There are two different varieties of cataracts, the old age cataracts that you know, but some guinea pigs are also born with the disposition to develop cataracts in early life, sometimes (though rarely) as early as in the womb. So-called congenital cataracts tend to develop typically in the second or third year of the life.
The most difficult period is the transition period while the sight is going but the other senses have not yet compensated. After that, you don't necessarily need to keep things in place anymore, as the piggies will know where what is by smell and touch, and your cataract piggies can perfectly well follow a scent spoor up a ramp, jump on hideys or roam as usual. Free roamers will need time to rebuild a new map of the roaming space with their other senses, but after that, they can live and enjoy life as they have always done.
I have and have had a range of congenital cataract piggies, some of which have especially rehomed because their they would have otherwise been stuck in rescue due to their affliction.
You may find these threads, pictures and videos here reassuring:
https://www.theguineapigforum.co.uk...nd-eye-on-mischief-another-piggy-story.33420/
Mischief also learned to just orientate herself on the lawn by my voice. She could walk herself back in the repositioned run over the distance of several yards just by following my voice commands, as long as I stood next to the entrance flap and kept updating her whether she was still on course ("come on, come on") or whether she was going wrong ("oh,oh,oh"). I would only go and pick her up if she got lost and otherwise challenge her to be as independent as possible.
Here is a video of my 7 year old fully developed cataract girl Mali having blind/old age zoomies:
https://www.facebook.com/pages/Wiebkes-Tribe/250671101630422, first video on the left
My dedicated cataract group free roaming the living room:
Taffy sleeping at the top of the ramp, which we had to make a bit more shallow to suit her. There was not much that escaped her keen hearing and smell!
