title: [Ocular electrical stimulation: Therapeutic application and active retinal implants for hereditary retinal degenerations].
abstract: BACKGROUND
  Electrical stimulation has a long history in ophthalmology. Subthreshold electrical stimulation can have beneficial therapeutic effects on hereditary degenerative retinal diseases. Suprathreshold stimulation is able to elicit visual perceptions and, if multielectrode fields are arranged as an array, usable pictures can be perceived by blind patients.
  
  
  OBJECTIVE
  This is a review article on the current situation and studies on therapeutic transcorneal electrical stimulation. Moreover, the challenges, surgical concepts and visual results of active retinal implants are discussed.
  
  
  METHODS
  This article gives an overview on transcorneal electrical stimulation and active retinal implants based on published results, with special emphasis on the clinical application.
  
  
  RESULTS
  The results of initial controlled studies on therapeutic transcorneal electrical stimulation in hereditary retinal diseases were very promising. The largest controlled study so far in patients with retinitis pigmentosa (RP) has yielded many positive trends and some significant improvements in electrophysiological data. Currently, two retinal implants have regulatory approval, the Argus II retinal prosthesis system® (SecondSight®) and the Alpha-IMS© (Retina Implant AG). Both systems can be used to improve visual perception and under test conditions can achieve visual acuities of 0.02 and 0.04, respectively.
  
  
  CONCLUSIONS
  In-depth analyses and follow-up studies in larger patient groups are currently planned to definitively clarify the potential of therapeutic transcorneal electrical stimulation in RP patients. The challenges of currently available active retinal implants are the technical biostability and the limited spatial resolution.
authors: Augenklinik am Katharinenhospital, Klinikum Stuttgart, Kriegsbergstraße 60, 70174, Stuttgart, Deutschland. f.gekeler@klinikum-stuttgart.de.|Department für Augenheilkunde, Eberhard-Karls-Universität Tübingen, Tübingen, Deutschland. f.gekeler@klinikum-stuttgart.de.
authors: F
authors: F
authors: Gekeler
authors: Department für Augenheilkunde, Eberhard-Karls-Universität Tübingen, Tübingen, Deutschland.
authors: E
authors: E
authors: Zrenner
authors: Department für Augenheilkunde, Eberhard-Karls-Universität Tübingen, Tübingen, Deutschland.
authors: K U
authors: KU
authors: Bartz-Schmidt
mesh_terms: D004599:Electric Stimulation Therapy / Q000295:instrumentation* / Q000379:methods; D019544:Equipment Failure Analysis; D019317:Evidence-Based Medicine; D006801:Humans; D011474:Prosthesis Design; D012162:Retinal Degeneration / Q000151:congenital* / Q000175:diagnosis / Q000628:therapy*; D016896:Treatment Outcome; D014786:Vision Disorders / Q000151:congenital* / Q000175:diagnosis / Q000517:prevention & control*; D014792:Visual Acuity; D057488:Visual Prosthesis
keywords: Electrostimulation; Implant; Retina; Retinitis pigmentosa; Transcorneal electrical stimulation