Repeatability - Zeiss CIRRUS HD-OCT 500 User Manual

B-6
2660021169012 Rev. A 2017-12
Appendix
Table B-4: Difference between CIRRUS HD-OCT and Stratus OCT for the Central
Subfield Mean Thickness for each of the Six Categories.
N
1 – AMD 63 271.3 (60.6)
2 – DR 39 356.6 (118.7)
3 – VRI 45 386.3 (128.0)
4 – Other 53 310.6 (99.5)
5 – ME 35 351.1 (140.3)
6 – Normal 48 256.1 (18.6)

Repeatability

The repeatability of CIRRUS HD-OCT retinal thickness measurements varies with pathology.
Table B-5 shows the repeatability standard deviation for each disease category for the
central subfield average thickness. This is the expected standard deviation between two
scans acquired and analyzed using CIRRUS 3.0.
Repeatability can be improved by ensuring that two scans are registered to each other, as
when the Macular Change Analysis is used. Repeatability can also be improved using the
Macular Thickness Analysis in CIRRUS 4.0 when the fovea is correctly identified and used
as the reference point for subfield average thickness calculations. These repeatability
improvements are shown in Table
the fovea may fail in certain disease cases, as is shown in
always review the location of the fovea, and adjust it as necessary (see
Location" on page 8-6 for instructions on how to do this).
Repeatability when registration and fovea placement are performed is better than 9 μm for
all pathologies, which implies a coefficient of variability (repeatability standard deviation
divided by mean thickness) of 3.3% or better. Coefficient of variability is better than 1% for
normals.
Mean (SD) Difference CIRRUS – Stratus (μm)
CIRRUS Stratus
217.7 (54.2)
316.6 (135.8)
342.5 (125.0)
268.9 (101.6)
305.7 (127.9)
196.7 (18.6)
B-6. It is important to note that the algorithm to find
Difference
53.6 (35.0)
40.0 (47.1)
43.8 (35.9)
41.7 (47.1)
45.5 (45.3)
59.4 (11.7)
Table B-7. The user should
"Fovea
CIRRUS HD-OCT User Manual