Marijuana contains cannabinoids ( a group of sixty chemicals) in a single puff of joint. Marijuana is basically weed, grass, herb, or bud etc which is basically dried leaves, seeds or stems of the plant Cannabis indica plant or Cannabis sativa. It is one of the most used drugs in the world. It is mood altering in nature.
Optic nerve, also known as the second cranial nerve, is located at the back of the eye. The small photoreceptor cells in the brain sense the light and transmit impulses to the optic nerve which then carries the impulses to the brain where the visual information gets interpreted.