Cutting tool for cataract surgery

A new circular cutting tool will make cataract surgery an easier process for doctors, according to its developers.

The device from Warwickshire-based Warwick Design uses a circular superelastic nickel-titanium blade to cut an opening in the anterior of the capsule, a cellophane-like part of the eye that retains the failing lens. Current blades require surgeons to tear a circular hole, a skilled procedure that can lead to serious consequences if performed incorrectly.

The Warwick Design device does not require such tearing and therefore reduces the necessary skill level and the failure rate of this procedure.

All cataract operations require a small 2.8mm incision in the edge of the cornea to get the instrument in place to cut the hole. When the hole is cut, the old lens is broken apart with an ultrasonic probe, sucked out with a vacuum and replaced with a plastic lens, which is folded up and inserted through the cornea incision.

The circular blade instrument was conceived by John Stokes, a UK ophthalmic consultant at Nottingham University Hospitals NHS Trust. The NHS Innovation East Midlands approached Warwick Design to turn the idea into a practical instrument.

The lead developer of the device, Andrew Gibbs, design manager at Warwick Design, said others have tried creating such a circular blade before but none came to fruition.

’They were patented ideas but they were not actually manufactureable,’ he added. ’There were no processes that could achieve those designs.’

Achieving the right design was no easy task. Gibbs said it was difficult to decide on the right kind of material for the blade, and his team had to prove the blade was small and workable enough to carry out a variety of tasks in a tight space. The blade has to be deployed through a 2mm diameter plastic tube inserted in the cornea incision.

’If you can imagine not only working through a tiny incision but also tearing a perfectly round circle of well-controlled dimension —probably plus or minus a quarter of a centimetre in cellophane — is very tricky,’ he added. ’This situation is much worse in paediatric eyes, particularly under the age of two years, because the eye capsule is very elastic and not only is the hole to be torn smaller, but also the tear wants to run radially outwards in preference to going round. There is no natural grain that gives you a circular tear.’

The Warwick Design team decided upon nickel-titanium superelastic alloy, because of its ability to bend without non-elastic deformation. The team also determined a blade made of such material would have sufficient sharpness to take and maintain a cutting edge.

Gibbs said the team started modelling the device using CAD program Pro/Engineer.

’Obviously this is a moving device so we had to model it in various states of deformation and there are some complex challenges there even with a competent software like Pro/E,’ he added.

Warwick Design worked with Richard Allan Medical, a Redditch, Worcestershire-based manufacturer of medical products, to micro-manufacture the initial blades. Warwick Design developed the plastic mouldings. A working model of the device was tested on porcine eyes.

The Wellcome Trust has recognised the potential of the instrument and is providing around £300,000 of funding to help make it viable for manufacture.

’There is the challenge of making these devices at a reasonable cost because at the moment the tools to do tearing procedures are relatively low cost,’ said Gibbs.

’However, the combination of training and complications with that procedure puts that cost up.’

Gibbs hopes his team will perfect the tool for both adult and paediatric use in the next two-and-a-half years. ’We’re already getting interest from a number of companies,’ he said.

Gibbs predicted such devices could be used in hospitals for cataract surgeries within five years.

Siobhan Wagner