title: Slow cumulative eye position to quantify optokinetic afternystagmus.
abstract: In 30 normal subjects we computed the slow cumulative eye position (SCEP) of optokinetic afternystagmus (OKAN) that followed 60 seconds of full-field optokinetic stimulation at 60 degrees/s. The mean SCEP was 112.8 degrees +/- 65.0 degrees. The lower and upper fifth percentile limits for directional preponderance of the SCEP were -38.8% and 44.3%, respectively. The time constant, which we calculated by dividing the SCEP by the initial velocity, was 12.0 +/- 7.4 seconds. This value is nearly identical to the time constant obtained from semilogarithmic regression of the decay of OKAN slow-phase velocity versus time. We conclude that the SCEP is a good measure of OKAN and that it reflects the substantial amount of variability and directional asymmetry observed in the optokinetic responses of normal subjects.
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: T C
authors.initials: TC
authors.lastname: Hain
authors.forename: G
authors.initials: G
authors.lastname: Patel
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D006801:Humans; D008954:Models, Biological; D009760:Nystagmus, Physiologic / Q000502:physiology*; D009799:Ocular Physiological Phenomena; D011187:Posture / Q000502:physiology; D012016:Reference Values