2.6 Robotics

In vitreoretinal surgery, the manipulation of delicate tissues and structures requires a very precise positioning of instruments relative to their targets, often within about 10 microns.[1,2,3,4] This degree of precision is well below the 100 micron amplitude of the natural tremor present in a human hand.[5] Furthermore this surgery often requires certain static maneuvers, such as holding a cannula in a small structure (e.g. retinal vessel, sub-retinal space) without movement. Hence, a micro-manipulator or a robotic assistant can be of benefit to carry out high precision maneuvers with more ease and safety.

Robotic surgery took place as early as 1988 in the setting of stereotactic neurosurgery.[6] The first reported use of a micro-manipulator to facilitate retinal surgery occurred 5 years earlier in 1983.[7] The ongoing miniaturization of ophthalmic surgical instruments displaced the need for the micro-manipulator a few years later, and as a result, the drive to develop robotics in ophthalmology paused for several years.

The recent adoption of high precision imaging (e.g. intra-operative OCT, iOCT) in surgery and the need to carry out delicate site-specific procedures in the subretinal space (e.g. gene therapy) has reinitiated the interest for high precision robotics in our discipline.

Ophthalmic robots now in existence or in development can be classified into three main categories:[3,8,9]

All major features are summarized in Table 1

Table 1: Key Features and Properties of Ophthalmic Robotic Systems per Configuration

Assistive hand‑held instruments are special tools that aim to compensate for tremor and unintentional movements in the surgeon’s hand.[10] The surgical instrument is mounted on a hand‑held compensating device that stabilizes and cancels out unwanted fine movements (Figure 2.6.1).

A co-manipulation system uses a mechanism designed to facilitate specific surgical tasks. It can, for example, stably hold an instrument (catheter) in a vessel, for a prolonged period of time. During a surgical maneuver, the manipulator dampens movements, thereby limiting tremor. It can also maintain a stable position independent of the surgeon’s grip, further extending the physiologic reach of a surgeon.[11,12,13] Co-manipulation avoids the need for a separate joystick, or the need for a sophisticated computerized control mechanism, reducing the cost of the system . However, it comes at the cost of limited flexibility, dampening and hindering the movement of the surgeon’s intraocular movements (Figure 2.6.2).

Tele‑manipulation systems, are based on the so-called “master-slave” design. The surgeon controls at a distance, a robotic manipulator to which instruments can be attached and used to perform surgical maneuvers and tasks. The surgeon interacts with the manipulator through a motion controller. The controller can be operated by the surgeon either positioned adjacent to the surgical site or at a console (decoupling the surgeon from the patient and the surgical field). Depending on the level of precision needed (controlling ocular and/or patient head movements), chandelier intraocular illumination and/or a dedicated head stabilization or head positioning device may also be required. Motions generated by the controller are fed to a computer that translates and adapts the movement to the robotic arm as a function of the required (intraocular) task. Robotic functionalities such as standby, stored position and advancement bounds are benefits of tele‑operation systems which allow the surgeon to maintain a precise overview and control of movement within the surgical field. Surgical visualization (using current imaging systems) is unchanged, using the oculars of a microscope or digital 3D on an external monitor (Figure 2.6.3).

The Preceyes Robotic Surgical System (PRSS) is a telemetric system that has received CE mark approval for use in the vitreo-retinal surgical environment without any limitation to a specific task. Several different intraocular instruments can be fitted to the PSS and are approved for use, increasing the versatility of the platform. Interaction with iOCT and, in the future, OCT probes that are integrated into the tip of instruments will further advance high precision imaging and permit instrument movement boundaries in real time.