As your described, it's a vision loss in a few parts of the visual field with one eye, you also have a balance problem, it means you do need a MRI or CAT scan on the head.
Sudden loss of vision has three general causes:
Clouding of normally transparent eye structures
Abnormalities of the retina (the light-sensing structure at the back of the eye)
Abnormalities of the nerves that carry visual signals from the eye to the brain (the optic nerve and the visual pathways)
What can cause a balance problem include:
inner ear problem
You have both imbalance and vision problem, a head problem is the first to rule out.