Zeiss CIRRUS HD-OCT 500, User Manual

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CIRRUS HD-OCT User Manual 2660021169012 Rev. A 2017-12
Anterior Segment
8-43
Angle-to-Angle Distance
Using Anterior Chamber Analysis
Click and drag the ends of ACD tool baseline to place the right and left endpoints in each
angle of the posterior portion of the Anterior Chamber, to measure the Angle-to-Angle
distance (ATA) or the Corneal Diameter. (Figure 8-27)
Using Wide Angle-to-Angle Analysis
The CIRRUS HD-OCT Wide Angle-to-Angle Analysis displays the Iris Viewport image and
one wide angle scan. The length, and angle of the scan are shown numerically in the Iris
Viewport. You may also use the Add Angle Tool(s) (
and ) or Caliper to
make manual measurements.
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NOTE: For Wide Angle-to-Angle, HD Angle, and Anterior Chamber Analyses, the Caliper
Tool
has additional functionality. Right-click the tool once it is placed on the image
and the Caliper Size Entry popup will appear, as shown to the left, and in Figure 8-28 .
Using these added functions you can type in a specific length of interest, and/or lock the
length of the caliper.
Corneal Thickness
Performance studies (see Tables 1, 2, 4 and 5 in Appendix C "CIRRUS HD-OCT
Repeatability and Reproducibility of Anterior Scan Measurements" , as well as
Table G18 in Appendix B "Study 5: Anterior Segment Accuracy, Repeatability
and Reproducibility" ), show that the repeatability of the central thickness measurement
from pachymetry is much better than the repeatability of the CCT as measured on the
Anterior Chamber scan or Anterior Segment 512x128 scan. In addition, the central
thickness measured in this manner has better agreement with Visante CCT. The improved
performance is likely due to the fact that the pachymetry measurement averages over a
3mm central area, while the Anterior Chamber scan depends on subjective placement of
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