In open angle glaucoma 25% nerve damage with effective treatment how long might it take to incur an additional 5-10% nerve damage?

???: Not sure how one can determine 25% optic nerve damage. Technically if you have lost 25% 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.

Unclear: Visual loss due to glaucoma is very patient specific. Each individual needs a certain level of control to avoid ongoing damage. In general, the target pressure is the pressure where glaucoma would not progress. If your pressure has been lowered enough then you should sustain minimal damage going forward. If your pressure is uncontrolled progression will depend how uncontrolled the iop is.