Could be a vision problem. I'm near sighted with astigmatism and wear corrective lenses for reading tickets, driving, etc. I notice that when wearing glasses my vision is sharper, but can get slightly distorted near the edges or with quick movement of my head. I don't detect a similar issue with contacts, probably because they're not floating an inch in front of my eyes. The way light and shadow work off of the blade could be skewing his perception.
3/16/15 at 8:41pm