title: Positioning of electronic subretinal implants in blind retinitis pigmentosa patients through multimodal assessment of retinal structures.
abstract: OBJECTIVE
  To optimize methods for positioning subretinal visual implants, customizing their cable length, guiding them to the predetermined retinal position, and evaluating their performance.
  
  
  METHODS
  Ten eyes of 10 patients (6 male, 4 female, mean age 46.4 years) were investigated before implantation of a subretinal visual implant. The structural characteristics of the retina as well as the ocular dimensions were determined. Topographic images of the prospective implantation site were subdivided into grids of squares. Each square received a weighted score for suitability. The sum of the scores was calculated, and the region with the highest score was chosen for the implant. In each case, the implant's power supply cable length was calculated by means of magnetic resonance imaging. The planned and achieved positions before and after implantation were compared.
  
  
  RESULTS
  The mean light sensitivity ratio between the area actually covered by the chip and that of the planned position was 90.8% with an SD of 11.4%. In two cases with almost perfect positioning, the computed ratio was 100%. Measurements showed that to achieve a 95% sensitivity rate the difference between the planned and achieved chip position must be less than 1.7 mm. Preoperative calculations of the intraocular cable length proved accurate in all cases.
  
  
  CONCLUSIONS
  Preoperative evaluation of retinal structures and eye morphology is useful for guiding a retinal implant to the designated area. It is a meaningful tool for planning and performing retinal chip implantation, and it optimizes personalized implantation. (ClinicalTrials.gov numbers, NCT00515814, NCT01024803.).
authors.affiliation: University of Tübingen, Centre for Ophthalmology, Tübingen, Germany. kusnyerik.akos@med.semmelweis-univ.hu
authors.forename: Akos
authors.initials: A
authors.lastname: Kusnyerik
authors.forename: Udo
authors.initials: U
authors.lastname: Greppmaier
authors.forename: Robert
authors.initials: R
authors.lastname: Wilke
authors.forename: Florian
authors.initials: F
authors.lastname: Gekeler
authors.forename: Barbara
authors.initials: B
authors.lastname: Wilhelm
authors.forename: Helmut G
authors.initials: HG
authors.lastname: Sachs
authors.forename: Karl Ulrich
authors.initials: KU
authors.lastname: Bartz-Schmidt
authors.forename: Uwe
authors.initials: U
authors.lastname: Klose
authors.forename: Katarina
authors.initials: K
authors.lastname: Stingl
authors.forename: Miklos D
authors.initials: MD
authors.lastname: Resch
authors.forename: Anusch
authors.initials: A
authors.lastname: Hekmat
authors.forename: Anna
authors.initials: A
authors.lastname: Bruckmann
authors.forename: Kristof
authors.initials: K
authors.lastname: Karacs
authors.forename: Janos
authors.initials: J
authors.lastname: Nemeth
authors.forename: Ildiko
authors.initials: I
authors.lastname: Suveges
authors.forename: Eberhart
authors.initials: E
authors.lastname: Zrenner
mesh_terms: D000328:Adult; D001766:Blindness / Q000601:surgery*; D004567:Electrodes, Implanted; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care / Q000379:methods*; D019919:Prosthesis Implantation / Q000379:methods*; D012160:Retina / Q000473:pathology / Q000601:surgery*; D012174:Retinitis Pigmentosa / Q000601:surgery*; D016896:Treatment Outcome