic macular edema: The role of posterior vitreous detachment and epimacular membrane

PURPOSE: To evaluate the surgical efficacy of pars plana vitrectomy on eyes with diabetic macular edema in the presence or absence of a complete posterior vitreous detachment and with or without an epimacular membrane. METHODS: Pars plana vitrectomy was performed on 30 eyes of 29 cases with diabetic macular edema. Visual acuity was measured, and retinal thickness was determined by optical coherence tomography before and after vitrectomy. To evaluate the relationship between the effects of vitrectomy and the presence or absence of posterior vitreous detachment and/or epimacular membrane, all eyes were placed into one of four groups: group A, eyes with posterior vitreous detachment and epimacular membrane; B, eyes with posterior vitreous detachment and without epimacular membrane; C, eyes without posterior vitreous detachment and with epimacular membrane; and D, eyes without posterior vitreous detach, ment and without epimacular membrane. The expression of vascular endothelial growth factor and interleukin-6 was investigated immunohistochemically in epimacular membrane specimens obtained from seven eyes with diffuse diabetic macular edema. RESULTS: The postoperative mean visual acuity (0.653 +/- 0.350: mean +/- SD logarithm of minimal angle of resolution [logMAR]) was significantly better than the mean preoperative visual acuity (0.891 +/- 0.319 log-MAR; Wilcoxon signed-rank test, P = .0007). The postoperative foveal thickness (264.5 +/- 118.6 mum) was significantly thinner than the preoperative foveal thick, ness (477.8 +/- 147.7 mum; Wilcoxon signed,rank test, P < .0001). There were no significant differences in the improvement of visual acuity and decrease of foveal thickness between the four groups (Kruskal-Wallis test, P = .13, P = .65, respectively). All of the epimacular membranes obtained at surgery expressed vascular endothelial growth factor and interleukin-6. CONCLUSIONS: These results demonstrated that vitrectomy with removal of epimacular membrane is generally an effective procedure in reducing diabetic macular edema, and the outcome does not depend on the presence or absence of posterior vitreous detachment and epimacular membrane. (Am J Ophthalmol 2001; 132:369-377. (C) 2001 by Elsevier Science Inc. All rights reserved.).