sclera

Etymology

Borrowed from Ancient Greek σκληρός (sklērós, “hard”).

noun

1. (anatomy) The white of the eye; the tough outer coat of the eye that covers the eyeball except for the cornea.
   She'd been back a week and it was clear that college-level track was kicking her ass, the sclera in her normally wide manga-eyes were shot through with blood vessels. 2007, Junot Diaz, The Brief Wondrous Life of Oscar Wao
   Such pressures explain why humans are peculiar in having our rather small irises set against a white background—the sclera—in our eyes. Anyone watching us can infer where we are looking or whom we are looking at. 2016, Joseph Henrich, chapter 13, in The Secret of Our Success[…], Princeton: Princeton University Press