Preparing the Fundus Collage

In the Image Window open a fundus image. For best results, the image should be less than than 800 pixels wide and the background color should be black.

  • Load a fundus image into the fundus image buffer.
  • Enable the fundus Ruler tool.
  • Mark the center of the disc and the posterior pole. The pole marker is always assumed to be the center of the image, or the center of a collage component.
  • If the fundus image is a collage of multiple narrow angle components:
    • From the Collage centers menu select the number of components (e.g. 3). Note: although this example collage was composited from 4 images, only 3 of the images need be marked since the 2nd and 3rd components overlap nearly all of the 4th.
    • Drag the center markers of collage components 2 and 3 to their appropriate locations and adjust the range slider to fit the components. PS uses these markers to estimate the fundus camera orientation associated with each pixel when mapping collage pixels to 3D and polar map coordinates.
  • In the fundus control group, click the Calib. button to calibrate the fundus collage.
  • In the calibration sheet, enter the distance between the pole and disc center in mm. This is usually done by importing that distance from the eye model which has been previously fit to a calibrated axial CT or MR image.
  • Choose the background transparency color (e.g. black).
  • Click the OK button to exit the calibration sheet.

Mapping the raw fundus image onto the Retinal Diagram

In the Diagram Window:

  • Enable the Photo button to display the fundus image.
  • The pole should be at the diagram center, the disc should just inside the orange disc circle.

Adjusting the fundus image transparency

In the Diagram Window, control-click (or right mouse button) the Photo button to reveal a contextual menu. Adjust the transparency slider in the menu to remove as much background as possible without losing image quality.

Transparency level 0


Transparency level 1


Transparency level 16


Warping the fundus collage to the retinal diagram

The circumferential warping required of image pixels near the posterior pole is small, but becomes significant as one approaches the equator and crosses to the anterior hemisphere of the eye. Fundus images consisting of a single photo obtained with a wide angle lens will already include the required pixel warp. Fundus collages composited from several photos taken using a narrow angle lens will need to be warped as a function of their distance from the central ray of whichever photo they are from in order to display correctly on the retinal diagram.

Note: By default, PS automatically warps the tumor and fundus collage after digitizing the tumor. You may also manually warp (or unwarp) the fundus image at any time.

  • For best results, enable Auto Correct Tumor in the Diagram and digitize the tumor perimeter using the raw (unwarped) collage. PS defaults to digitizing the tumor using the raw image so as to have the best possible image quality while digitizing the tumor perimeter. After the tumor perimeter is complete, PS will apply the necessary circumferential warping of the tumor perimeter.
  • The warped tumor perimeter will no longer match the underlying collage!
  • After digitizing the tumor PS will offer to warp the collage.
  • PS will then circumferentially warp the pixels of the collage. The digitized tumor perimeter should now better match the underlying image.
  • It is allowable to warp the collage first and then digitize the tumor by disabling Auto Correct Tumor in the Diagram menu prior to digitizing the tumor perimeter.
  • To manually warp the fundus collage, from the Photo button contextual menu, simply enable Auto Correct Collage.