Ganglion cells form the ganglion cell layer (stratum ganglionare). They send their axons into the marginal zone and along the basement membrane towards the retinal fissure. With the increase in the number of axons, the optic fiber layer (stratum neurofibrarum) arises between the ganglion cells and the limiting membrane of the retina (membrana limitans interna). Maturation of dendrites and axons of ganglion cells, amacrine cells and bipolar cells leads to the formation of a neuropil. This forms the inner plexiform layer (stratum plexiforme internum), which separates the layer of ganglion cells from the cell layer situated more distally. This cell layer becomes the internal nuclear layer (stratum nucleare internum).
The remaining ventricular zone will give rise to photoreceptors, horizontal cells and bipolar cells, as well as some Müller cells. The outer plexiform layer (stratum plexiforme externum) arises later. It separates the perikarya of the photoreceptors (external nuclear layer, stratum nucleare externum) from the cells located in the internal granular layer (horizontal, bipolar, amacrine, and Müller cells).
Formation of the retinal layers follows a gradient of maturation from the centre towards the periphery. At the ora serrata, the photosensitive pars optica retinae continues into the blind pars caeca, which consists of a bistratified epithelium without photoreceptors. This pars caeca covers the ciliary body as the ciliary part of the retina, and covers the posterior aspect of the iris as the iridal part of the retina.