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Impressum
The digital confocal laser scanning microscopy in vivo of keratocytes with a modified Heidelberg Retina Tomograph (HRT 1)
Stave J., Torens S., Käppel K., Guthoff R.
Eye Depatartment, University of Rostock, 18057 Rostock
Background: Insufficient imaging quality and irregular corneal
illumination are the main problems for automatical quantitative evaluation
the density of keratocytes when applying confocal tandem scanning microscopes
with halogen- or mercury-lamps. A high expenditure for correcting the
background irregularities of images is required. The aim of this study
was to to convert the HEIDELBERG RETINA TOMOGRAPH HRT into a highresolution
digital laser scanning microscope for visualization of the anterior segment
of the eye.
Material and Method: We have developed a z-scan contact lens adapter
for the original front lens of the HRT in order to focus the laser beam
in the cornea by combining with an external computer controlled hydraulic
scan sledge for shift the focus plane through the cornea. By using a programmable
electronic device for the external stepmotor on the hydraulic motion drive
of the z-scan unit under employment the internal control functions it
is possible to create a digital confocal laser scanning microscope. under
preservation of all original HRT functions including the patient data
bank. For automatically evaluation the confocal corneal image series we
use a modified CHEMOTAXIS® -software.
Results: First confocal images of healthy corneae shows a good
and regular illumination of the epithelium, endothelium and keratocytes
as well as a very sharp dissolve of the confocal planes. In the first
time with the confocal laser microscope the intercelluar connections of
the ceratocytes can be depicted wich is unpossible with in vivo confocal
ligth microscope. The hydraulic z-scan allows a precise shift of the focus
plane through the cornea to record confocal series of images of the keratocytes.
Conclusion: The in vivo confocal laser scanning microscopy permits
a regular illumination of the whole scanning field with high resolve.
This is a good condition for the automatically evaluation of the keratocytes
and its density in different dephts of the cornea. The modified HRT is
a useful alternative for the ligth tandem scanning microscopy, e.g. before
and after PRK or LASIK. The developed computer-controlled lens adapter
is a pratical upgrading the HRT functions without loss of original functions.