Ultrastructural analysis of the optic nerve in microphthalmic rodents (Spalax leucodon)

: The optic nerve of a microphthalmic subterranean rodent, Spalax leucodon, has been examined at the ultrastructural level. The analysis of the optic nerve reveals only 1,790 unmyelinated axons. The axon diameter varies from 0.05 to 2.3 microns, with a mean of 0.55 micron. We suggest that these axons mainly belong to the W type ganglion cells.