Ultrastructural findings of epimacular membrane and posterior hyaloid in vitreo-macular traction syndrome

Purpose: Vitreomacular traction syndrome is characterized by an incomplete posterior vitreous detachment and by the cortical vitreous remaining attach ed to the macula. In certain case epimacular membrane is clinically well de fined. We studied the electron microscopic features of epiretinal tissue an d posterior hyaloid removed from the posterior pole. Materiel and Methods: Six epimacular membranes were removed during a pars p lana vitrectomy, placed in 2.5% glutaraldehyde solution, embedded in Epoxy resin, and examined in a transmission electron microscope. The detached pos terior hyaloid was removed and analyzed separately in two cases. Results: The analysis disclosed five morphologically cell types. Fibrous as trocytes were predominant in five cases. Other cell types were less frequen t and were identified as fibroblasts, macrophages and myofibroblasts. In on e case epithelial-like cell type was predominant. The stroma was mainly com posed of a thin layer of 15-nm diameter collagen evoking a vitreous origin. Internal limiting membrane was present in one case only. Detached posterio r hyaloid was constituted by the same cellular constituents on thin layer o f vitreous collagen. Discussion: The cellular proliferation is principally constituted by fibrou s astrocyte and occurs on the inner surface of cortical vitreous. Some glia l cells seem to present an epithelial differentiation. Conclusion: The attached and detached posterior hyaloid in vitreomacular tr action syndrome is the place of glial cells migration and proliferation.