Population and proportion of component cells in preretinal membranes.

Cell population and proportion of each component cell type in preretinal membranes formed after retinal detachment were studied by light microscopy (LM) and transmission electron microscopy (TEM). The preretinal membranes were surgically obtained from 20 proliferative vitreoretinopathy (PVR) and 7 macular pucker patients. A thick section from the middle of Epok-embedded specimens stained by toluidine blue was photographed by LM and the area was determined. The cell nuclei were counted on the light micrographs, and the membrane cell population was estimated. All the cells in an ultrathin section of each membrane were photographed by TEM and classified into six types: pigment epithelial cells, astrocytes, macrophages, fibroblasts, cells of other types and unclassified cells. The proportion of these cell types in each membrane was analyzed. There was no significant correlation between the cell populations and duration of retinal detachment or grades of PVR. The proportions of macrophages and pigment epithelial cells were large in early stages of PVR and decreased in late stages, whereas those of astrocytes were the same as those of macrophages or pigment epithelial cells in the early stage and then increased as the duration of retinal detachment became prolonged. These results suggest that macrophages and pigment epithelial cells play important roles in the initiation of preretinal membrane formation in PVR, and that astrocytes participate in the development of rigid membranes. The main component cells in the preretinal membranes obtained from macular pucker patients were astrocytes. The population and the proportion of the astrocytes were almost similar among different stages. These facts suggest that astrocytes play an important role in preretinal membrane formation in macular pucker.