Towards retinal membrane peeling with a handheld robotic instrument

Abstract

Vitreoretinal surgery procedures demand high precision and have to be performed with limited visualization and access. One such procedure is membrane peeling, which involves peeling of the 5-10 µm thick internal limiting membrane around macular holes. Robot-aided surgery has a lot of potential to improve the safety and accuracy of these procedures. Our goal is to develop a system for membrane peeling with the actuated handheld instrument Micron using virtual fixtures that works in-vivo. A cornerstone of many of the proposed virtual fixtures is reconstruction of the retinal surface with respect to the surgical tool, which is difficult to obtain due to the inadequacy of traditional stereo vision techniques in the intact eye. Instead, we aim to estimate the position of the retina in an intact eye by tracking a laser aiming beam interfaced with the Micron end-effector.

To move towards these goals, we develop virtual fixtures for membrane peeling and test their effectiveness with open-sky experiments in an artificial phantom. We find a significant reduction in the forces applied at the phantom during the robot-aided trials. To obtain an estimate of the retinal plane in-vivo, a structured-light technique using an aiming beam interfaced with the handheld instrument has been proposed, but it only provides a reconstruction at the start of the procedure; it cannot update it as the eye moves during surgery. We propose updating the initial estimate of the retinal plane a single point at a time, by continued detection of a laser aiming beam in each camera frame, as in the initial structured-light approach. The efficacy of this retinal plane update method is demonstrated by tracking a plane in an open-sky experiment and finding points on the plane in saline water.