Light microscopic analysis of the kitten retina: postnatal development in the area centralis

A method was devised for morphological localization of the area centralis, and the timecourse of its formation as a structural entity was established. Postnatal differentiation of the retina proceeds as follows: the irregularly laminated ganglion cell layer of the newborn becomes unilaminar everywhere but in the presumptive area centralis, a difference which is first discernible at five to six days of age; the outer nuclear layer is always of the same thickness in the area centralis, while in the periphery the layer thins with time; the outer nuclear layer is always thinner in the area centralis than in the periphery; inner nuclear layer thickness is invariant early in postnatal life, but in the adult it is thicker in the area centralis than in the near temporal periphery; plexiform layers form by two weeks of age and rach adult thickness thereafter. Retinal ganglion cells were measured and the percent distributions of three ganglion cell size classes (6-10 micron; 11-20 micron; 21-35 micron) were determined for the area centralis and near temporal periphery; Mean ganglion cell size is constant in center and periphery through five weeks age, is adultlike in the periphery soon thereafter and in the center sometime after eight weeks of age. The percent distribution of ganglion cells by size class in center and periphery is not adultlike even at eight weeks of age. The implications of these observations and others are discussed relative to postnatal growth of the eye and placement of the area centralis in the retinal field and optic axis. The involvement of retinal cell proliferation, cell growth, ganglion cell dendrite formation and cell shape changes in the expansion of the retina are also discussed.