This connects the eye to the brain. It has over 1 million nerve fibres in each optic nerve.
Problems with the nerve cause loss of fine vision, colour vision, and field of vision. The nerve may be damaged by eye pressure (glaucoma), inflammation and swelling (optic neuropathy & papillitis), tumours or raised brain pressure (papilloedema).
Swollen nerve (Optic Neuropathy, Papilloedema)