Hi Ginger. A field test is where they are able to get a complete mapping of your peripheral vision. Glaucoma is loosing that part of your vision and can lead to blindness. Maybe if you just call your doc and ask if they have performed that test. There are probably other things that cause one to lose the peripheral vision.
I truly feel for you in sewing, especially threading needles. Feel free to pm me if you would like to. Linda :-D