There is a way to check very quickly without a vet.
Bring your horse into a dark area and have a little pen light or a small flashlight ready. Shine the light into the horse's eye. If they are working right, the pupils will contract in responce to the light.
I knew someone who noticed the pupil on her horse never changed or contracted so she contacted the vet. They discovered he was blind in that eye even though there was no clouding. He was still jumping though.
I've done this to a couple massage therapy clients when they asked me why their horse was refusing at jumps. I checked their eyes real fast and (after stating I wasn't a vet), it appeared that the horse could see properly, so it was probably a training or pain issue. Its always good to rule out sight issues though. Eyes can be damaged easily and the damage can happen and spread quickly, so if you have any concerns over the eyes, you need to have a vet look at it to see treatment.
If the horse is bumping you into the wall, you need more outside leg.
And those who were seen dancing were thought to be insane by those who could not hear the music