The Japanese public broadcaster, NHK, has mentioned that Ultra HDTV may not be ideal for consumer use (What is Ultra HDTV?).
At close range, the fast moving pictures of an Ultra HD signal on a minimum 60″ screen may cause nausea for it’s viewers.
Recall that Ultra HDTV requires 60 FPS to display images at high-speed. Humans may not be able to process movement at this speed, causing confusion and nausea.