The postnatal development of the optic nerve in hamsters: an electron microscopic study.

The postnatal development of the optic nerve in the golden hamster has been examined using the electron microscope. The number of the optic fibres present in the optic nerve showed an initial increase during the first day after birth but it declined afterwards and tapered off after Day 16. At its peak on postnatal Day 1, there was an average of 314,629 axons in the optic nerve but when the animal reached adulthood only 109,587 fibres remained amounting to about 65% loss of the total fibre population. The period of axon loss coincided with the appearance of large patches of degenerated profiles in the optic nerve. The occurrence of the optic fibre loss has been implied to correlate with the time when the retinal projections were undergoing a dynamic reorganization at the target sites during the process of establishing the adult patterns of retinofugal connections.