Vitrectomy cutters are the fundamental tool for vitreoretinal surgeons. South Australian retinal specialist DR STEWART LAKE discusses one of the latest advances in the field and how it’s leading to safer, more efficient surgeries.
Since vitrectomy cutters were pioneered in the 1970s, manufacturers have sought to improve their safety and efficiency with smaller gauge size and increased cutting speeds, while also attempting to maintain consistent flow rates. Other components such as the port geometry and blade design have also undergone significant modifications.
This tricky balancing act is one that South Australian ophthalmologist Dr Stewart Lake has followed closely over his near-two-decade career as a vitreoretinal surgeon with a keen interest in new surgical technology.
Lake, who splits his time between public work at Flinders Medical Centre and privately at the three-site practice Eyemedics, says vitrectomy cutters have advanced significantly over time. Now, surgeons can perform vitrectomies with more precision, predictability and efficiency.
Vitrectomy involves removing the vitreous humour to allow surgeons to perform other procedures that cannot be done with the fluid vitreous in its place. The clear jelly-like substance is composed of more than 99% water, as well as collagen fibres, proteins and hyaluronan.
In the early part of his career, Lake recalls vitrectomy cutters were 20-gauge, with the larger incisions requiring sutures, leading to slower recovery and more postoperative pain. Over time, instrument size reduced to 23, 25 and 27 gauge, with some early trade-off in the rigidity of the cutter, making them more difficult to control.
“In recent years however, the instrumentation has improved in two areas, the smaller gauge instruments have improved in their rigidity making them more acceptable, and manufacturers have increased the cut rates to help reduce tissue handling issues including traction on the retina,” he says.
Conventional systems have largely featured a single opening cutter design that cuts in one direction. Although surgeons have welcomed increased cutting speeds to allow for more precision – particularly when shaving near the retina – this can somewhat paradoxically lead to slower overall operating times due to slower flow rates to remove the vitreous. In other words, the aspiration port isn’t open for as long.
“So, the aim has been to make the gauge smaller, increase the cut rate to reduce the chance of complications, but also maintain the flow rate so that you are not slowing down the operation time,” Lake says, noting that longer surgical times can lead to patient discomfort and affect visualisation, while also increasing the risk of a complication occurring.
Adopting a system that addresses these key issues was the impetus for Flinders Medical Centre to acquire the latest in vitrectomy cutting technology from Bausch + Lomb (B+L).
Last year, the hospital added the Bi-Blade dual port vitrectomy cutter to its two existing Stellaris Elite vision enhancement systems, allowing Lake and his colleagues to perform more predictable and efficient vitrectomies on their patients. At Flinders Medical Centre, these include Indigenous patients flown in from the Northern Territory for retinal surgery, many with complex diabetic eye disease.
According to B+L, the Bi-Blade – available in 27, 25 and more recently 23 gauges – is a significant advance over conventional cutters. While single-port cutters cut only in the forward direction, the Bi-Blade’s dual-edge blade cuts in both the forward and backward directions, performing two cuts per cycle.
This offers an effective 15,000 cuts per minute (cpm) rate.
The design also means cutting is performed with less port closure time, allowing the system to provide more continuous aspiration. This ultimately results in increased flow efficiency and control compared to prior generation guillotine cutters, B+L states.
“Previously, with the traditional technology, we used a cutter that had a single opening and as the cut rates increased, this also meant the port was closed for a slightly greater proportion of the cycle,” Lake says.
“But the design of the Bi-Blade essentially has two openings, or two blades, so for each cycle you get double the number of cuts. That maintains higher opening time, which maintains flow, and improves the efficiency of the surgery, but also keeps traction low by not dragging hard on the retina.”
With conventional cutters, Lake says he was more previously inclined to opt for the larger 23 gauge, only using 25 sparingly. However, he believes the 25-gauge Bi-Blade performance in terms of efficiency and rigidity is superior to the 23-gauge single port cutter.
Using a smaller gauge is better for several reasons, the obvious being the smaller incision. Although surgeons perform self-sealing pars plana sclerotomies to prevent leakage, wound healing involves vitreous incarceration (where vitreous is trapped within a wound or incision site), which can lead to discomfort and affect vision.
“With a smaller gauge, we have a smaller opening, which means faster healing, therefore the patient has less hypotony when the eye is soft, and therefore faster recovery,” he explains.
Further, in patients with diabetic eye disease with fibrotic bands, he says the smaller gauge allows the surgeon to tunnel in and trim closer to the retina. It has other advantages in cases that require shaving at the vitreous base – an area of strong adhesion where in the past surgeons needed to limit traction on the retina by using lower aspiration rates.
“When you’re shaving at the vitreous base, with older cutters, you are having to do other things to make the system safer that make it less efficient. This is usually done by dropping the vacuum – you still want to go close to retina, but to do that safely with a non-Bi-Blade system, you have to reduce aspiration so you are putting less force on the retina. However, if you’re reducing aspiration you are effectively being less productive compared to a Bi-Blade cutter where you can cut more efficiently close to the retina.”
Additionally, in retinal detachments, he says the rigidity of the Bi-Blade – even in smaller gauges – allows for more controlled access to the peripheral retina towards the front of the eye.
“Then in the opposite direction, where you’re working on the back of the eye for conditions such as macula holes or epiretinal membranes, or more severe diabetic eye diseases, it gives you that nice efficient, stable system, so it works well in both settings.”
An innovative foot pedal
B+L’s Bi-Blade procedure packs are exclusive to its latest vision enhancement system called the Stellaris Elite. Flinders Medical Centre have had the system installed before introducing the Bi-Blade, so it was a relatively minor adjustment to the operating room, requiring a minimal learning curve.
The Stellaris Elite is a combined surgical platform, which offers both cataract and retina capabilities.
Lake says a key feature of the platform is what B+L calls a dual linear foot pedal, which is unique. When performing a vitrectomy, he says it allows him to independently adjust both the aspiration and cutting rates with his foot, without having to move away for manual adjustments. Other systems have less flexibility in control.
“The Stellaris offers full dual linear capabilities, where you have dual, simultaneous, independent control of vacuum and cut rate. I can move the foot pedal up and down to control one, and then side-to-side to control the other,” he says.
“It means I can increase the suction rate and keep the cut rate low, or vice versa – that is quite a major advance for several different conditions, particularly macula holes where you want to aspirate without cutting to pull the posterior vitreous off the retina, whereas with other machines you have to keep kicking the cut rate on and off.
“With diabetic eye disease it’s also ideal because you’d want a high cut rate and low suction – because you want to shave and not consume a lot of tissue – the foot pedal makes this easy to control.”
The Stellaris Elite system also has colour filters (yellow, green and amber) that can be used as augmentation or an alternative to intraoperative dyes.
Although he only uses this occasionally, Lake says it’s nice to have up his sleeve for macula work by helping to visualise the vitreous and scar tissue, as well as while performing epiretinal membrane peels.
While the Bi-Blade is B+L’s most advanced vitrectomy cutter in Australia, the company is poised to launch a new generation vitrector called the Vitesse hypersonic vitrectomy system.
Lake is among a handful of surgeons trialling the device globally, which uses an ultrasonic vitrectomy probe to liquefy and then aspirate vitreous at the edge of the port. Without a guillotine-like mechanism, this also means its port is open 100% of the time.
“It’s exciting technology, and globally surgeons are helping to explore and optimise the settings to make it work most efficiently,” Lake adds.