Improvements To A Robotic Arm Setup For Anterior Eye Surgery

While the usage of robotic arms to assist or perform surgeries is already established in many medical sectors, it is still in a state of early research in ophthalmology. This is due to special challanges in this field such as high precision requirements and a moving target structure. Further more a lot of ophthalmic procedures (e.g. cataract surgery) require an sizable array of highly specialized instruments. We updated our experimental robotic setup with the goal to address these challenges.

Our experimental robotic surgery setup, as described earlier [Investigative Ophthalmology & Visual Science, June 2023, Vol. 64, 3328], was used. Key elements are an robotic arm (Universal Robots UR3e) and a custom 3D camera with an integrated light source required for the red reflex. The 3D camera replaces the traditional microscope, providing visual feedback for the operator as well as 3D telemetry data (using triangulation) required to guide the robotic arm.

A revolver style instrument changer was developed, that is mounted to the robotic arm and holds the various instruments required for the procedure at hand. Currently the semicircular storage can hold 5 instruments mounted to linear runner blocks. The storage can be rotated to align the desired instrument with a linear rail that transports the instrument to the working position. Further the 3D camera was improved by adding the ability to automatically adjust the focus. This is achieved by moving the stereo camera setup vertically using a precision linear stage, shifting the object plane. Feedback from the stage is used during the triangulation to receive accurate results independent of the stages current position.

Adapter pieces allow the usage of commercially available instruments as well as instruments specialized for the use with a robotic system. The instruments are easy to mount into the storage positions. The 3D camera is used to check and account for the actual position of the instrument tip when it is in the working position. This is necessary because of small inconsistencies within  the individual instruments of the same batch, as well as the possibility of slightly bent tips. The updated 3D camera manages to automatically keep the desired structures in focus while maintaining its previous triangulation accuracy.

The revolver style instrument changer allows the robot to switch between the different surgical instruments needed during the procedure without the need to move away from the patient or manually mounting a different instrument to the arm. The ability to retract the instrument using the linear rail, without relying on motions of the actual robot arm, is another benefit of this construction. In an emergency situation the position of the arm can be frozen and the instrument can be extracted from the eye in a linear motion. 
The autofocus ability of the stereo camera is an essential addition to the setup.