CalibrateFI Tutorial

Importing and Calibrating the Fundus Collage

Open Plaque Simulator's Image window

If the Image window is not visible, bring it to the front by selecting the Images item from the Window menu.

In the Image window, click on the Fundus button in the Fundus button group. If the fundus image buffer is currently empty, PS will prompt you to open an image. If there is already a fundus image loaded, PS will simply display that image in the window. To clear the currently displayed image, use the Clear item of the Edit menu.

Opening a fundus collage file

If possible, have the Ophthalmologist provide the completed collage as a .jpg file or as a print that you can digitize on a flatbed scanner. Many fundus cameras provide collages now. If you receive a set of fundus pictures, the recommended method for creating a collage for Plaque Simulator is to use the Adobe Photoshop program to assemble the collage manually and export it as a .jpg file.

If the file navigation dialog does not automatically appear when you click the Fundus button, select Open File... from the File menu. The file navigation dialogs of PS are context sensitive; the types of files that are enabled for opening depend upon which PS window was frontmost when attempting to open a file. If the Image window was not frontmost when you selected Open File..., you may need to override the default context and select Image File from the File type: menu at the lower left of the file navigation dialog in order to enable access to image files.

Navigate to the patient folder (e.g. OsiriX Tutorial) in which you have saved the prepared images and select the fundus image (e.g. Fundus.jpg). Click the Choose button to continue.

Using the fundus ruler tool

The fundus calibration is critical because it establishes how the fundus image will be mapped onto the retinal surface of the 3D model, and thus the size and shape of the tumor base and where it is located within the eye.

After the fundus collage has loaded, click the Ruler button in the Fundus controls group to display the PS fundus calibration ruler tool.

The primary PS fundus ruler tool is a magenta line with yellow sizing control points (aka handles) at each end. One end is labeled Pole.
Click the cursor in the 'pole' handle and drag it over the posterior pole in the fundus collage.
Click the cursor in the unlabeled handle and drag it over the center of the optic disc in the fundus collage.
Select the number of collage photo centers from the menu in the Fundus controls (e.g. 3 in this example). Additional photo center markers will appear.
Important: The posterior pole marker is always considered as photo center #1, even if it is not exactly centered in a photo.
Drag the additional photo center markers (labeled 2 and 3 in this example) over the center of each of the photos that make up the collage.
Adjust the photo size slider (located just below the collage centers menu) so that the magenta circles surrounding each photo center marker match the photo edges.

Calibrating the fundus image

Next, click the Calib button adjacent to the Ruler button in the fundus group to open the Calibrate Image dialog.

Enter the physical distance from the center of the optic disc to the posterior pole.
Click the Import from eye model button to estimate this distance from a previously calibrated CT image.
Click the OK button to exit the dialog.

The calibrated fundus tool

When properly calibrated, the end of the fundus ruler centered on the optic disc should now have a 1 mm radius magenta circle surrounding it, just outside the border of the optic disc.

Properly calibrated fundus tool.

The number of photo centers

When the number of photo centers (3 total in this example) comprising the collage is set properly, the collage will map onto the 3D retinal surface with less distortion near the equator.

Only 1 collage center located at the posterior pole

3 centers reduces distortion near the equator

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