Anterior Segment Scans2660021169012 Rev. A 2017-12 CIRRUS HD-OCT User Manual6-16Guidelines for Wide Angle-to-Angle Acquisition• Attach the external Anterior Chamber lens to the instrument lens mount, see"Anterior Chamber and Cornea External Lenses" on page 6-7.• Instruct the patient to fixate on the center of the fixation target even though it maynot appear to be in focus.• If the anterior chamber seems tilted, instruct the patient to shift his/her gaze slightly tothe left or right as needed to horizontally orient the anterior chamber.• Click the center of the pupil and use the X, Y and Z controls or keyboard arrow keysand mouse scroll wheel to center the scan on the corneal vertex with both iridocornealangles, iris, and pupil visible in the OCT scan display area and the anterior of thecornea extending slightly out of the field of view, as shown in Figure 6-9.NOTE: A strong vertical central reflection line on the B-scan indicates the scan is centeredon the corneal vertex.NOTE: For the Wide Angle to Wide Angle scan, the iris will be slightly out of focus evenwhen correctly aligned.PachymetryThis scan consists of 24 radial scan lines with a scan depth of 2.0 mm that are used togenerate a color-coded thickness map of the cornea. The scan uses 24 B-scans, eachcomposed of 1024 A scans. This scan requires the Cornea external lens. The Pachymetryscan is used as the basis for the Pachymetry Analysis. (See "In Pachymetry Analysis"on page 8-44 for more information.)The Acquire screen displays the position of the Pachymetry scan pattern on the live irisimage. The images on the right display the temporal/nasal and inferior/superior scans ofthe selected meridian. The Pachymetry scan requires the Cornea external lens.
