Patterns of cell death in the ganglion cell layer of the human fetal retina.

The distribution of dying cells in the ganglion cell layer (GCL) of retinae from human fetuses has been analysed. Both whole-mounted and sectioned retinae have been studied. Results suggest that cells are lost from the GCL between weeks 14 and 30 of the gestation period, approximately. This period corresponds to the period during which axons are lost from the developing optic nerve. Cell loss is greatest between weeks 16 and 21 of the gestation period. The pattern of cell loss is nonuniform, and between weeks 16 and 24, the relative frequency of pyknotic cells (pyknotic cells:viable cells) in peripheral retina is considerably higher than in central retina. This pattern of cell loss predominates during the period in which a distinct centroperipheral gradient of cell densities emerges in the GCL of the human fetal retina (between 18 and 23 weeks gestation). It is suggested that the regional loss of ganglion cells may contribute to the formation of the cell density gradient.