Scan Acquisition Controls; Scan Pattern Adjustments; Aligning Scans Corrected For Beam Scanning Geometry And Corneal Refraction; Center Corneal Scans On The Corneal Vertex - Zeiss CIRRUS HD-OCT 500 User Manual

Anterior Chamber and Cornea External Lenses

CIRRUS HD-OCT User Manual

Scan Acquisition Controls

Not all posterior scan acquisition controls are available for anterior segment scans. For
anterior segment scans:
• There is no fundus image, and therefore the Auto Focus button and Z controls (left–
right Focus arrows) are not displayed. However, the Focus bar is still displayed,
showing the last focus for the patient.
• FastTrac is not available for anterior segment scans, and therefore the three FastTrac
buttons below the Capture button are not displayed.
• The Optimize button is available only for Anterior Segment Cube 512x128 and Anterior
Segment 5 Line Raster scans.
• The Auto–Enhance button, the Auto–Center button, and manual–center controls are
not available. The OCT display can be centered vertically in the live OCT window by
using the chinrest control buttons or the mouse scroll wheel. However, the shift key +
mouse scroll wheel does not bring the scan into the acquisition window for anterior
scans as it does for posterior scans.

Scan Pattern Adjustments

The scan pattern for anterior scans is displayed on the iris image. The scan pattern cannot
be moved, and scan length is not adjustable. Rotation and line spacing are adjustable for
the Anterior Segment 5 Line Raster scan. Rotation is adjustable for the HD Angle, HD
Cornea, Anterior Chamber, and Wide Angle-to-Angle scans. For more information on
adjusting scan patterns, see "Scan Pattern Adjustments" on page
Aligning Scans Corrected for Beam Scanning Geometry and
Corneal Refraction
Anterior Chamber, Wide Angle-to-Angle, HD Cornea, HD Angle, and Pachymetry scans are
corrected to account for beam scanning geometry and refraction on the corneal surfaces.
These corrections are most accurate when acquired corneal scans are centered on the
corneal vertex, which generates a strong central reflection line on the live OCT image.
Typically the corneal vertex is just to the nasal side of the pupil center.

Center Corneal Scans on the Corneal Vertex

NOTE: HD Angle scans are not
1. Instruct the patient to fixate on the center of the fixation target, even though it may not
appear to be in focus.
2. Follow the alignment guidelines for each scan to position the scan in the OCT viewport,
making adjustments until there is a strong central reflection line indicating the scan is
centered on the corneal vertex.
Four anterior segment scans require an external lens:
Anterior Chamber External Lens:
• Anterior Chamber Scan
Anterior Segment Scans
aligned to the corneal vertex.
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