Miniature robot surgeons prepare for cataract surgery

Cambridge Consultants have shown that the procedure to perform cataract surgery could soon be carried out robotically. Helen Knight reports

Cataract surgery is the most commonly performed procedure in the world, restoring sight to 20 million people each year.

But the procedure is currently performed by hand, using a pair of surgical tweezers and a microscope. This can result in complications, as the delicate nature of the surface of the eye means it can be easily damaged.

Now engineers at product design firm Cambridge Consultants have shown that the procedure could soon be carried out robotically, thanks to the development of one of the smallest known surgical robots.

Axsis, developed by the company’s engineers to demonstrate the technology’s potential, has a body the size of a soft drinks can, and can manipulate surgical instruments of 1.8mm in diameter.

As well as performing cataract and other forms of eye surgery, the robot could also be used for other minimally invasive procedures, such as implanting neurostimulation devices, early cancer intervention, and oesophageal and gastrointestinal tract operations.

Existing surgical robots are typically large devices, since they have to control long, straight instruments that must be fed through small holes in the patient, necessitating a large range of motion on the outside of the body, said Chris Wagner, head of advanced surgical systems at Cambridge Consultants.

In comparison, Axsis can manipulate tiny, flexible instruments. “Right now [surgical robots] can handle arteries and blood vessels, but we want to move to the next generation, where they can handle fine nerves and even finer blood vessels,” said Wagner.

The robot’s instruments are controlled by an actuator consisting of a channel surrounded by four high strength mechanical cables.

“We have high strength cable running through guide channels, which go up through a series of rolling metal link mechanisms out to the end, where the grasper is located,” said Wagner.

The 110μm cables each run through 150μm guide holes. Depending on which of the cables is pulled, the instrument can be moved, up, down, left or right.

“The cables provide tension and articulating force,” he said.

In order to ensure the robot could be kept as small as possible, the engineers designed the articulating mechanism to be as efficient as possible, in order to minimise frictional losses. In this way they were able to reduce the size of the motors needed to drive the cables, said Wagner.

This high efficiency also allows the device to relay forces encountered by the tips of the instruments back to the actuator, meaning it can be used to provide feedback.

“The forces that are encountered by the tip are transmitted up through the cable into the actuator,” said Wagner. “So let’s say the actuator [attempts to] go to position five, but it only achieves position six. That means I know there is a force pushing against the tip, and that force isn’t coming from anywhere else like friction losses,” he said.

This means that any forces interacting with the tips of the instrument can be felt by the surgeon operating the device, giving them a sense of touch.

Depending on the design of the instruments used, the robot could allow the size of the minimally invasive access point on the patient’s body to be reduced.

Smaller robots also mean surgeons could ultimately work with a range of tools, and get closer to the patient without large equipment getting in their way.

The reduction in size should also lead to cost savings, and allow the device to be used by smaller hospitals, expanding the number of facilities that can offer such procedures.