It is never a good plan to let any vision "die away" when it can be saved and assume that the "good eye" will be good all your life. I have scores of patients whee something bad happened to the "good eye" (trauma, disease, ) and it went blind and the "bad" eye is all they have left.
Moreover not doing anything to the bad eye could eventually cause severe pain in the eye that might necessitate removing it from your head.
Get a second opinion from another glaucoma specialist and if they recommend a glaucoma valve surgery suggest you act on that reservation. Most patients with Ahmed Valves don't have any "maintainence"
Thank you For the response. 2 days until surgery. I'm just gonna go for it.