title: Application of adaptive filters to visual testing and treatment in acquired pendular nystagmus.
abstract: Acquired pendular nystagmus (APN) complicates multiple sclerosis and other neurological disorders, causes visual impairment, and frequently resists treatment. Vision could be improved by a visual aid that gates or shifts the seen world in lockstep with the APN. Since the pathological oscillations are embedded in normal eye movements, such a device must track the nystagmus selectively. We evaluated the ability of an adaptive filter to perform this tracking and improve acuity when coupled to either of two devices--a shutter that permitted brief glimpses of the world synchronized with the nystagmus, or simulated image-shifting optics. In 10 normal subjects whose decimal acuity averaged 1.46 +/- 0.20, acuity fell to 0.36 +/- 0.08 under viewing conditions simulating APN. The synchronized shutter restored acuity to 0.60 +/- 0.12, while image-stabilization raised it to 1.17 +/- 0.13. Adaptive filters provide a practical means by which to track nystagmus. The most effective visual aid would couple such filters to image-stabilizing optics.
authors.affiliation: Department of Neurology, Louis Stokes Cleveland Veterans Affairs Medical Center and Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Smith
authors.forename: Brian S
authors.initials: BS
authors.lastname: Oommen
authors.forename: John S
authors.initials: JS
authors.lastname: Stahl
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D000465:Algorithms; D006801:Humans; D016018:Least-Squares Analysis; D007909:Lenses; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000503:physiopathology / Q000534:rehabilitation*; D009991:Oscillometry / Q000295:instrumentation*; D012815:Signal Processing, Computer-Assisted; D014792:Visual Acuity / Q000502:physiology*