Welcome to Neuro talk, anytime..... I am sorry to hear of your mothers trouble with PN and with her eyes. I take it that your mother doesn't have insurance for medications? I was in this spot myself before I received disability. Write to the company who produces the medication. Often there is a program to pay for the medications. Your doctor may have to write a note of "need" This worked for me with several medications I needed but could not afford.
I also understand about your moms pain. If possible please seek out a pain specialist. There is help there if you will seek it out. Living in pain like that is hard on the person, and very hard on the family to watch it happen. If money is an issue, call the hot line for referrals to doctors who treat, and will see a person on a sliding scale. Pain can be controlled, and there can be a good quality of life if you seek the proper medical care. I really think you are wonderful for trying to help your mom. Your primary care specialist for your mother may be the best place to start to try and find a good pain specialist. There are medications that do not interfer with glaucoma. I do wish you all th best with your family. ginnie