Thanks for replying Ninasmum. Tilly is 10, so would be quite old for PRA, wouldn't she? But it's as well to get her checked out,as you say. I had wondered whether she might have cataract problems. On reflection, she has become a little "clumsy" recently - bashing into cupboards when she turns at speed and generally a bit more anxious. But she also completes her agility circuits with clear rounds and has always been a very confident little dog, which is why this cowering on her walks is so strange. So sorry to hear about Nina - poor little mite, but it sounds as though you are helping her to cope brilliantly. Tilly has never been interested in chasing balls, but I will see if I can get her to do this.
Off to the vets with her then, she will be pleased (not!)
Sue and Tilly