title: Optical cylinder designs to increase the field of vision in the osteo-odonto-keratoprosthesis.
abstract: BACKGROUND
  The single optical cylinders used in the osteo-odonto-keratoprosthesis (OOKP) are known to produce very small visual fields. Values of 40 degrees are typically quoted. The purpose of this paper is to present designs for new optical cylinders that significantly increase the field of view and therefore improve the visual rehabilitation of patients having an OOKP.
  
  
  METHODS
  Computer ray-tracing techniques were used to design and analyse improved one- and two-piece optical cylinders made from polymethyl methacrylate. All designs were required to have a potential visual acuity of 6/6 before consideration was given to the visual field and optimising off-axis image quality. Aspheric surfaces were used where this significantly improved off-axis image quality.
  
  
  RESULTS
  Single optical cylinders, with increased posterior cylinder (intraocular) diameters, gave an increase in the theoretical visual field of 18% (from 76 degrees to 90 degrees) over current designs. Two-piece designs based on an inverted telephoto principle gave theoretical field angles over 120 degrees. Aspheric surfaces were shown to improve the off-axis image quality while maintaining a potential visual acuity of at least 6/6. This may well increase the measured visual field by improving the retinal illuminance off-axis.
  
  
  CONCLUSIONS
  Results demonstrate that it is possible to significantly increase the theoretical maximum visual field through OOKP optical cylinders. Such designs will improve the visual rehabilitation of patients undergoing this procedure.
authors.affiliation: Centre for Applied Vision Research, The City University, Northampton Square, London, EC1V 0HB, UK. C.C.Hull@city.ac.uk
authors.forename: C C
authors.initials: CC
authors.lastname: Hull
authors.forename: C S
authors.initials: CS
authors.lastname: Liu
authors.forename: A
authors.initials: A
authors.lastname: Sciscio
authors.forename: H
authors.initials: H
authors.lastname: Eleftheriadis
authors.forename: J
authors.initials: J
authors.lastname: Herold
mesh_terms: D017076:Computer-Aided Design; D003316:Corneal Diseases / Q000534:rehabilitation*; D055095:Optics and Photonics / Q000295:instrumentation; D019904:Polymethyl Methacrylate; D019736:Prostheses and Implants; D011474:Prosthesis Design; D014786:Vision Disorders / Q000534:rehabilitation*; D014792:Visual Acuity; D014794:Visual Fields
chemical_list: D019904:Polymethyl Methacrylate