Ultrawide field FA
Another available technology that fills the need for more extensive views in the eye is ultrawide FA. A comparison of SS-OCT images that were montaged into a larger image and images obtained using ultrawide FA showed that the former had better resolution than the latter. However, the SS-OCT images do not capture as extensive a view as the ultrawide FA when the images are montaged, Dr. Waheen reported.
“Imaging could theoretically go much further out to the equator or beyond,” Dr. Waheed explained. “However, as the field becomes increasingly wider, the problem that arises is that a spherical surface is attempting to be represented as a flat surface. We know from cartography that this leads to a great deal of distortion, especially in the peripheral areas where structures seem to occupy a larger area than they truly occupy.”
Dr. Waheed and colleagues, in collaboration with Ruikan (Ricky) Wang, PhD, director, Biophotonics and Imaging Laboratory, Department of Bioengineering, University of Washington, Seattle, have attempted to correct for this peripheral distortion that appears when montaging images to obtain a wider field of view.
“The distortion can be corrected by displaying the image as a virtual three-dimensional projection or as a flat corrected image,” Dr. Waheed said, noting that after the correction software is applied, the areas of non-perfusion in the periphery appear much smaller than in the uncorrected image.