Purpose: Diabetic retinopathy (DR) is characterized by retinal lesions affecting people having diabetes for several years. It is one of the leading causes of visual impairment worldwide. To diagnose this disease, ophthalmologists need to manually analyze retinal fundus images. Computer-aided diagnosis systems can help alleviate this burden by automatically detecting DR on retinal images, thus saving physicians’ precious time and reducing costs. The objective of this study is to develop a deep learning algorithm capable of detecting DR on retinal fundus images. Nine public datasets and more than 90,000 images are used to assess the efficiency of the proposed technique. In addition, an explainability algorithm is developed to visually show the DR signs detected by the deep model.

Approach: The proposed deep learning algorithm fine-tunes a pretrained deep convolutional neural network for DR detection. The model is trained on a subset of EyePACS dataset using a cosine annealing strategy for decaying the learning rate with warm up, thus improving the training accuracy. Tests are conducted on the nine datasets. An explainability algorithm based on gradient-weighted class activation mapping is developed to visually show the signs selected by the model to classify the retina images as DR.

Result: The proposed network leads to higher classification rates with an area under curve (AUC) of 0.986, sensitivity = 0.958, and specificity = 0.971 for EyePACS. For MESSIDOR, MESSIDOR-2, DIARETDB0, DIARETDB1, STARE, IDRID, E-ophtha, and UoA-DR, the AUC is 0.963, 0.979, 0.986, 0.988, 0.964, 0.957, 0.984, and 0.990, respectively.

Conclusions: The obtained results achieve state-of-the-art performance and outperform past published works relying on training using only publicly available datasets. The proposed approach can robustly classify fundus images and detect DR. An explainability model was developed and showed that our model was able to efficiently identify different signs of DR and detect this health issue.