A tumor in the pituitary gland can affect your vision. The tumor is probably pressing the eye nerve, so that’s why you are experiencing hemianopia. If the tumor is removed, the chances of recovering your vision are good.
Find a pituitary center at a larger hospital or university. Get copies of everything! You will need testing to know the type of tumor, but usually the larger ones are non-secreting.
If you have a macroadenoma, which is a larger pituitary tumor, then typically the surgery goes through the nose to debulk the tumor and you will likely need radiation after.
You need to search for a very very experienced surgeon for your surgery and don't be afraid to travel. As for the radiation, go to a center who is experienced with radiation in the area, and I would suggest, it it was me, to find proton beam (the newest and most sparring of healthy tissue) or cyber knife (slightly more accurate and more visits, but again, not as sparring as proton beam, but not bad). The oldest type is gamma knife. Most places have it. It is one and done, but it gives you a large dose all at once, and most of my friends ended up with side effects after a while (necrosis and more).
The optic nerve is not very forgiving, so get to the eye doc ASAP, and find a surgeon fast, but get a great one, as they are working close to sensitive areas...