Our Jack Russell is around 15 years old and has been getting cataracts as well. We started noticing it a couple years ago. The first time we realized something was up, he went to jump up on the back of my wife's chair. He cleared the top of the chair, bounced off the wall and hit the floor
We noticed he was getting really bad, when I left the house with him snoozing on the back of my recliner. Came home three hours later, he was still on the back of the chair crying. He couldn't figure out how to get back down.
For the most part, he gets around pretty good. Dark and shadows screw with him. He pokes through the house at night, instead of tearing around like he used too. He stays inside when we are gone, and has separate outdoor time from our other dog. We actually keep him separated from our other dog when we aren't at home. He's getting feeble and our other dog senses it and will go after him.
We just roll with it though. He gets hooked to a run if I can't stay outside with him. And make sure he's on the floor when we leave.
Animals are pretty resilient and get around good blind. We used to have a blind horse that could navigate a 10 acre area. Half was pasture, half was woods. If she was in the lower half of the pasture, and you called her, she would come running. Slow down to a walk about 20ft from the barn, and creep in to the stall using your voice as a guide.