FBG-Based Transverse and Axial Force-Sensing Micro-Forceps for Retinal Microsurgery

Retinal microsurgery routinely requires the manipulation of extremely delicate tissues. Membrane peeling is a prototypical task where a layer of fibrous tissue is delaminated off the retina with a micro-forceps by applying very fine forces that are mostly imperceptible to the surgeon. Previously we developed sensitized ophthalmic surgery tools that can precisely detect the transverse forces at the instrument's tip via integrated fiber Bragg grating strain sensors. This paper presents a new design that employs an additional sensor to capture also the tensile force along the tool axis which can be significant in membrane peeling. We investigate two distinct fitting methods to compute the transverse and axial forces based on sensor outputs. Validation with random samples shows that the linear method closely predicts the transverse force but does not provide sufficient accuracy in computing the axial load. Our nonlinear method resolves this problem, providing a more consistent and accurate measurement of both the transverse and axial forces.