Might a tumor found in between the eye and the brain be removable?

Depends: You probably mean a tumor on the optic nerve or at the base of the brain. These are gliomas - usually not removable without disturbing the sight; meningiomas - frequently removable as they do not invade the nerve and pituitary tumors which are usually removable. There are other rarer ones which sometimes can be removed but might respond to chemo and radio therapy.