The influence of visual field position induced by a retinal prosthesis simulator on mobility

  • Takao Endo
  • Kenta Hozumi
  • Masakazu Hirota
  • Hiroyuki Kanda
  • Takeshi Morimoto
  • Kohji Nishida
  • Takashi FujikadoEmail author
Low Vision



Our aim is to develop a new generation of suprachoroidal–transretinal stimulation (STS) retinal prosthesis using a dual-stimulating electrode array to enlarge the visual field. In the present study, we aimed to examine how position and size of the visual field—created by a retinal prosthesis simulator—influenced mobility.


Twelve healthy subjects wore retinal prosthesis simulators. Images captured by a web camera attached to a head-mounted display (HMD) were processed by a computer and displayed on the HMD. Three types of artificial visual fields—designed to imitate phosphenes—obtained by a single (5 × 5 electrodes; visual angle, 15°) or dual (5 × 5 electrodes ×2; visual angle, 30°) electrode array were created. Visual field (VF)1 is an inferior visual field, which corresponds to a dual-electrode array implanted in the superior hemisphere. VF2 is a superior visual field, which corresponds to a single-electrode array implanted in the inferior hemisphere. VF3 is a superior visual field, which corresponds to a dual-electrode array implanted in the inferior hemisphere. In each type of artificial visual field, a natural circular visual field (visual angle, 5°) which imitated the vision of patients with advanced retinitis pigmentosa existed at the center. Subjects were instructed to walk along a black carpet (6 m long × 2.2 m wide) without stepping on attached white circular obstacles. Each obstacle was 20 cm in diameter, and obstacles were installed at 40-cm intervals. We measured the number of footsteps on the obstacles, the time taken to complete the obstacle course, and the extent of head movement to scan the area (head-scanning). We then compared the results recorded from these 3 types of artificial visual field.


The number of footsteps on obstacles was lowest in VF3 (One-way ANOVA; P = 0.028, Fisher’s LSD; VF 1 versus 3 P = 0.039, 2 versus 3 P = 0.012). No significant difference was observed for the time to complete the obstacle course or the extent of head movement between the 3 visual fields.


The superior and wide visual field (VF3) obtained by the retinal prosthesis simulator resulted in better mobility performance than the other visual fields.


Mobility test Suprachoroidal–transretinal stimulation Retinal prosthesis simulator Visual field Head-scanning 



This study was supported by KAKENHI (Grants-in-Aid for Scientific Research B 16H05487).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the Ethics Committee of Osaka University Hospital and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Takao Endo
    • 1
  • Kenta Hozumi
    • 1
  • Masakazu Hirota
    • 2
  • Hiroyuki Kanda
    • 2
  • Takeshi Morimoto
    • 2
  • Kohji Nishida
    • 1
  • Takashi Fujikado
    • 2
    Email author
  1. 1.Department of OphthalmologyOsaka University Graduate School of MedicineOsakaJapan
  2. 2.Department of Applied Visual ScienceOsaka University Graduate School of MedicineOsakaJapan

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