Glaucoma in 1 eye. 30% nerve damage w/"normal" field of vision test reading. how much peripheral would be lost before it affects driving?

Depends: On the location of the loss and how close it is to the center of fixation. Variable effects on driving.

Hard to tell: In most states you only need one eye to drive legally. Before signs of standard visual field damage occurs, 50% of the nerve may be lost. Studies have shown that glaucoma patients with field loss have more accidents and do worse in driving simulations. We do not know what minimum amount of damage is necessary to make driving more difficult. We always try to prevent loss, as much as possible.

? 30%: I would question further into how they are making the assessment if 30% damage and even if you really have glaucoma. You may only be suspect due to a few findings. See an eye md.