Nystagmus

Collier's New Encyclopedia (1921)

an involuntary movement of the eyeball due to clonic spasm of the muscles of the globe. It usually affects both eyes. The movement is usually horizontal, i. e., from side to side. but it may be rotary. O, o, the 15th letter, and the 4th vowel of the English alphabet. O is called the labial vowel. In English o has six distinct sounds. (1) The sound of o in not, as in pot. (2) The same sound lengthened by a following r, as in or; and in the digraph ou, as in fought, sought. (3) The sound of o in go; and in the digraphs oe, as in foe, toe; oa, as in groan, moan, boat; and ou in though. This sound is modified by r following the vowel, as in more. (4) The sound of o in who, move, tomb; and in the digraphs oo, as in room, soon; and ou, as in through, wound. (5) The sound of u in bull or full, as in wolf, woman. (6) The sound of u in tub, as in son, love, come; and in the digraphs oe, as in does; oo, as in blood; ou, as in enough, tough. O as a symbol is used: As a numeral: As the symbol of nothing, or a cipher. In chemistry for the element oxygen. In old music as the sign of tempus perfectum, or triple time. O, plural OES, an exclamation used in earnest or solemn address, entreaty, appeal, or invocation, and prefixed to the noun of address. O', in Irish proper names, a patronymic prefix corresponding to the Mac of the Highlands of Scotland; thus O'Connell means "the son of Connell."