This is the optic nerve of a young man. The optic nerve is normally orangish and round. But you can see there’s some white material just below this optic nerve (it’s actually above since the image is reversed in the photo). You can see the retina blood vessels overlying the white material. This material is “myelination”. Myelin is the insulation of the nerves in our bodies. When the optic nerve enters the eye, the nerve fibers lose their insulation. But in this case you see a little of the myelin coming into the retina a little. This does not cause any harm at all in thsi small extent.