My optician says the time to do cataracts is when they begin to interfere with your normal life, 'ripe'cataracts is a very old fashioned concept dating to before modern cataract surgery methods.
I had mine done in my early 60s and as I have always been shortssighted and they can put prescription lens in, so that for the first time in 50 years I was able to walk around and cross roads without my glasses on. I now only need glasses for distance seeing (driving,television, reading 'specials' menus onthe walls of cafes).
Cataract surgery was the best thing that ever happened to me, (well nearly).