Zeiss CIRRUS HD-OCT 500, User Manual

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CIRRUS HD-OCT User Manual 2660021169012 Rev. A 2017-12
Appendix
B-19
Study 5: Anterior Segment Accuracy, Repeatability and Reproducibility
Benchtop Scanning Accuracy, Repeatability and Reproducibility
Accuracy, repeatability, and reproducibility of scanning in the CIRRUS HD-OCT have been
measured in benchtop studies.
Table B-17 below summarizes the results for axial
dimensions in the basic image geometry.
Accuracy is reported as a 95% confidence interval for the absolute difference between a
measured and actual distance. Repeatability and reproducibility are given both as standard
deviation (SD) estimates and as estimates for the 95% upper limit of the difference
between two measurements. The Repeatability Limit = 2.8 X Repeatability SD. The
Reproducibility Limit = 2.8 X Reproducibility SD.
Table B-17: Repeatability and Reproducibility of Axial Distance in Tissue
CIRRUS HD-OCT Repeatability in Measuring Central Corneal
Thickness
A study was conducted to determine repeatability and reproducibility of the CIRRUS
HD-OCT instrument measurements of Central Corneal Thickness (CCT). Phase I of the study
enrolled 28 subjects and was designed to determine inter–device variability, wherein each
subject was imaged 3 times during a single visit on each of three CIRRUS OCT instruments
by one operator. Phase II enrolled 22 subjects and was designed to determine inter–
operator variability, wherein each subject was imaged three times during a single visit by
each of three operators. Phases I and II enrolled different subjects.
The CIRRUS HD-OCT repeatability and reproducibility are shown in Table B-18 . Mean
thickness of each phase and overall (Phase I and II combined) are also shown. Since the
random error variability from Phase II of the study was larger than that from Phase I, the
variance components from Phase II were used to estimate the random measurement
variability and the repeatability standard deviation.
Measurement Accuracy
( μ m)
Repeatability
SD ( μ m)
Repeatability
Limit
a
( μ m)
Reproducibility
SD ( μ m)
Reproducibility
Limit
b
( μ m)
Average
Measurement
( μ m)
Axial Distance in Tissue 6.2 2.6 7.1 2.7 7.6 1165.6
a. Repeatability Limit is the upper 95% limit for the difference between repeated results. Per ISO 5725–1 and ISO 5725–6, Repeatability Limit = 2.8 x Repeat-
ability SD.
b. Reproducibility Limit is the upper 95% limit calculated for the difference between individual measurements using different operators and instruments. Each
test object was imaged three times by two operators on each of five instruments. Per ISO 5725–1 and ISO 5725–6, Reproducibility Limit = 2.8 x Reproduc-
ibility SD.