Glaucoma with 30% optic nerve damage. no peripheral vision loss. for patient to notice peripheral vision loss, how much nerve damage must there be?

Variable: This depends upon the sensitivity of the nerves under the stress of the elevated pressure in the eye. Some will loss measurable amounts of vision at 30% damage, others require more loss to detect it. There is good adaptation so it takes a sensitive person to best detect loss. Best to get treatment and avoid any loss at all.

It depends....: There is no set answer to this. It is generally accepted that to develop a visual field defect about 30% nerve damage may need to occur. The reason that there is no straight answer to this is that it depends on: where the visual field defect occurs since both eyes work together, they compensate and the visual field defect may not be apparent.