title: [Improvement of power and illumination source of the indirect binocular ophthalmoscope designed by Foerster].
abstract: BACKGROUND
  Since 1982, the indirect binocular ophthalmoscope designed by Foerster has been in use in ophthalmology. The option to implement a new illumination technique using a light-emitting diode (LED) and a new power source should be evaluated in terms of technical feasibility and patient safety.
  
  
  METHODS
  The cooling element was redesigned to accommodate the new LED electronics and their components, including an option for a variable brightness control. A more compact rechargeable battery was utilized with variable fixation at the headband or elsewhere. Photometric measurements of light intensity and the operating time were planned. Furthermore, a review of the new lighting technology in terms of EN ISO 15004-2 and EN ISO 10943 was necessary.
  
  
  RESULTS
  Technical adjustments to accommodate the LED inside the cooling element could be realised. The power source was a modern rechargeable lithium-ion battery with variable fixation. The luminous intensity of the LED is superior to that of the halogen lamp and the operating time was increased to 520 minutes. The required limits according to DIN EN ISO 15004-2 for ophthalmic devices were met by our measurements.
  
  
  CONCLUSIONS
  The optimisation of the indirect binocular ophthalmoscope brings improvements in illumination intensity and operating time. A conversion for models already in use is possible. A certified appraisal for compliance with the appropriate standards is the next step.
authors.affiliation: Department für Augenheilkunde, Universitäts-Augenklinik, Tübingen. martin.leitritz@med.uni-tuebingen.de
authors.forename: M A
authors.initials: MA
authors.lastname: Leitritz
authors.forename: T
authors.initials: T
authors.lastname: Oltrup
authors.forename: H
authors.initials: H
authors.lastname: Umesh Babu
authors.forename: T
authors.initials: T
authors.lastname: Bende
authors.forename: K U
authors.initials: KU
authors.lastname: Bartz-Schmidt
authors.forename: M H
authors.initials: MH
authors.lastname: Foerster
mesh_terms: D011211:Electric Power Supplies; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005240:Feasibility Studies; D008029:Lighting / Q000295:instrumentation*; D008904:Miniaturization; D019721:Ophthalmoscopes; D015203:Reproducibility of Results; D012666:Semiconductors; D012680:Sensitivity and Specificity