I have a pituitary tumor. I have not had surgery to remove it because I take medication to control it. I am fortunate that my vision has not been affected even though my tumor is fairly large and encasing the carotid artery.
I correspond with many people who also have pituitary tumors, and many who have had the surgery to remove them. Yes, it is very possible that vision will be restored once the pressure from the tumor is off of the optic chiasm. But make sure you get a surgeon who has a lot of experience removing pituitary tumors, you want the very best because the surgery is quite delicate.
If you have any other questions, feel free to ask. Here is a link to the Pituitary Netwark association: http://www.pituitary.org/