Overview
The optic nerve begins at the optic disc – a structure visible on ocular examination. The optic disc varies in size between people, ranging from 1.2 to 2.5mm in diameter. The implications of disc size on glaucoma diagnosis will be discussed later in this atlas.
The nerve fibres that make up the optic nerve originate from the photoreceptors in the retina. Information from the photoreceptors is transmitted by bipolar and amacrine cells to the retinal ganglion cells. From here, the information is taken via the retinal ganglion cell axons to the optic nerve which is responsible for carrying approximately 1.2 million nerve fibres towards the optic chiasm. At the chiasm, approximately half the nerve fibres decussate before heading back to the lateral geniculate nucleus and on to the visual cortex.
This chapter will look at both congenital and acquired conditions of the optic nerve. An in-depth discussion of glaucoma will be released in late 2021 as we continue to expand this resource, however for now it is covered in brief on the tab below.