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.