Introduction: On November 21, 2025, the MDCG 2025-8  released its guidance on implementing the Master UDI-DI  for spectacle frames, lenses, and ready-to-wear reading glasses. This regulatory update, stemming from the EU MDR (Regulation 2017/745), is a game-changer for opticians. Starting now, professionals must prepare for its impact on traceability and Eudamed  registration. Here’s what you need to know. Why Does Master UDI-DI Matter? The Master UDI-DI  is a unique identifie