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Impressum
Decentration as a quality measure for topographic corneal recordings
Kramann C., Preußner P.-R., Wahl J.
Department of Ophthalmology, Johannes-Gutenberg University, Langenbeckstr.1, 55101 Mainz, Germany
Objective: The purpose of this paper is to get a quality measure
to control the quality of corneal video topographies. Information about
the precision of the corneal topography is indespensable as it is needed
as an accurate basis for following refractive surgery ("customized"
surgery).
Methods: On the basis of a two-dimensional cross correlation, a
cartesian curve (ellipsis, parabola, hyperbola) which gives the best fit
to the data was approximated numerically. The quality measure was the
decentration parameter d which was only derived from the corneal topography
itself. The topometric data has been recorded by the Technomed C-Scan.
100 video topographies were evaluated, eyes which had undergone laser
refractive surgery or corneal injuries were excluded.
Results: The median of the decentration parameter d has the unexpected
low value of 0,086 mm. In poor corneal recordings, the decentration can
be more than 1 mm, in these cases decentration can be visualized also
directly.
Conclusion: The decentration parameter d derived here is a useful
quality measure for topographic corneal recordings.