A Shared Control Architecture for Vitreoretinal Surgery With Safety Guarantee Using Control Barrier Functions

Control Barrier Functions (CBFs) provide a powerful framework for enforcing real-time safety in control systems and have seen increasing applications in safety-critical domains, such as surgical robotics. In vitreoretinal microsurgery, where precision and tissue protection are crucial, we propose a shared control approach that leverages CBFs to maintain the robot's end-effector within a safe zone above the retina. Using real-time 3D reconstruction from an instrument-integrated Optical Coherence Tomography (iiOCT) system mounted on the surgical tool, we define a safety band between two offset surfaces derived from the reconstructed retina. A hybrid controller drives the tool into the band when outside and then enforces forward invariance using a CBF-based quadratic program. Concurrently, haptic feedback proportional to the deviation from the band centre guides the surgeon toward the optimal working distance. We validate our method in ex vivo pig eye experiments, performing a simulated Vitreous Shaving (VS), showing improved safety and operator awareness.