title: Real-time computer-based visual feedback improves visual acuity in downbeat nystagmus - a pilot study.
abstract: BACKGROUND
  Patients with downbeat nystagmus syndrome suffer from oscillopsia, which leads to an unstable visual perception and therefore impaired visual acuity. The aim of this study was to use real-time computer-based visual feedback to compensate for the destabilizing slow phase eye movements.
  
  
  METHODS
  The patients were sitting in front of a computer screen with the head fixed on a chin rest. The eye movements were recorded by an eye tracking system (EyeSeeCam®). We tested the visual acuity with a fixed Landolt C (static) and during real-time feedback driven condition (dynamic) in gaze straight ahead and (20°) sideward gaze. In the dynamic condition, the Landolt C moved according to the slow phase eye velocity of the downbeat nystagmus. The Shapiro-Wilk test was used to test for normal distribution and one-way ANOVA for comparison.
  
  
  RESULTS
  Ten patients with downbeat nystagmus were included in the study. Median age was 76 years and the median duration of symptoms was 6.3 years (SD +/- 3.1y). The mean slow phase velocity was moderate during gaze straight ahead (1.44°/s, SD +/- 1.18°/s) and increased significantly in sideward gaze (mean left 3.36°/s; right 3.58°/s). In gaze straight ahead, we found no difference between the static and feedback driven condition. In sideward gaze, visual acuity improved in five out of ten subjects during the feedback-driven condition (p = 0.043).
  
  
  CONCLUSIONS
  This study provides proof of concept that non-invasive real-time computer-based visual feedback compensates for the SPV in DBN. Therefore, real-time visual feedback may be a promising aid for patients suffering from oscillopsia and impaired text reading on screen. Recent technological advances in the area of virtual reality displays might soon render this approach feasible in fully mobile settings.
authors.affiliation: Department of Neurology and German Center for Vertigo and Balance Disorders, Ludwig-Maximilans-University Munich, Marchioninistr. 15, 81377, Munich, Germany. julian.teufel@med.uni-muenchen.de.
authors.forename: Julian
authors.initials: J
authors.lastname: Teufel
authors.affiliation: Department of Neurology and German Center for Vertigo and Balance Disorders, Ludwig-Maximilans-University Munich, Marchioninistr. 15, 81377, Munich, Germany. sbardins@nefo.med.uni-muenchen.de.
authors.forename: S
authors.initials: S
authors.lastname: Bardins
authors.affiliation: Division of Internal Medicine, Basel University Hospital, Am Petersgraben 4, 4031, Basel, Switzerland. rainer.spiegel@usb.ch.
authors.forename: Rainer
authors.initials: R
authors.lastname: Spiegel
authors.affiliation: Department of Neurology and German Center for Vertigo and Balance Disorders, Ludwig-Maximilans-University Munich, Marchioninistr. 15, 81377, Munich, Germany. olympia.kremmyda@med.uni-muenchen.de.
authors.forename: O
authors.initials: O
authors.lastname: Kremmyda
authors.affiliation: Institute of Medical Technology, Brandenburg University of Technology Cottbus-Senftenberg, Großenhainer Str. 57, 01968, Senftenberg, Germany. eschneid@hs-lausitz.de.
authors.forename: E
authors.initials: E
authors.lastname: Schneider
authors.affiliation: Department of Neurology and German Center for Vertigo and Balance Disorders, Ludwig-Maximilans-University Munich, Marchioninistr. 15, 81377, Munich, Germany. michael.strupp@med.uni-muenchen.de.
authors.forename: M
authors.initials: M
authors.lastname: Strupp
authors.affiliation: Department of Neurology Inselspital, Bern University Hospital, Freiburgstrasse 4, 3010, Bern, Switzerland. roger.kalla@insel.ch.
authors.forename: R
authors.initials: R
authors.lastname: Kalla
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005133:Eye Movements; D056228:Feedback, Sensory; D005260:Female; D005403:Fixation, Ocular; D006801:Humans; D008297:Male; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000503:physiopathology / Q000628:therapy*; D010775:Photic Stimulation; D010865:Pilot Projects; D011446:Prospective Studies; D011597:Psychomotor Performance; D014792:Visual Acuity