Automatic Instrument Tracking Endo-Illuminator for Intra-Ocular Surgeries1

Abstract

Vitreoretinal surgery encompasses intra-ocular surgical procedures performed in the posterior segment of the eye where instruments are inserted into the vitreous cavity to treat vision threatening diseases [1]. This surgery requires highly skilled surgeons to visually inspect and differentiate normal anatomy of the retina from pathology and manipulate retinal tissue with microsurgical instruments (Fig. 1Fig. 1Vitreoretinal surgery). Because the retina is on average 250 μm in thickness and retinal anatomical detail is microscopic, adequate illumination for a clear view of the retina during surgery is extremely crucial [1]. However, the current illumination solutions available require surgeons to devote one working hand to achieving suitable illumination.The traditional illumination option is a needlelike optic fiber enclosed by a rigid conduit, and is known as an endo-illuminator (Fig. 1) [1]. The surgeon views the surgery through a microscope with an optical path that passes through the lens of the patient's eye, while the light pipe is inserted via a small incision through the sclera. The light pipe provides a cone of illumination, where the angle of orientation and the proximity to the viewing surface can be controlled manually by the surgeon to achieve the desired lighting condition. Although this provides adequate lighting at all times, the surgeon has to devote one hand entirely for illumination, while performing surgery solely an end effector on the other hand (unimanual surgery) [1]. Instances exist when we prefer manual control of two end effectors (bimanual surgery). Alternative strategies of illumination, such as diffuse illumination or illuminated instruments, have thus far proved inadequate as they often create shadows or limited field of view, undermining the visibility and clarity of tasks performed during the operation [1,2].The superiority of bimanual surgery is evident in virtually all surgical fields and is ideal for implementation in vitreoretinal surgery [3]. Benefits include reduced surgery times, lower risks of complications, and faster learning curves for training surgeons. Additionally, bimanual techniques in vitreoretinal surgery allow the surgeon to externally depress the eye without the need of a trained assistant. Lastly, unimanual surgery is sometimes simply not an option. In highly complex cases commonly associated with diabetic patients, the procedure is far more challenging and habitually requires bimanual surgery in spite of currently available diminished lighting conditions [1].In this paper, we present a novel technology that makes an endo-illuminator “automatically” track the surgical instrument during operation to maintain the lighting quality (Fig. 2) [4]. This eliminates the need for the surgeon to hold and maneuver the endo-illuminator. As opposed to other extra-ocular robotic solutions that take up valuable space around the patient [5], we present an intra-ocular actuation approach that results in a novel, compact, and low cost system.Our approach, illustrated in Fig. 2, comprises an image recognition and processing module that uses a live video feed of the surgical feed from a microscope to locate and track the tip of the surgical instrument that is actively manipulated by the surgeon's primary hand; an intra-ocular actuation system that bends the flexible end of our proposed endo-illuminator such that it is always points at the instrument tip, based on the instrument tip location feedback received from the image processing module; and a holder that secures the rigid end of our proposed endo-illuminator in a fixed orientation during the surgery. These three modules are described in further detail below.Our proposed endo-illuminator closely resembles a regular endo-illuminator in size and shape (Fig. 3). However, a flexible portion, enclosing the optical fiber, is introduced at the distal end, which is actuated via three SMA wire loops that are symmetrically arranged around the flexible