Force sensing micro-forceps for robot assisted retinal surgery

Abstract

Membrane peeling is a standard vitreoretinal procedure, where the surgeon delaminates a very thin membrane from retina surface using surgical picks and forceps. This requires extremely delicate manipulation of the retinal tissue. Applying excessive forces during the surgery can cause serious complications leading to vision loss. For successful membrane peeling, most of the applied forces need to be very small, well below the human tactile sensation threshold. In this paper, we present a robotic system that combines a force sensing forceps tool and a cooperatively-controlled surgical robot. This combination allows us to measure the forces directly at the tool tip and use this information for limiting the applied forces on the retina. This may prevent many iatrogenic injuries and allow safer maneuvers during vitreoretinal procedures. We show that our system can successfully eliminate hand-tremor and excessive forces in membrane peeling experiments on the inner shell membrane of a chicken embryo.

Figure 1

1: The graspers of 23Ga disposable forceps, 2:Nitinol tube with FBGs, 3: Easy-release mechanism, 4: Optical fibers, 5: Handle of the disposable forceps, 6: Original 23Ga disposable forceps (Alcon, USA).

Figure 2

The force sensing module and its fabrication steps. First, three half tubes were located on the nitinol tube (upper). Second, FBGs were inserted through half tubes to achieve axi-symmetric configuration (lower).

Figure 3

Squeezing the handle slides the actuation tube (green) in distal direction and closes the graspers (blue).

Figure 4

The graspers (blue) and the actuation tube (green) can be rotated together in the nitinol tube (red) by rotating the handle.

Figure 5

Calibration results in x-axis direction (left) and in y-axis direction (right). Linear behavior is observed for all FBGs in both axes.

Figure 6

Setup for membrane peeling experiments on inner shell membrane in chicken embryo.

Figure 7

Membrane peeling forces on chicken embryo from a test sample: (a) completely unaided, (b) robot assisted with only auditory force feedback, (c) robot assisted with only force scaling, (d) robot assisted with auditory force feedback and force scaling. High frequency oscillations in delaminating forces are reduced by steady-hand robot. Force scaling provides smoother force variations. Auditory feedback is beneficial for keeping the forces within the safe operation zone (red lines).