This study is the first to apply RETFound, a baseline model for existing fundus camera and optical coherence tomography images, to the task of optical disc segmentation. By training a new head with only a small amount of task-specific data, we achieve performance (approximately 96% Dice coefficient) that outperforms state-of-the-art segmentation-specific baseline networks on several public datasets (IDRID, Drishti-GS, RIM-ONE-r3, REFUGE) and a private dataset (GoDARTS). The baseline model demonstrates superior performance in internal validation, domain generalization, and domain adaptation, demonstrating its potential as an alternative to task-specific architectures.