Electron immunocytochemical analysis of posterior hyaloid associated with diabetic macular edema

Background: Tangential traction in the macula from a thickened posterior hyaloid of the vitreous has been implicated as a cause of diffuse diabetic macular edema. Vitrectomy with peeling of the posterior hyaloid has been shown to reduce retinovascular leakage and improve vision in select patients. We report a clinicopathologic correlation using electron microscopy and electron immunocytochemistry to characterize the membrane infiltrating the posterior hyaloid in two such patients. Methods: Two patients presented with vision loss associated with diffuse diabetic macular edema and an attached thickened, and taut posterior hyaloid. The patients underwent vitrectomy with peeling of the posterior hyaloid. The premacular posterior hyaloid specimens then were analyzed by electron microscopy with immunocytochemical staining for cytokeratin and glial fibrillary acidic protein. Results: Both posterior hyaloid specimens contained collagen and a large cellular component. Immunogold labeling showed cells positive for glial fibrillary acidic protein or cytokeratin. With double labeling, no cells expressed both proteins simultaneously. Clinically, both patients had vision improvement and macular edema resolution after surgery. Conclusions: The thickened, taut posterior hyaloid observed in our patients with diabetic macular edema contained cells of glial and epithelial origin. This cellular infiltration may contribute to abnormal vitreomacular adherence and could play a role in the pathogenesis of macular edema in some patients with diabetes.