Hello DowntoEarth. I also have a mare that is totally blind in her right eye, and is very compromised in the left. Eventually she will be totally blind.
After she went blind in the right eye, I had to be sure to let her know I was there if coming from the right side (still do but its habit now). I did jump her a few times, but she is pretty steady so it wasn't too bad.
As far as riding her, I do not ride on level ground, no arena. So the first time on the trail, it was not great. She kept misjudging the changing level of the ground and was stumbling. Never did that when she had the sight in that eye, so this was very new for us as her depth perception was affected. I was discouraged after that first ride.
But I learned how to prepare her for the change in footing. After that , she is as steady as ever. Either I am cueing her without realizing it, or she has adjusted to the change.
Much will depend on the nature/temperament of your horse as to how well it will adjust to the blindness. My vets have been very encouraging to me because of the trust this mare has for me. Also, she has Walka to help her feel secure in the field. He amazingly has stepped up to the plate and looks out for her. If something startles her, she looks up and tries to locate him. If he is grazing , she puts her head back down and relaxes. Sometimes if she can't see him with her diminished sight, she will call to him. Bless his heart he will give her a little whinny to let her know he's nearby.
Your horse will let you know what is comfortable for him/her. You may need to approach a few things differently either while it is adjusting, or forever. Like trailer loading , I have to move the center bar (I have a two horse straight load) over so she has more room to enter.
Good luck to you and your horse. T and I are enjoying our time together, until she lets me know she's done with trail riding. When she shows that she is scared and unsure, then I will step back and figure out what is best for her at that stage.
Be the kind of woman that when your feet hit the floor each morning the devil says, "Oh crap, she's up!".