title: Assistive peripheral phosphene arrays deliver advantages in obstacle avoidance in simulated end-stage retinitis pigmentosa: a virtual-reality study.
abstract: OBJECTIVE
  The prospective efficacy of peripheral retinal prostheses for guiding orientation and mobility in the absence of residual vision, as compared to an implant for the central visual field (VF), was evaluated using simulated prosthetic vision (SPV).
  
  
  METHODS
  Sighted volunteers wearing a head-mounted display performed an obstacle circumvention task under SPV. Mobility and orientation performance with three layouts of prosthetic vision were compared: peripheral prosthetic vision of higher visual acuity (VA) but limited VF, of wider VF but limited VA, as well as centrally restricted prosthetic vision. Learning curves using these layouts were compared fitting an exponential model to the mobility and orientation measures.
  
  
  RESULTS
  Using peripheral layouts, performance was superior to the central layout. Walking speed with both higher-acuity and wider-angle layouts was 5.6% higher, and mobility errors reduced by 46.4% and 48.6%, respectively, as compared to the central layout. The wider-angle layout yielded the least number of collisions, 63% less than the higher-acuity and 73% less than the central layout. Using peripheral layouts, the number of visual-scanning related head movements was 54.3% (higher-acuity) and 60.7% (wider-angle) lower, as compared to the central layout, and the ratio of time standing versus time walking was 51.9% and 61.5% lower, respectively. Learning curves did not differ between layouts, except for time standing versus time walking, where both peripheral layouts achieved significantly lower asymptotic values compared to the central layout.
  
  
  CONCLUSIONS
  Beyond complementing residual vision for an improved performance, peripheral prosthetic vision can effectively guide mobility in the later stages of retinitis pigmentosa (RP) without residual vision. Further, the temporal dynamics of learning peripheral and central prosthetic vision are similar. Therefore, development of a peripheral retinal prosthesis and early implantation to alleviate VF constriction in RP should be considered to extend the target group and the time of benefit for potential retinal prosthesis implantees.
authors.affiliation: Graduate School of Biomedical Engineering, UNSW Australia, Sydney 2052, Australia.
authors.forename: Marc Patrick H
authors.initials: MP
authors.lastname: Zapf
authors.forename: Mei-Ying
authors.initials: MY
authors.lastname: Boon
authors.forename: Nigel H
authors.initials: NH
authors.lastname: Lovell
authors.forename: Gregg J
authors.initials: GJ
authors.lastname: Suaning
mesh_terms: D005260:Female; D006801:Humans; D049449:Luminescence; D008297:Male; D010719:Phosphenes; D012174:Retinitis Pigmentosa / Q000503:physiopathology / Q000523:psychology / Q000628:therapy*; D018910:Video Games / Q000523:psychology; D063367:Virtual Reality Exposure Therapy / Q000379:methods*; D057488:Visual Prosthesis; D055815:Young Adult