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				There are rumours that Túrin wore glasses. He lost them at Nargothrond, and ended up not knowing that Níniel and Nienor look waaay too alike.
			
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 I can imagine him saying, "You know, your hair kinda blurs like somebody else I know...." 
 
I have a hunch that Saruman provided the Uruk-Hai with sunscreen and UV-resistant contact lenses, giving them the ability to appear during daylight.