title: Testing of semichronically implanted retinal prosthesis by suprachoroidal-transretinal stimulation in patients with retinitis pigmentosa.
abstract: OBJECTIVE
  To examine the safety and effectiveness of a retinal prosthesis that is implanted semichronically in two patients with advanced retinitis pigmentosa (RP).
  
  
  METHODS
  Two eyes of two patients with advanced RP had a retinal prosthesis implanted in a sclera pocket of one eye. The visual acuity of both eyes before the implantation was bare light perception. Phosphenes were elicited by suprachoroidal-transretinal stimulation (STS). The internal devices of the STS were implanted under the skin on the temporal side of the head, and the 49 electrode-array was implanted in the scleral pocket of one eye. Biphasic electrical pulses (duration, 0.5 ms; frequency, 20 Hz) were delivered through nine active electrodes. The threshold current was determined by currents ≤1 mA. Behavioral tasks were used to determine the functioning of the prosthesis.
  
  
  RESULTS
  The surgery was completed without a retinal detachment and retinal/vitreous hemorrhage. The implanted STS system remained functional for the 4-week test period. Phosphenes were elicited by currents delivered through six electrodes in Patient 1 and through four electrodes in Patient 2. The success of discriminating two bars was better than the chance level in both patients. In Patient 2, the success of a grasping task was better than the chance level, and the success rate of identifying a white bar on a touch panel increased with repeated testing.
  
  
  CONCLUSIONS
  Semichronic implantation of a microelectrode-STS system showed that it was safe and remained functional for at least 4 weeks in two patients with advanced RP. (www.umin.ac.jp/ctr number, R000002690.).
authors: Department of Applied Visual Science, Osaka University Graduate School of Medicine, Osaka, Japan. fujikado@ophthal.med.osaka-u.ac.jp
authors: Takashi
authors: T
authors: Fujikado
authors: Motohiro
authors: M
authors: Kamei
authors: Hirokazu
authors: H
authors: Sakaguchi
authors: Hiroyuki
authors: H
authors: Kanda
authors: Takeshi
authors: T
authors: Morimoto
authors: Yasushi
authors: Y
authors: Ikuno
authors: Kentaro
authors: K
authors: Nishida
authors: Haruhiko
authors: H
authors: Kishima
authors: Tomoyuki
authors: T
authors: Maruo
authors: Kunihiko
authors: K
authors: Konoma
authors: Motoki
authors: M
authors: Ozawa
authors: Kohji
authors: K
authors: Nishida
mesh_terms: D000368:Aged; D002829:Choroid; D004558:Electric Stimulation / Q000295:instrumentation*; D004567:Electrodes, Implanted; D004867:Equipment Design; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D008839:Microelectrodes; D020127:Recovery of Function; D012160:Retina / Q000502:physiology*; D012174:Retinitis Pigmentosa / Q000503:physiopathology / Q000601:surgery*; D014792:Visual Acuity; D057488:Visual Prosthesis