Asymmetry evaluation of fundus images in right and left eyes using radon transform and fractal analysis

Asymmetry analysis is a challenging step in computerized early diagnosis of Diabetic retinopathy (DR) which provides an opportunity for early treatment. In this study to compare the patterns of vascular in right and left eyes, a combination of fractal analysis and radon transformation is investigated to provide both statistical distribution of the vessel thickness, and their geometrical distribution. For this purpose, the vessel segmentation and skeletonizetion are performed and the vessels' thickness map (VTM) is obtained. Then, the fractal dimension (FD) is found on various versions like the segmented vessels, skeletonized vessels, VTM, and radon transform (RT) of VTM in right and left eyes for asymmetry analysis. According to the obtained results for mean/SD values of the differences of FDs in right and left eyes and p-values, we conclude that RT of VTM is able to better discriminate two eyes from each other and accordingly, it can be used as a powerful feature for comparison of the symmetry/asymmetry in fundus images. Our evaluation results show that a difference of 0.33 ± 0.11 between FD of VTM's RT in left and right eyes is expected for normal subjects.