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."
What Has Changed in the Last Century
Collier's in 1921 called nystagmus a "clonic spasm of the muscles of the globe" — locating the fault in the eye muscles themselves. Modern ophthalmology places it in the brain's gaze-holding machinery instead: the neural integrator and vestibular pathways that should keep the eyes still, with distinct forms now separated out (infantile, vestibular, downbeat, upbeat, see-saw), each pointing to a different lesion. One cause common in 1921 has all but vanished: miner's nystagmus, blamed on years of work in dim lamplight and a compensable industrial disease in Britain, disappeared as pits got electric lighting. There are now drug treatments where before there were none — gabapentin and memantine for acquired nystagmus, 4-aminopyridine for the downbeat form — and genes such as FRMD7 have been tied to inherited infantile nystagmus.
Written for this edition, 2026.