Epiretinal pathology of diffuse diabetic macular edema associated with vitreomacular traction

PURPOSE: To investigate the ultrastructure of the vitreomacular interface in patients with diffuse diabetic macular edema (DDME) associated with vitreomacular traction. DESIGN: Laboratory investigation. METHODS: Fifty-five consecutive patients with DDME underwent vitrectomy with en-bloc removal of the inner limiting membrane (ILM) and epimacular tissue. Six patients were operated on both eyes. Sixty-one specimens harvested during vitrectomy were analyzed by electron microscopy. RESULTS: Preoperatively, a thickened premacular cortical vitreous was present in 47 eyes. Native vitreous collagen with single cells interspersed within the collagenous layer or a cellular monolayer were the ultrastructural features in these eyes. Twenty-three eyes showed an epimacular membrane. In eyes with obvious signs of tangential vitreomacular traction, multilayered membranes situated on a layer of native vitreous collagen were found. Fibroblasts and fibrous astrocytes were the predominant cell types; myofibroblasts and macrophages were also present. Sixty of 61 specimens showed native vitreous collagen covering the ILM. Macular edema resolved in 58 eyes and persisted in 3 eyes. No recurrent fibrocellular proliferation was observed during the follow-up period of 18 months (mean, 3 to 56 months). CONCLUSIONS: The vitreomacular interface in eyes with DDME is characterized by a layer of native vitreous collagen and a varying cellular component. Tangential vitreomacular traction is associated with multilayered membranes situated on a layer of vitreous collagen. Resolution of macular edema does not depend on the presence and removal of contractile membranes. In eyes without tangential traction, complete removal of epimacular tissue also leads to fluid resorption.