Hi, what's the difference between a benign cyst and a benign tumor on optic nerve? thanks

Good question, but: Not always a simple answer. Some tumors form cysts. Generally a cyst is trapped fluid in a surrounding layer of non-tumor tissue. "Benign" is a complex term in the nervous system. A tumor cell type can be benign by its growth pattern (doesn't invade or "metastasize") but still a concerning problem because of where it is (on an eye nerve, for example). See ophthalmologist (not optometrist).