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Logo for the Journal of Rehab R&D
Volume 41 Number 3a, May/June 2004
Pages 313 — 324

Abstract - Application of adaptive filters to visual testing and treatment in acquired pendular nystagmus
Ryan M. Smith, BSEE; Brian S. Oommen, MS; John S. Stahl, MD, PhD
Departments of Neurology, Louis Stokes Cleveland Veterans Affairs Medical Center and Case Western Reserve
University, Cleveland, OH
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.

Key words: adaptive filter; adaptive optics; demyelination; liquid crystal; multiple sclerosis; nystagmus, pathological; optic neuritis; oscillopsia; shutter; visual acuity.

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