The sub-clinical see-saw nystagmus embedded in infantile nystagmus.

Full Abstract

A transient, decompensated vertical phoria in an individual with infantile nystagmus syndrome (INS) resulted in two images that oscillated vertically-a diplopic oscillopsia. Ocular motor studies during the vertical oscillopsia recreated by vertical prisms, led to the identification of a sub-clinical see-saw nystagmus (SSN), present under the prism-induced diplopic condition. Retrospective analysis of ocular motor recordings made prior to the above episode of vertical diplopia revealed the presence of that same sub-clinical SSN. The SSN had not been detected previously despite extensive observations and recordings of this subject's pendular IN over a period of forty years. Three- dimensional search-coil data from fourteen additional INS subjects (with pendular and jerk waveforms) confirmed the existence of sub-clinical SSN embedded within the clinically detectable horizontal-torsional IN in seven of the fifteen and a sub-clinical, conjugate, vertical component in the remaining eight. Unlike the clinically visible SSN found in achiasma, the cause of this sub-clinical SSN is hypothesized to be due to a failure of the forces of the oblique muscles (responsible for the torsional component of the IN) to balance out the associated forces of the vertical recti; the net result is a small, sub-clinical SSN. Thus, so-called "horizontal" IN is actually a horizontal-torsional oscillation with a secondary, sub-clinical SSN or conjugate vertical component. The suppression of oscillopsia by efference copy in INS appears to be accomplished for each eye individually, even in a binocular individual. However, failure to fuse the two images results in oscillopsia of one of them.

Author information

Author/s: Dell'Osso, L F (LF); Jacobs, J B (JB); Serra, A (A);

Affiliation: Daroff-Dell'Osso Ocular Motility Laboratory, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, CASE Medical School, 10701 East Boulevard, Cleveland, OH 44106, USA. lfd(-atsign-)case.edu

Journal and publication information

Publication Type: Journal Article; Research Support, U.S. Gov't, Non-P.H.S.

Journal: Vision research (Vision Res), published in England. (Language: eng)

Reference: 2007-Feb; vol 47 (issue 3) : pp 393-401

Dates: Created 2007/01/23; Completed 2007/03/29; Revised 2007/11/15;

PMID: 17045326, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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