I'm not so sure that Piper can see very well (or at all?) out of her left eye. I've noticed just recently that it reflects light very differently than her right. There's a yellow hue that fills that eye, while the other stays dark. It reminds me a lot of Odin's eyes (my blind foster.) I tried to do some tests, holding one hand over each eye and having her follow a toy, and she was definitely stronger on her right.
I just went back and studied old pictures, and the different eyes seemed to start after we moved. She's due for her annual, so I'll have the vet check it out.
There is a condition called Retinal Dysplasia in dogs, and it occurs frequently with labs. There is no treatment. The site I looked at said that it can mean minor vision impairments to blindness.
It doesn't scare me that she may be blind in one eye. It certainly hasn't slowed her down, and I'm not worried about it, I just thought I'd share.