ULTRASTRUCTURE OF EPIRETINAL MEMBRANES ASSOCIATED WITH MACULAR HOLES

Background:. The role of tangential traction exerted by epiretinal mem branes in the pathogenesis of macular holes is not fully understood. F urthermore, the role of glial cells in the formation and/or closure of macular holes remains to be elucidated. Methods: To better understand the pathogenesis of macular hole formation and to compare the ultrast ructural features of epiretinal membranes associated with macular hole s of primary and secondary etiology, we harvested 23 translucent epire tinal membranes associated with macular holes stages III-IV at the lim e of pars plana vitrectomy and examined them electron microscopically. Eighteen membranes were obtained from patients with idiopathic macula r holes. 3 membranes from patients with myopic macular holes and 2 epi retinal membranes were associated with macular holes which had develop ed after retinal detachment surgery. Results: Eighteen membranes conta ined a continuous undulating piece of inner limiting lamina (ILL). Six teen of 18 epiretinal membranes at the margins of idiopathic macural h oles, 2 or 3 membranes in myopic macular holes and both membranes asso ciated with a macular hole after retinal detachment surgery demonstrat ed mono- or multilayers of fibrous astrocytes with single macrophage- or fibrocyte-like cells. Vitreous and newly formed collagen occupied t he space between the ILL and the glial cells. Three macular holes were surrounded by rather firmly attached acellular ILL. Conclusion: Glial cells and newly formed collagen may play an important role in macular hole formation by exerting tangential traction regardless of the unde rlying disease process. Glial cells, however, may also be involved in healing of the retinal defect and pars plana vitrectomy with peeling o f an epiretinal membrane, and/or the ILL may induce directed glial cel l proliferation and migration. The similar ultrastructure of epiretina l membranes associated with macular holes and ''simple epiretinal memb ranes'' as described by Foes [8] suggests a common pathogenesis for ma cular holes and macular pucker.