Zeiss CIRRUS HD-OCT 500, User Manual

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Posterior Segment
2660021169012 Rev. A 2017-12 CIRRUS HD-OCT User Manual
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RNFL & ONH Guided Progression Analysis
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RNFL Thickness Profiles
The RNFL Thickness Profiles ( Figure 8-21 ) plot RNFL thickness values around the CIRRUS
RNFL Calculation Circle. All of the OCT Fundus images are overlaid with the red circle that
shows where the thickness profile measurements are evaluated. The location of the red
circle on the first baseline exam is determined by the automatic algorithm that finds the
center of the optic disc. Because the remaining scans are registered to the first baseline
scan, the same center and circle are used for all other scans.
There are three curves: two for the current baseline exams shown in gray (labeled B1 and
B2), and one for the most recent examination shown in blue (labeled C for current). The
profile analysis identifies moderate focal thinning in the RNFL thickness by comparing
observed change in the RNFL Thickness Profiles to test–retest variability, and then looking
for instances where the apparent change is confirmed over multiple visits.
For “Likely Loss”, “Possible Loss”, or “Possible Increase”, to be reported, at least 14
adjacent A-scans must show significant change. This value was chosen to allow the TSNIT
profile to be sensitive to defects of 20–degrees or more. Areas between the baseline pair
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2
3
4
5
1 RNFL Thickness Profiles 4 RNFL Thickness Change maps
2 RNFL Summary 5 RNFL Thickness maps
3 Average RNFL Thickness Graphs