Posterior Segment2660021169012 Rev. A 2017-12 CIRRUS HD-OCT User Manual8-14Select Review Registration to view the manually adjusted overlay. Use the slider above theoverlay, as needed, to change the transparency to see more of Image 1 or Image 2. Bymoving the slider back and forth, you can see if blood vessels or other features from oneimage align with the identical features in the other image. To return the registration to theoriginal setting, click the Reset Overlay button. If you are not satisfied with the positioningof the points, click the Undo button to delete all points and then make new pointselections.Darker areas on the lower registration screen occur where there is no data to compare. Thiswill occur when the data points selected create an offset of the images. To see the finalregistered image, move the slider all the way to the right. This black border will also beseen on the thickness map and the thickness difference map on the MCA screen. Whenyou are satisfied with the resulting overlay, select OK. To reset the values to the originalregistration, click Cancel.NOTE: If you or another user have changed the fovea location for any exam while carryingout Macula Thickness Analysis and the result has been saved, then that will be the fovealocation will be loaded.No RegistrationWhen No Registration is applied, the initial location of the ETDRS grid center for bothscans is taken from the value for the previous scan.The ETDRS Grid position circle is automatically positioned over the Fundus image of theolder scan data. You can adjust this position by clicking anywhere within the OCT scanboundary, and dragging the ETDRS Grid to a new position. Thickness values areautomatically recalculated corresponding to the new ETDRS Grid position.The Thickness Difference Map is seen at the far right of the display. It displays the thicknessdifferences between the two scan dates (current thickness minus prior thickness, inmicrometers) at each pixel location. The difference map has a different color scale torepresent the thickness change. This color map is indicated to the right. Warmer colorsindicate an increase in the thickness; cooler colors indicate a decrease in thickness. Thetransparency slider beneath each overlay can be adjusted, as required, to enhance the image.
