Hi, I have had a hard large pea sized lump behind one ear for around 3 months now. It has not changed size, is not painful and is solid to touch. I have also experienced (I m not sure if the two are related but seemed to occur at the same time) some blurred vision when reading a computer screen in particular. I can look at the screen or a person in front of me and not be able to see parts of the wording.