sightedness

näkö The quality of being sighted, or having the ability to see.
1995, James Lester, Too Marvelous for Words: The Life and Genius of Art Tatum (page 65)

Bill said that he learned to be tactful — if Art asked where something was, a telephone for example, Bill would feign not knowing himself, so as not to emphasize his sightedness, then appear to find out and tell him.