title: Portable light transmission measuring system for preserved corneas.
abstract: BACKGROUND
  The authors have developed a small portable device for the objective measurement of the transparency of corneas stored in preservative medium, for use by eye banks in evaluation prior to transplantation.
  
  
  METHODS
  The optical system consists of a white light, lenses, and pinholes that collimate the white light beams and illuminate the cornea in its preservative medium, and an optical filter (400-700 nm) that selects the range of the wavelength of interest. A sensor detects the light that passes through the cornea, and the average corneal transparency is displayed. In order to obtain only the tissue transparency, an electronic circuit was built to detect a baseline input of the preservative medium prior to the measurement of corneal transparency. The operation of the system involves three steps: adjusting the "0 %" transmittance of the instrument, determining the "100 %" transmittance of the system, and finally measuring the transparency of the preserved cornea inside the storage medium.
  
  
  RESULTS
  Fifty selected corneas were evaluated. Each cornea was submitted to three evaluation methods: subjective classification of transparency through a slit lamp, quantification of the transmittance of light using a corneal spectrophotometer previously developed, and measurement of transparency with the portable device.
  
  
  CONCLUSIONS
  By comparing the three methods and using the expertise of eye bank trained personnel, a table for quantifying corneal transparency with the new device has been developed. The correlation factor between the corneal spectrophotometer and the new device is 0,99813, leading to a system that is able to standardize transparency measurements of preserved corneas, which is currently done subjectively.
authors.affiliation: Departamento de Engenharia Elétrica, Universidade de São Paulo, EESC-USP, São Carlos, SP, Brazil. liliane@sel.eesc.usp.br
authors.forename: Liliane
authors.initials: L
authors.lastname: Ventura
authors.forename: Gabriel Torres de
authors.initials: GT
authors.lastname: Jesus
authors.forename: Gunter Camilo Dablas de
authors.initials: GC
authors.lastname: Oliveira
authors.forename: Sidney J F
authors.initials: SJ
authors.lastname: Sousa
mesh_terms: D003315:Cornea / Q000502:physiology*; D003318:Corneal Opacity / Q000175:diagnosis / Q000503:physiopathology; D019781:Corneal Topography / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005125:Eye Banks / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D008029:Lighting / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D042261:Retinoscopes; D042262:Retinoscopy / Q000379:methods; D012680:Sensitivity and Specificity; D014021:Tissue Preservation / Q000295:instrumentation* / Q000379:methods