if you are aware of structure of eye then dr mittal's answer will satisfy you otherwise you will have to study and understand the structure and function of eye 1st.

Hello These two are entirely different A.  Vitreous hemorrhage is bleeding in retina where blood gets mixed with vitreous of eye. Bleeding could be due to many causes like diabetes, Inflammation of eye etc B.  Optic nerve swelling... Is swelling of Optic nerve (nerve which connects brain to brain). Swelling mat appear due to many causes like optic neuritis, papilloedema etc