Adaptive Control Improves Sclera Force Safety in Robot-Assisted Eye Surgery: A Clinical Study.

The integration of robotics into retinal microsurgery leads to a reduction in surgeon perception of tool-to-tissue interaction forces. Tool shaft-to-sclera, and tool tip-to-surgical target, forces are rendered either markedly reduced or imperceptible to the surgeon. 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 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. The study was approved by the Johns Hopkins University Institutional Review Board. For this purpose, we have developed a force-sensing (equipped with Fiber Bragg Grating (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, is able to maintain scleral forces at predetermined safe levels better than even freehand manipulations. Novice clinicians in robot training however, subjectively preferred freehand maneuvers over robotic manipulations. Clinician preferences once highly skilled with the robot is not assessed in this study.