Color fundus image registration techniques and applications for automated analysis of diabetic retinopathy progression: A review

Diabetic retinopathy (DR) is one of the leading cause of visual impairments in the working age population in the developed world. It is a complication of both types of diabetes mellitus, which affects the light perception part of the retina; and without timely treatment patients could lose their sight and eventually become blind. Automated methods for the detection and progression analysis of DR are considered as potential health-care need to stop disease propagation and to ensure improved management for DR. Aiming for the detection and progression analysis of DR, color fundus photography is considered as one of the best candidates for non-invasive imaging of the eye fundus. A list of methods has already been developed to analyse DR related changes in the retina using color fundus photographs. In this manuscript we review those automated methods. In order to accurately compare the evolution of DR over time, retinal images that are typically collected on an annual or biennial basis must be perfectly superimposed. However, in reality, for two separate photographic-eye examinations the patient is never in exactly the same position and also the camera may vary. Therefore, a registration method is applied prior to evolution computation. Knowing registration as a fundamental preprocessing step for longitudinal (over time) analysis, we also reviewed state-of-the art methods for the registration of color fundus images. The review summarizes the achievement so far and also identifies potential study areas for further improvement and future research toward more efficient and accurate DR progression analysis. (C) 2018 Elsevier Ltd. All rights reserved.