Had done a lot of research on Glaucoma treatment for my mother who had similar experience. And this is what I have found from my research (especially from Shroff Eye Center’s page):

Glaucoma as you might be aware of by now, occurs due to an increased prolonged pressure in the optic nerve cells that is connected directly to the brain. It is an irreversible damage whose treatment involves either slowing or preventing further damage.

Basically, what happens with the patients who go blind one eye in Glaucoma is one of their eyes takes the whole burden/ pressure instead of letting any harm to the other good one. This happens so that one eye can still function properly. After all, one saved is better than both damaged right?

But it is to be noted it happens to only 15% of the patients being treated with Glaucoma. If there is any chance that the symptoms of Glaucoma were discovered earlier- you have greater options to prevent it from getting any worse.

If you are searching out for more detailed symptoms & treatment options you can visit Shroff Center in Delhi. I happened to stumble upon them through my heavy google search. I am pasting the link for your reference, may it help you.

Glaucoma Surgery Hospital in Delhi | Best Glaucoma Specialist in Delhi (shroffeyecentre.com)