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000000Ć1150Ć839 IOLMaster 11.02.2004
Note:
In this case, "Borderline SNR" does not mean a wrong result, but
shall only remind you to verify this measurement!
Accurate signal peaks can be determined by comparison with other
values of the measurement series of this eye (and of the other eye, if
necessary). See also the sections "Example signal curves of axial length
measurements", p. 53, and "Shifting the measuring cursor" below.
SNR < 1.6 (The measured value is unusable)
It is marked on the display as an erroneous result (Fig. 45).
This implies that the true measuring signal does not clearly stand out
from noise. As a rule, the results of such measurements are not usable
and should be deleted. You may delete them from the list by using the
<DEL>
key once they are highlighted.
Note:
Erroneous results (display: Error) are not considered in mean value
calculation!
The measured value may be transferred to the list of measured values
by a click on the measuring cursor (white dot).
See to it that the measured values are consistent.
Shifting the measuring cursor
The measuring cursor (white point) is automatically placed on the center
of the signal peak with the highest absolute amplitude. The corresponĆ
ding axial length value is displayed beside the graph and in the display
field. The SNR is calculated and displayed for this signal peak. The
measuring cursor is placed in the center between the regions corresponĆ
ding to half the maximal amplitude. If the signal curve is symmetrical
(Gaussian curve), the cursor is positioned exactly above the maximum
of the signal. For interpretation of axial length measurements (p. 60) it
may be necessary to shift the measuring cursor to verify axial length
agreement between values in a measurement series.
There are two ways to move the measuring cursor to another peak. In
both cases, it is advisable to do this with the signal curve being zoomed:
1. Automatic positioning on a "remote" peak:
Place the mouse (arrow) cursor in the measuring cursor (white point).
Holding the left mouse button depressed move the measuring cursor
over the desired peak. A vertical blue line will appear below the
measuring cursor for easier orientation. This line will be moved along
with the cursor.
When you release the mouse button, the measuring cursor will
automatically "snap in" over the desired peak.
Fig. 45 Erroneous result
Evaluation of ALM results
