Force Perception Instrument for Robotic Flexible Micro-Catheter Delivery in Glaucoma Surgery

Glaucoma ranks the first in the worldwide irreversible eye disease, characterized by the elevated intraocular pressure and damage to the optic nerve, or permanent blindness. The micro-catheter delivery of transluminal trabeculotomy under gonioscope is a novel non-follicular-dependent anti-glaucoma surgery with less trauma and blood loss. However, the manual operation is not easy, the flexible micro-catheter with 220
$\mu \mathrm{m}$
diameter easily got lost, or broke off when manipulated by the micro-tweezers for several times. Therefore, a robotic flexible micro-catheter delivery instrument with pre-bent configuration is proposed, of which the axial force is simultaneously measured. The geometric mapping relationship between the confined intra-luminal space and a mechanically constrained fixed point was established. The kinematic constraint is constructed where the distal belt end of the instrument should keep tangent to the Schlemm's canal (SC) entry point for smooth delivery. In vitro experimental studies on isolated pig eyeballs, the results show that the average traveling force of the isolated pig eyeball is approximately 136 mN, with maximum 272 mN, and the average delivery distance is about 8 mm. This work provides a novel instrument for the micro-catheter delivery of 360° trabeculotomy for glaucoma surgery, which can be installed on the robot body and operated by a manipulator (Omega 7) for surgeons. It can be used to reduce the operation difficulty and perform better than the existing methods in enhancing the operational skills of surgeons.