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Membrana limitans interna and epiretinal membrane lying on macular holes. Some morphological observations
1Zentrum Anatomie, Abteilung Zellbiologie, Medizinische Hochschule Hannover, Germany. reale.enrico@mh-hannover.de
Abstract:
The structure of the membrana limitans interna (MLI) in the region of the macula has been investigated by electron microscopy in (a) 2 enucleated human adult eyes and (b) 38 surgically removed samples associated with an epiretinal membrane (ERM). In the enucleated eye, the glia cells were vitrad bordered either by the lamina rara or, directly, by the lamina densa. Both extended into a coarse network whereby the lamina densa, through repeated branches and anastomoses, delimited large meshes, the lamina rara formed their contents. High magnification revealed that both meshes and contents of this network were composed by a further, finer network. It is suggested that strips and small openings of the finer network are homologous to the cords and intercordal spaces, respectively, which have been indicated as the common, basic structures of most of the basement membranes. The MLI excised with an ERM had the same structure. In some of the ERM associated with a macular hole, myofibroblasts prevailed among the cells. They showed indented nucleus, stress fibers abuting on the plasma membrane or in apparent continuity with bundles of extracellular filaments (microtendons), gap junctions. The cells lay on or were surrounded by a discontinuous basement membrane.
Insights
The internal limiting membrane (ILM) in the macula has a complex, fine network structure. This structure is consistent even when affected by epiretinal membranes (ERM) and macular holes.
Area of Science:
- Ophthalmology
- Cell Biology
- Electron Microscopy
Background:
- The internal limiting membrane (ILM) is the innermost layer of the retina.
- Its detailed structure, particularly in the macula, is crucial for retinal health.
- Epiretinal membranes (ERM) can alter retinal structure and function.
Purpose of the Study:
- To investigate the ultrastructure of the human macular ILM using electron microscopy.
- To compare the ILM structure in healthy eyes versus eyes with epiretinal membranes (ERM).
- To characterize cellular components within ERMs, especially myofibroblasts.
Main Methods:
- Electron microscopy was employed for ultrastructural analysis.
- Samples included 2 enucleated human adult eyes and 38 surgically removed ERM specimens.
- Detailed imaging focused on the ILM and associated cellular and extracellular components.
Main Results:
- The macular ILM exhibits a complex, fine network structure composed of lamina rara and lamina densa.
- This intricate network structure of the ILM was preserved in eyes with ERM.
- In ERM associated with macular holes, myofibroblasts were prevalent, showing characteristic features like stress fibers and discontinuous basement membranes.
Conclusions:
- The internal limiting membrane possesses a consistent, fine, and networked ultrastructure.
- This fundamental structure of the ILM remains largely unchanged even in the presence of epiretinal membranes.
- Myofibroblasts in ERM exhibit specific cellular characteristics indicative of contractile and matrix-producing functions.