I, therefore, got somewhat paranoid that this had change significantly last night when asked to mirror someone on the other side of the set. Not unusual in itself, as we're always watching where each other is out the corner of our eyes to keep lines straight, etc (well, in theory at least). However, when at the end of practice yesterday I was asked this person on the other side of the set, I found that although he could see me, I couldn't see him. It seemed strange at the time, because being further away should have made him easier to see.
So, being utterly paranoid at this time, I argued a bit about where I was aiming to be and didn't admit to not being able to see him, in a most thoroughly unhelpful way.
It was only on the train back that I thought about it and realised that mostly when we're lining up we have people on both sides of us or at some point we turn around and end up on the other side. In the dance in question last night, we were going clockwise around a circle, which would have put him right in the corner of the bad eye that I don't use very much.
I wonder if I'm generally better a lining up with people on my left rather than those on my right? It's not something I've really considered before.
Not exactly helpful for this, but at least it would mean my eyesight is fine, which in all other respect it seems to be. Oh well, guess I'll just have to carry on just trying to know where I should be and aiming for that (and just correct where this is accordingly).