glaucoma damage rate?

Can you please explain or give some information on the damage rate of glaucoma over a span of time ?

For eg:- if today my loss is 70% and if i maintain my IOP below 20 or even below 15, how much time will it take for the damage to go to 75%.

i mean i want to know that if i control my IOP how long can i save my eyesight, just a general idea, exact figure not necessary.