Development of the neural retina and its vasculature in the marmoset Callithrix jacchus

The morphological sequence of retinal development in the New World marmoset monkey Callithrix jacchus is similar to previous reports in Macaca and humans. The incipient fovea is present at fetal day (Fd) 100 as the only part of the retina that contains five distinct layers, including a single layer of cone photoreceptors. A foveal pit begins to form at Fd 135 in the center of the foveal avascular zone which is surrounded by a ring of blood vessels (BV) and astrocytes. At birth (Fd 144) the fovea has a single layer of cones over the pit center where the inner retinal layers are thinned but still separated. After birth the fovea rapidly matures so that foveal cone and pit morphology are similar to adult by 4 months. Five distinct layers and the BV plexus in the nerve fiber layer are present to the retinal edge in neonatal marmosets. Near the optic disc BV are sprouting into outer retinal layers at birth and vascularization of the outer retina is completed by 2 to 3 months. Retinal length increases sharply up to Fd 135, but undergoes a quiescent period around birth during which pit formation begins. Length then increases again up to 4mo, followed by a slow increase into adulthood. The postnatal increase is accompanied by a marked thinning of the peripheral retina. The pars plana appears after birth and its length increases at least until 2 years of age. The major difference between marmoset and Macaca is the relative immaturity of the marmoset fovea at birth, and its rapid development after birth. This makes the marmoset a good candidate for neonatal experimental manipulation of retinal and eye development.