A light microscopic study of the developing human neural retina.

Human embryonic and fetal eyes from 4 mm to 200 mm crown-rump length (26 days to 21 weeks of gestation) were studied in 0.75-micron sections impregnated with silver and toned with gold. The layer of Chievitz was formed by an inward migration of ganglion-cell and Müller-cell nuclei from the outer neuroepithelium and then, after further changes in nuclear location, the layer of Chievitz was cleared of ganglion-cell nuclei to become the definitive inner plexiform layer. Müller-cell nuclei later populated all retinal layers in the fetus. The argyrophilic Müller-cell cytoplasm associated with neuronal development is discussed in relation to glia-neuron interactions, with emphasis on the particular needs of retinal tissue.