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Visual Optics and Biophotonics Lab - CSIC - Madrid


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Funding - FEDER
Technology Transfer
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Scheimpflug imaging

 Selected references

  Rosales et al. 2006
  de Castro et al. 2007
  Rosales and Marcos 2009
  Perez-Escudero et al. 2009

 New Instruments

  Laser Ray Tracing
  Hartmann Shack
  Adaptive Optics
  Gradient index-LRT
  Purkinje Imaging System
  Scheimpflug Imaging
  Anterior Segment OCT
  Structured Illumination Corneal Microscopy

 Scheimpflug Imaging

Scheimpflug imaging allows imaging the anterior segment of the eye with a relatively large depth of focus, which is tilting the imaging plane with respect to the optical axis of the instrument. Scheimpflug images suffer from geometrical distortion (which arises from the geometrical configuration of the system) and optical distortion (due to the refraction from the preceding ocular surfaces).
In a collaborative study with Michael Dubbelman and Rob van der Heijde we have validated (against Purkinje imaging) the accuracy of a refurbished Topcon Scheimpflug system (out of the market) to retrieve the anterior and posterior lens radii of curvature, once geometrical and optical distortion correction algorithms were applied (Rosales et al. 2006)
Subsequent studies were developed using a recently commercialized Scheimpflug system (Pentacam, by Oculus). We have demonstrated the capability and accuracy of measuring intraocular lens tilt and decentration with the Scheimpflug Pentacam system, validated against  Purkinje imaging (de Castro et al 2007)
We have demonstrated that the Pentacam system is a reliable system to assess the changes in the posterior corneal surface. We have developed eye models for calibrating the system. Spherical surfaces of known radii of curvature were used to assess the accuracy of the anterior corneal measurements. A hybrid porcine-plastic eye model was developed to assess the accuracy of the posterior corneal measurements. The cornea had similar scattering properties and refractive index as real corneas, while the supporting surface for the posterior cornea had known radii of curvature. (PĂ©rez-Escudero et al 2009)
We have developed our own algorithms for geometrical and optical distortion correction in Pentacam Scheimflug system, so that it can be used not only as a corneal topographer but for realiably measuring the geometry of the crystalline lens. We have validated the method with artificial eyes of known geometry as well as in subjects previously measured with Purkinje and a validated Scheimpflug system. (Rosales and Marcos 2009)