Zeiss CIRRUS HD-OCT 500, User Manual

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CIRRUS HD-OCT User Manual 2660021169012 Rev. A 2017-12
Overview
9-5
NOTE: The Avascular slab was constructed with the goal of bounding the parts of the
retina that are expected to have no vasculature in normal anatomy. There are many
situations for which there may appear to be bright patches or areas in this image that are
not necessarily due to pathology, including:
Errors in segmentation may cause there to be apparent vasculature. This is particularly
common in the presence of geographic atrophy. Bright areas below the Bruch’s Membrane
are common in the presence of geographic atrophy due to the fact that the highly
scattering RPE is missing. When this happens, the RPE segmentation can frequently fall
into the choroidal areas and be irregular.
Because the boundaries of the inner layers of the retina are estimated rather than
segmented, they may incorrectly include bright areas that could contain decorrelation tails
or even actual vasculature.
The brightness and contrast of the avascular layer is enhanced in order to assist in
visualizing any potential abnormal vasculature, but this can also tend to emphasize both
noise and weak decorrelation tail signals.
Exudates or migrated RPE may cause there to be artifacts in different layers. This issue
should be uncommon in the outer retina, but it can occur.
The segmentation and flow and intensity B-scans should be examined carefully if there is
abnormal-appearing vasculature in the Avascular slab.
NOTE: This preset is not available for ONH Angiography.
• Choriocapillaris: The inner surface is 29 μ m below the RPE-Fit and the outer surface is
49 μ m below the RPE-Fit, therefore the slab has a uniform thickness of 20 μ m.
NOTE: This preset is not available for ONH Angiography.
• Choroid: The inner surface is 64 μ m below the RPE-Fit, which is segmented as
described in " Advanced Visualization Analysis" on page 8-68 . This is
intended as an estimate of the Bruch’s Membrane (BM). The outer surface is 115 μ m
below the RPE-Fit, therefore the slab has a uniform thickness of 51 μ m.
NOTE: This preset is not available for ONH Angiography.
• ORCC: The OCT Analysis uses a predefined Outer Retina to Choriocapillaris (ORCC)
slab that covers the region between the outer retina and choriocapillaris layers. The
ORCC slab uses a Pixel option that can calculate the pixel values or maximum
pixel values. The ORCC preset is the default preset and is defined as follows:
Top: OPL=RPE-Fit - 110
μ m
Bottom: RPE-Fit + 38 μ m
NOTE: This preset is not available for ONH Angiography.