Help for my aging grandparents

My grandparents are fast approaching 80 years old and have never had proper medical care before two years ago- when they were able to obtain temporary VISAs to visit the United States. They are back in Nigeria now and their situation is desperate! We are raising money towards the legal fees of filing their paperwork, hiring a lawyer and their plane tickets to come to the USA. Only three members (including myself) of my family are in the West, the rest of my family is back in West Africa. My mother partially supports my brother and I while we are pursing out education and supports my grandparents and other members of my family still in West Africa by wiring money. Due to various health issues and random unfortunate situations, my family is already struggling and bringing my grandparents here is very difficult but we cannot leave them the way they are. Right now they are living alone with no one to aid them, they are farmers so they have to work hard to eat and live, their daily chores are way too laborious for young people, let alone someone their age! They have no help or income assistance, they are isolated from the rest of my family and their health is in poor condition. My grandmother can barely walk, frequently has respiratory problems and chronic skin conditions. My grandfather has one eye, in which he is almost completely blind because of a cataract that doctors refuse to risk operating on, he walks with a limp from a severe farm accident (never treated) that happened years ago and he has trouble performing his daily duties. We just want to bring them here so we can be reunited and so that they can live out their later years in peace. Their situation grows more unfavourable as the part of Nigeria in which they are living gets more dangerous because of multiple terrorist attacks and general political uneasiness.