title: Prospects for treating acquired pendular nystagmus with servo-controlled optics.
abstract: OBJECTIVE
  To determine whether a device featuring electronically controlled motor-driven prisms can reduce oscillopsia and improve acuity in patients with acquired pendular nystagmus (APN).
  
  
  METHODS
  A device was developed that senses eye movements and, by the use of motor-driven prisms, oscillates the image of the world in lockstep with the pathologic nystagmus, to negate its deleterious visual effects. Unlike existing optical and surgical treatments for nystagmus, the device negates only the pathologic movements. Voluntary and normal reflex eye movements required for normal vision are unaffected. The benefits of the device were assessed by its impact on acuity in five patients with medication-refractory APN.
  
  
  RESULTS
  All patients reported decreases in oscillopsia when the device was in operation. Averaged across patients, the device increased the percentage of time in which retinal image velocity was within +/-4 degrees/sec from 12.8% to 33.3%. Acuities improved in four of five patients, by an average of 0.21 logMAR units.
  
  
  CONCLUSIONS
  The symptoms of pendular nystagmus can be treated with a servomechanical device. Further refinements in the device should result in greater improvements in acuity, and a portable, wearable version is feasible using existing technologies.
authors.affiliation: Department of Neurology, Case Western Reserve University, Cleveland Veterans Affairs Medical Center, Ohio, USA. jss6@po.cwru.edu
authors.forename: J S
authors.initials: JS
authors.lastname: Stahl
authors.forename: M
authors.initials: M
authors.lastname: Lehmkuhle
authors.forename: K
authors.initials: K
authors.lastname: Wu
authors.forename: B
authors.initials: B
authors.lastname: Burke
authors.forename: D
authors.initials: D
authors.lastname: Saghafi
authors.forename: S
authors.initials: S
authors.lastname: Pesh-Imam
mesh_terms: D000328:Adult; D004581:Electronics; D005133:Eye Movements; D005139:Eyeglasses; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020417:Nystagmus, Congenital / Q000628:therapy*; D055095:Optics and Photonics; D009991:Oscillometry / Q000295:instrumentation*; D014792:Visual Acuity