title: Towards an assistive peripheral visual prosthesis for long-term treatment of retinitis pigmentosa: evaluating mobility performance in immersive simulations.
abstract: OBJECTIVE
  The prospective efficacy of a future peripheral retinal prosthesis complementing residual vision to raise mobility performance in non-end stage retinitis pigmentosa (RP) was evaluated using simulated prosthetic vision (SPV).
  
  
  METHODS
  Normally sighted volunteers were fitted with a wide-angle head-mounted display and carried out mobility tasks in photorealistic virtual pedestrian scenarios. Circumvention of low-lying obstacles, path following, and navigating around static and moving pedestrians were performed either with central simulated residual vision of 10° alone or enhanced by assistive SPV in the lower and lateral peripheral visual field (VF). Three layouts of assistive vision corresponding to hypothetical electrode array layouts were compared, emphasizing higher visual acuity, a wider visual angle, or eccentricity-dependent acuity across an intermediate angle. Movement speed, task time, distance walked and collisions with the environment were analysed as performance measures.
  
  
  RESULTS
  Circumvention of low-lying obstacles was improved with all tested configurations of assistive SPV. Higher-acuity assistive vision allowed for greatest improvement in walking speeds-14% above that of plain residual vision, while only wide-angle and eccentricity-dependent vision significantly reduced the number of collisions-both by 21%. Navigating around pedestrians, there were significant reductions in collisions with static pedestrians by 33% and task time by 7.7% with the higher-acuity layout. Following a path, higher-acuity assistive vision increased walking speed by 9%, and decreased collisions with stationary cars by 18%.
  
  
  CONCLUSIONS
  The ability of assistive peripheral prosthetic vision to improve mobility performance in persons with constricted VFs has been demonstrated. In a prospective peripheral visual prosthesis, electrode array designs need to be carefully tailored to the scope of tasks in which a device aims to assist. We posit that maximum benefit might come from application alongside existing visual aids, to further raise life quality of persons living through the prolonged early stages of RP.
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: Paul B
authors.initials: PB
authors.lastname: Matteucci
authors.forename: Nigel H
authors.initials: NH
authors.lastname: Lovell
authors.forename: Gregg J
authors.initials: GJ
authors.lastname: Suaning
mesh_terms: D017076:Computer-Aided Design; D004599:Electric Stimulation Therapy / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D051346:Mobility Limitation; D058117:Neural Prostheses; D016544:Patient Simulation; D011474:Prosthesis Design / Q000379:methods; D012174:Retinitis Pigmentosa / Q000150:complications / Q000175:diagnosis / Q000534:rehabilitation*; D012656:Self-Help Devices; D013647:Task Performance and Analysis; D016896:Treatment Outcome; D014584:User-Computer Interface; D014786:Vision Disorders / Q000175:diagnosis / Q000209:etiology / Q000534:rehabilitation*; D057488:Visual Prosthesis; D055815:Young Adult