title: Optimizing Chinese character displays improves recognition and reading performance of simulated irregular phosphene maps.
abstract: OBJECTIVE
  A visual prosthesis may elicit an irregular phosphene map relative to a regular electrode array. This study used simulated irregular phosphene maps as a way of optimizing the display methods of Chinese characters (CCs) to improve recognition and reading performance.
  
  
  METHODS
  TWENTY SUBJECTS WITH NORMAL OR CORRECTED SIGHT PARTICIPATED IN TWO EXPERIMENTS (9 FEMALES, 11 MALES, 2030 YEARS OF AGE). EXPERIMENT 1: two character display methods were proposed: selecting phosphenes covered by character strokes on a simulated phosphene array (projection method) and finding the phosphene closest to the expected location in some range of an irregular phosphene array as a substitute (nearest neighbor search [NNS] method). The recognition accuracy of CCs was investigated using six levels for the coverage ratio of stroke and phosphene area and for search range, respectively, for two methods, for several irregularity levels. Experiment 2: reading accuracy (RA) and reading efficiency (RE) were measured using the regular array correspondence and NNS methods.
  
  
  RESULTS
  EXPERIMENT 1: projection and NNS methods were significantly affected by coverage ratio or search range. NNS significantly improved CC recognition accuracy to the highest at 81.3 ± 2.7% and 59.1 ± 5.2%, respectively, for different irregularity levels, compared with the projection method. Experiment 2: RA and RE significantly decreased as the distortion level increased; NNS significantly improved RA (from approximately 40% to >80%) and RE (from approximately 13 char/min to >40 char/min) when reading more irregular paragraphs.
  
  
  CONCLUSIONS
  The performance of CC recognition and paragraph reading when using an irregular phosphene array can be improved through optimizing the display method.
authors.affiliation: School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Yanyu
authors.initials: Y
authors.lastname: Lu
authors.forename: Han
authors.initials: H
authors.lastname: Kan
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Chen
authors.initials: C
authors.lastname: Tao
authors.forename: Yao
authors.initials: Y
authors.lastname: Chen
authors.forename: Qiushi
authors.initials: Q
authors.lastname: Ren
authors.forename: Jie
authors.initials: J
authors.lastname: Hu
authors.forename: Xinyu
authors.initials: X
authors.lastname: Chai
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007803:Language Arts; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010719:Phosphenes / Q000502:physiology*; D011932:Reading; D014792:Visual Acuity / Q000502:physiology; D057488:Visual Prosthesis; D055815:Young Adult