Recently diagnosed with glaucoma. no peripheral vision loss. 30% optic nerve damage. with treatment will nerve damage cause loss of vision?

Probably not: Glaucoma is readily treated with anti-pressure medication which should prevent any further damage in almost all cases. This is handled by ophthalmologists (you are not seeing an optometrist i hope?) who deal with this daily. There is a step ladder of treatments -- medication, laser, surgery to prevent further damage which can be quite effective.

Nerve damage already: Done can be stabilized ideally with drops that can lower the eye pressure. If you have no peripheral vision loss on the visual field, then the 30% nerve damage would be surprising. It means that your ophthalmologist did a good job of managing your eye pressure. Make sure that the glaucoma is worked up including ct/mri of the orbits and brain to rule out other causes of optic neuropathy.

???: Not sure how one can determine 30% optic nerve damage. Technically if you have lost 30% of your optic (damage) there is some loss of vision somewhere. Typically this would occur in the periphery first. Today's technology and testing does not check that far out. The goal is to lower the pressure to prevent further optic nerve damage. With treatment one should be able to stop further damage.