Optic Disc Fundus Images Retain Biometric Identity Signals Under Deep Learning

This work investigated whether deep learning models trained on optic disc-centered fundus images retain sufficient subject-specific information for biometric verification compared with models trained on full-field fundus photographs. A total of 30,836 color fundus photographs from 7,724 eyes of 4,500 subjects were obtained at the Bascom Palmer Eye Institute. Each fundus photograph was processed into three image representations: full-field fundus, optic disc region including 0.5 disc diameters of peripapillary retina, and tightly cropped optic disc only. Images were partitioned at the subject level into training (70%), validation (10%), and test (20%) sets. Separate Siamese convolutional neural network models were trained for each image type using triplet loss to learn subject-discriminative embeddings. Biometric verification was evaluated on the independent test set using exhaustive same-eye image pairing and cosine similarity. All image representations retained measurable subject-specific biometric signal. The full-fundus model achieved the highest performance (AUC, 0.992; EER, 4.4%), followed by the disc-region model (AUC, 0.989; EER, 5.5%) and the disc-only model (AUC, 0.969; EER, 10.5%). Accuracy was 0.968 for full fundus, 0.945 for disc region, and 0.919 for disc-only images. Pairwise comparisons showed significantly worse performance for disc-only images compared with full fundus (P < 0.001). Differences between full-fundus and disc-region models were small and not significant for AUC or EER. These findings demonstrate that deep learning models restricted to optic disc-centered fundus images retain meaningful subject-specific information, although performance declines as available retinal context is reduced. Inclusion of a narrow peripapillary rim yields biometric verification performance comparable to full-field fundus images. Although identity cannot be established from a fundus image without a linking key, recognizing that even restricted retinal regions retain subject-specific features highlights the importance of cautious data-sharing practices while supporting continued scientific collaboration.