The integration of robotics into retinal microsurgery leads to a reduction in surgeon perception of tool-to-tissue interaction forces. This blunting of human tactile sensory input is due to the inflexible mass and large inertia of the robotic arm as compared to the milli-Newton scale of the interaction forces encountered during ophthalmic surgery. The loss of human tactile feedback, as well as the comparatively high forces that are potentially imparted to the fragile tissues of the eye, identify a potential iatrogenic risk during robotic eye surgery.
In this paper, we aim to evaluate two variants of an adaptive force control scheme implemented on the Steady-Hand Eye Robot (SHER) that are intended to mitigate the risk of unsafe scleral forces. The adaptive control methods make the robot to autonomously reduce the scleral forces based on desired pre-defined trajectories in case they overstep safe limits. The present study enrolled ten retina fellows and ophthalmology residents into a simulated procedure, which simply asked the trainees to follow retinal vessels in a model retina surgery environment, with and without robotic assistance. For this purpose, we have developed a force-sensing (equipped with Fiber Bragg Grating sensors (FBG)) instrument to attach to the robot. A piezo-actuated linear stage for creating random lateral motions to the eyeball phantom has been provided to simulate disturbances during surgery. The SHER and all of its dependencies were set up in an operating room in the Wilmer Eye Institute at the Johns Hopkins Hospital. The clinicians conducted robot-assisted experiments with the adaptive controls incorporated as well as freehand manipulations. The results indicate that the Adaptive Norm Control (ANC) method, can maintain scleral forces at predetermined safe levels better than even freehand manipulations.