My wife has pain in the back of her head to neck and ear. sometimes the pain is very huge that she has to take painkillers. she's been with this pain for days now. she is completely blind after retina detechment years ago. whats the cause of this?

I can think of no way a retinal detachment and headache can be associated except maybe an auto accident that detached retina and injured neck. Quiz her about this possibility.

She likely needs and eye exam and an MRI. Worsening HA requiring medications requires an evaluation. She definitely at a minimum should see an eye doctor and possibly a retina specialist.