Zeiss CIRRUS HD-OCT 500, User Manual

Page: 174 / 352

Anterior Segment
2660021169012 Rev. A 2017-12 CIRRUS HD-OCT User Manual
8-52
The values S-I are calculated by subtracting the average value in the I sector at the
specified distance from the center, from the average value in the S sector, at the
corresponding distance.
Likewise, The values SN-SI are calculated by subtracting the average value in the SI sector
at the specified distance from the center, from the average value in the SN sector, at the
corresponding distance.
Central Corneal Thickness (CCT) Measurement
Central corneal measurements should be made at the apex of the cornea using the
Anterior Segment Cube 512x128 Cube Analysis or the Anterior Segment 5 Line Raster. To
determine the apical area:
1. Estimate where the center of the pupil is on the image and move the scan navigators
so that they intersect at that point.
2. Click the Caliper button, and align the Caliper vertically against the magenta slice
navigator on the horizontal scan.
3. The center of the cornea can be identified by moving the scan navigators throughout
the entire scan volume and noting how the scans appear to move up and down within
the box. The apical area, being closest to the instrument lens, will have the highest
scans. By using the Caliper as a reference point while moving the slice navigators, find
the highest horizontal and vertical scans.
4. The CCT measurement should be made at the intersection of the highest horizontal
and vertical scans, using the Caliper on the horizontal scan. The intersection of the
scans is identified by the position of the mauve slice navigator. Adjust the position of
the Caliper and place the white horizontal lines of the Caliper ends on the anterior and
posterior surfaces of the cornea. The measurement is in micrometers. See
Figure
8-37 for the correct position of the Caliper and the proper placement of the calipers.
cáÖìêÉ=UJPT=mçëáíáçåáåÖ=íÜÉ=`~äáéÉê