Definition of "monocular"

...one of his sparks alighted upon my eye and destroyed it making me a monocular ape;

1885–1888, Richard F[rancis] Burton, transl. and editor, A Plain and Literal Translation of the Arabian Nights’ Entertainments, now Entituled The Book of the Thousand Nights and a Night […], Shammar edition, volume (please specify the volume), [London]: […] Burton Club […]

You are not such a foolish woman as to like to be seen with Fred Mostyn, that little monocular snob, after the aristocratic, handsome Basil Stanhope.

1906, Amelia Barr, The Man Between

The moony monocular set in his eye / Appeared to be scanning the Sweet Bye-and-Bye.

1911, Ambrose Bierce, “lord”, in The Devil’s Dictionary, New York, N.Y., Washington, D.C.: The Neale Publishing Company

Monoculars are designed to fit discreetly in the hand, improving their cosmetic appearance. Most monoculars sold today have one primary optical difference from binoculars: the ability to focus at close range. These are known as short-focus telescopes.

2010, Duane R. Geruschat, Audrey J. Smith, “Low Vision for Orientation and Mobility”, in Foundations of Orientation and Mobility, 3rd edition, volumes 1: History and Theory, New York: American Foundation for the Blind, page 75