August 2019
Volume 60, Issue 11
Open Access
ARVO Imaging in the Eye Conference Abstract  |   August 2019
Non-contact, laser-based confocal microscope for corneal imaging
Author Affiliations & Notes
  • Michele Pascolini
    NIDEK Technologies Srl, Albignasego, Italy
  • Federico Carraro
    NIDEK Technologies Srl, Albignasego, Italy
  • Nicola Codogno
    NIDEK Technologies Srl, Albignasego, Italy
  • Mattia Minozzi
    NIDEK Technologies Srl, Albignasego, Italy
  • Ronnye Pajaro
    NIDEK Technologies Srl, Albignasego, Italy
  • Christian Tiso
    NIDEK Technologies Srl, Albignasego, Italy
  • Giulia Menin
    NIDEK Technologies Srl, Albignasego, Italy
  • Simone Pajaro
    NIDEK Technologies Srl, Albignasego, Italy
  • Cesare Tanassi
    NIDEK Technologies Srl, Albignasego, Italy
  • Footnotes
    Commercial Relationships   Michele Pascolini, NIDEK Technologies Srl (E); Federico Carraro, NIDEK Technologies Srl (E); Nicola Codogno, NIDEK Technologies Srl (E); Mattia Minozzi, NIDEK Technologies Srl (E); Ronnye Pajaro, NIDEK Technologies Srl (E); Christian Tiso, NIDEK Technologies Srl (E); Giulia Menin, None; Simone Pajaro, NIDEK Technologies Srl (E); Cesare Tanassi, NIDEK Technologies Srl (E)
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science August 2019, Vol.60, 014. doi:https://doi.org/
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    • Get Citation

      Michele Pascolini, Federico Carraro, Nicola Codogno, Mattia Minozzi, Ronnye Pajaro, Christian Tiso, Giulia Menin, Simone Pajaro, Cesare Tanassi; Non-contact, laser-based confocal microscope for corneal imaging. Invest. Ophthalmol. Vis. Sci. 2019;60(11):014. doi: https://doi.org/.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Confocal microscopy is an effective technique for the direct observation of corneal pathologies. In this work a non-contact laser confocal microscope (CS-5) is presented, whose images are enhanced by an image fusion technique to obtain sharp details and a uniform field of view for any layer from epithelium to endothelium.

Methods : CS-5 takes 1-Mpixel images at 18 fps with a Field of View of 400x400 µm2 at a distance of 12 mm from the patient’s corneal apex. Provided that in such conditions corneal images can be acquired only imposing a high confocality to carefully suppress aberrations and reflexes, the design is based on two micrometric apertures and a 2D scanning head. A red laser is used as a source and an Avalanche Photo-Diode (APD) as a detector.
The confocality is so narrow that some details might fall out of focus in a given frame. Sequences of images are thus recorded by means of a micrometric z-scan and combined in stacks of about 5 images for endothelium, stroma and epithelium, respectively.
After a pre-processing to reduce the noise, the possible motion is compensated by frame registration. Each resulting image is successively filtered with a moving-average spatial filter. The stack of registered images is processed with a majority filter to produce a depth map containing, for each pixel, the index of the slice having the best focus at that point. Finally, a composite image is created from the stack by selecting pixels as indicated by the depth map.

Results : We tested the CS-5 on healthy patients. Acquired images show the nuclei of the endothelial cells, posterior and anterior stroma, sub-basal nerve plexus, basal cells and tear film. Raw images present good resolution but are crispy and lack the depth of focus.
We evaluated the image fusion on stacks of 5-6 images of the epithelium, stroma and endothelium of enucleated pig eyes. Composite images showed that the processing algorithm enhances the overall focus and the anatomical details.

Conclusions : The CS-5 is a novel corneal confocal microscope that operates in non-contact conditions minimizing the invasiveness of the examination. Image quality is comparable with contact microscopes whilst the limited depth of focus has been extended by means of image fusion, applying image registration and a majority filter.

This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.

 

Corneal layers from the endothelium to the epithelium on healthy patients

Corneal layers from the endothelium to the epithelium on healthy patients

 

Above: sequence of 8 pig endothelium images. Below: depth map and image fusion result

Above: sequence of 8 pig endothelium images. Below: depth map and image fusion result

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