Hypersonic vitreous liquefaction drives breakthrough innovation in vitrectomy

Hypersonic vitrectomy, which uses hypersonic reciprocating hydraulics to liquefy the vitreous, may be the next major breakthrough in vitreoretinal surgery. While pneumatic cutters use a double-port probe, wherein the vitreous is first aspirated and then sheared, the new system liquefies and aspirates the vitreous with a 23-gauge single-port probe.

“Rather than being cut, the vitreous is reduced to the viscosity of water and aspirated, using much lower energy with greater efficiency, causing less traction and turbulence,” Amar Agarwal, MS, FRCS, FRCOphth, director of Dr. Agarwal’s Group of Eye Hospitals, said.

In addition, Agarwal expects the same probe can be used for both cataract surgery and vitrectomy in specific cases to remove nuclear fragments and vitreous in posterior capsular rupture.

“This is a huge advantage,” Agarwal said.

Source: Anusha Venkataraman, MD, FRCS(Glasg), FICO

The Vitesse hypersonic vitrectomy system is exclusive to the Stellaris Elite dual-function cataract and vitrectomy platform (Bausch + Lomb). The unit has the capability to drive the Vitesse handpiece; once activated, the software allows the handpiece to be controlled via the foot pedal and the console screen.

In April 2017, the system was granted 510(k) FDA clearance, and in January 2018, the system received a CE mark in Europe.

The first human case was performed in Chennai, India, at Dr. Agarwal’s Eye Hospital, and the first 20 cases operated there by Paulo Stanga, MD, Agarwal and Anusha Venkataraman, MD, FRCS(Glasg), FICO, head of Dr. Agarwal’s Retina Foundation, were included in a pilot study.

The results of the study have not yet been disclosed, but Dhivya Ashok Kumar, MD, FICO, research officer of the project, said that surgery was mostly uneventful and patients are doing well.

“I was there during surgery and was impressed by the fast cutting speed and the consistent flow and aspiration that provided excellent control during surgery. It is very safe, and whatever minimal complications happen during surgery could happen with any vitrectomy procedure; there is nothing that could be attributed to the device itself,” she said.

Patients with a variety of conditions were recruited, including vitreous hemorrhage, macular hole, epiretinal membrane and asteroid hyalosis. Two additional cases were treated later, including one case of retinal detachment.

“This was only a preliminary study with a narrow group of patients, and we need to extend our experience to various indications like fibrous band, dense vitreous and also young patients to see if we can cut the vitreous as well as we do in elderly patients. We need more cases to analyze the functional and anatomic results. Theoretically, there is no contraindication for this new method,” Kumar said.

Liquefaction and aspiration

The Vitesse system utilizes a frequency of 28.7 kHz and a stroke length of 0 µm to 60 µm. The 23-gauge, 33-mm-long stainless-steel needle oscillates with user-controlled amplitude, liquefying the tissue in a highly localized zone at the edge of the port.

“The vitreous is made of water and collagen, and what the system does is turn collagen fibrils into liquid,” Agarwal said.

Conventional guillotine vitrectomy probes consist of a hollow inner tube surrounded by a hollow outer tube arranged coaxially. Vitreous is drawn by aspiration into a port near the distal end of the outer tube. Then the inner tube slides forward, closing the port and shearing off the vitreous. The cut material is aspirated out of the eye through the inner tube.

“The new-generation 20-, 23- and 25-gauge cutters achieve high vitreous flow rates, but the periodic opening and closing of the port generates turbulence. Although increasing the cut rate may reduce this turbulence, any cutter with a periodically closed port will result in this effect,” Agarwal said.

In addition, vitreous material may be caught between the inner needle and the port edges. If the outer needle port is not large enough to allow a reasonable amount of tissue to enter and be cut, the vitreous may be aspirated uncut, or partially cut, through the port, resulting in direct traction on the vitreous strands. The hypersonic vitrector has a single needle instead of two needles, so there is no chance of trapping vitreous strands between the port edge and the needle. The port is continuously open, allowing smaller port sizes and larger inner-lumen diameters, which in turn lowers flow resistance and infusion pressures.

Safe for the retina

“During conventional vitrectomy, aspiration and cutting cause a lot of traction on the retina. Hypersonic vitrectomy liquefies the vitreous at the port, does not cause any traction and after liquefaction it aspirates the vitreous. That means that there is no active pulling, no traction of the retina and the chances of complications are much less,” Venkataraman said.

She found that during surgery the probe worked well and it was easier to use than a pneumatic cutter.

“We could go very close to the retina and in certain cases even closer than we would with a pneumatic cutter. We could easily and safely shave the vitreous base, and there was no traction on the retina. The surgery was pretty smooth,” she said.

Venkataraman performed the first case of retinal detachment using the hypersonic vitrector. Surgery was carried out safely, and the patient’s vision improved from 20/200 to 20/30.

“The retina is well attached, and the vitreous was effectively and thoroughly removed,” she said.

New-generation pneumatic cutters have an increased cut rate, but the highest speed is currently around 5,000 to 7,500 cuts per minute. On the other hand, the speed of the hypersonic vitrector is around 1.7 million cuts per minute.

“That is really a huge difference, which explains why the efficiency is much better,” Venkataraman said.

The hypersonic vitrectomy technology has evolved through several prototypes to improve efficiency and minimize the impact of acoustic radiation on the retina.

“With the current platform, the procedure is safe and no damage is caused to the retinal pigment epithelium (RPE),” she said, because of the constant fluid circulation and lesser stroke being used.

One of the patients operated on at Dr. Agarwal’s hospital had retinal detachment, but this was due to the patient’s underlying conditions and not to the surgery.

“There was no case of RPE damage, no visual loss and no postoperative complication attributable to hypersonic vitrectomy. In terms of efficacy and safety, this system is superior to pneumatic cutters,” Venkataraman said.

Experience in United States

Since the initial cases in India, surgeons have performed several operations in the United States. Kevin J. Blinder, MD, has treated approximately 30 patients at The Retina Institute in St. Louis.

“My experience began in the lab a few years ago with the first prototype. After many pig eyes and multiple revisions of the probe, Bausch + Lomb obtained FDA approval for the present-day Vitesse probe,” he said.

Blinder explained that the high hydraulic velocity creates cyclical stresses of shear cross-flow and elongation of the vitreous — disrupting or liquefying it.

“This is very different from the standard pneumatic cutter that we presently use. The port is continuously open, so we do not have to think about a duty cycle. The tissue disruption occurs in front of the port opening, and the port size can be smaller than what we have previously seen with the pneumatic cutters. The Vitesse probe is a single tube, thus simplifying the design and complexity of the inner and outer tube of the pneumatic cutters,” he said.

He believes that hypersonic vitrectomy will gain fast and wide popularity among surgeons once it becomes available. However, because it is a completely new way of removing the vitreous, there is a learning curve for using and understanding the technology.

“There is great potential with Vitesse, and I think many of our colleagues will be excited to try it and integrate it into their OR regimen. It is not difficult to use, but it functions very differently than the traditional pneumatic cutter. I have done a wide range of cases from simple floaterectomies to complicated retinal detachments with proliferative vitreoretinopathy, and so far, I have not had to convert to the traditional pneumatic cutter in any cases,” Blinder said.

Optimizing parameters

Carl C. Awh, MD, president of Tennessee Retina in Nashville, was also involved in the development of the Vitesse technology.

“[Bausch + Lomb] asked me, along with a few other surgeons, to assist in the evaluation and development of this new technology. Our initial observations in the laboratory convinced us that the technology would allow us to effectively remove vitreous and cut membranes. Our work in animal eyes demonstrated that hypersonic vitrectomy does not cause unintended damage or toxicity to intraocular structures. These experiences led to refinements in the design of the port and development of appropriate parameters for the device that we have now successfully used in humans,” he said.

To date, Awh has performed more than 30 cases in humans, addressing a wide range of typical surgical pathology, including epiretinal membrane, macular hole, rhegmatogenous retinal detachment, tractional retinal detachment, vitreomacular traction, and retained silicone oil or lens cortex material.

“We are still learning how to optimize the relationship between vacuum and stroke, ie, the amount of oscillation of the probe. I approach each case with particular caution and take my time to make deliberate adjustments in these parameters. I have become more and more comfortable working near mobile retina and the macular surface, and have not had to switch from the Vitesse to a conventional vitrectomy cutter during a single case,” he said.

Awh has encountered two complications: a retinal break in a detached retina and pitting of an IOL during posterior capsulotomy. In both cases, he realized the stroke setting was too high.

“In theory, we may be able to remove vitreous or other tissues with less traction than with a guillotine-type cutter. Initial surgical experience shows that we can effectively remove vitreous at lower levels of vacuum and infusion pressure than with pneumatic guillotine cutters, which may also prove to have advantages. It is too early to say whether this is a superior way of disrupting tissues, but our initial experience has been compelling,” Awh said.

Flow characteristics are also improved because, with no inner guillotine sleeve, the lumen of the cutter is larger.

“We’ve shown that we can remove large amounts of 5,000 centistoke silicone oil using the hypersonic vitrector, which clearly demonstrates that the mechanical effect of this technology is quite different from that of guillotine cutters,” he said.

Managing cataract surgery complications

Intraoperative posterior capsular rupture leading to vitreous loss into the anterior chamber can occur in complicated cataract surgeries. The vitreous gel has the property to enmesh and create significant entanglement with the structures it comes into contact with. The residual vitreous prevents IOL placement and causes significant postoperative complications such as macular edema, retinal traction, abnormal pupil and glaucoma. Hence, removal of vitreous from the anterior chamber and the pupillary plane is the initial step after any intraoperative posterior capsular rupture.

Hypersonic vitrectomy can make this less complicated for the surgeon because the probe can remove both the vitreous and the nuclear fragments.

“What we can do is bring the nuclear fragments above the iris and then place under the fragments a three-piece IOL, which acts as a scaffold. At this point, we can easily remove the fragments with the hypersonic probe and finally glue the three-piece IOL into the sclera using the glued IOL technique,” Agarwal said.

One case Blinder found particularly interesting was an elderly woman with a dense counting fingers cataract. The anterior segment surgeon had a difficult time intraoperatively with phacoemulsification, and a large piece of the nucleus went into the vitreous cavity.

“I brought the patient back to the operating room a few days later. Utilizing the Vitesse technology, I performed a 23-gauge three-port pars plana vitrectomy. I was able to remove the dense nuclear remnant and residual cortical material with the Vitesse alone, without necessitating the use of the fragmatome. By utilizing the hypersonic vitrector, I did not have to remove the cannula as you do when using the fragmatome. This also decreases the rate of iatrogenic peripheral retinal tears that can occur with the fragmatome. The patient tolerated the procedure well and is back in the capable hands of the anterior segment surgeon,” he said.

Future improvements

As for any new technology, there are a few potential drawbacks to the system, according to Blinder. As previously mentioned, there is a learning curve that the surgeon must be willing to experience. But the main limitation currently is the 23-gauge size of the probe.

“For those surgeons who prefer 25- or even 27-gauge surgery, this will be taking a small step back. However, think of the first-generation pneumatic cutters. We have come a long way since 17-gauge vitrectomy. I think the potential for further innovation with the Vitesse is great. With a single-tube design, 27 or even 29 gauge seems feasible,” he said.

“It is very difficult to incorporate two tubes in the same gauge, but the hypersonic vitrector has one tube, and this makes it easy to reduce the size of the instrument. In the future, we will be able to use smaller-gauge instruments and the efficacy might be much better than with conventional small-gauge cutters. One tube is easy to manipulate, modify and make surgeon-compatible,” Venkataraman said.

Ther hypersonic action poses no limitation to the shape of the probe, and a curved probe, easier to use toward the periphery, is a possible new design for the future, according to Agarwal.

“The R&D team at Bausch + Lomb has done a wonderful job thus far and is forging forward with future innovations. A curved probe is possible with a single-tube design, which would have certain advantages in phakic patients,” Blinder said.

Whether hypersonic vitrectomy will prove superior to conventional pneumatic guillotine vitrectomy remains to be seen because experience so far is too limited to make a fair judgment, Awh said.

“However, what we’ve accomplished thus far is promising, and I think that continued advancements in probe design and optimization of device settings may allow us to expand the range of techniques we currently perform with conventional technology,” he said. – by Michela Cimberle

Editor’s note: Please see the video blog of Priya Narang, MS, posted Dec. 8, 2017, on Healio.com/OSN, which demonstrates the hypersonic vitrectomy procedure.

• References:
• Pastor-Idoate S, et al. PLoS One. 2017;doi:10.1371/journal.pone.0173883.
• Stanga PE, et al. PLoS One. 2017;doi:10.1371/journal.pone.0178462.

• For more information:
• Amar Agarwal, MS, FRCS, FRCOphth, can be reached at Dr. Agarwal’s Eye Hospital, 19 Cathedral Road, Chennai-600 086, India; email: dragarwal@vsnl.com.
• Carl C. Awh, MD, can be reached at Tennessee Retina, 345 23rd Ave., Nashville, TN 37203; email: carlawh@gmail.com.
• Kevin J. Blinder, MD, can be reached at The Retina Institute, 1600 S. Brentwood Blvd., Suite 800, St. Louis, MO 63144; email: kjblinder@gmail.com.
• Dhivya Ashok Kumar, MD, FICO, can be reached at Dr. Agarwal’s Eye Hospital, 19 Cathedral Road, Chennai-600 086, India; email: susruta2002@gmail.com.
• Anusha Venkataraman, MD, FRCS(Glasg), FICO, can be reached at Dr. Agarwal’s Eye Hospital, 19 Cathedral Road, Chennai-600 086, India; email: anu_262@rediffmail.com.

Disclosures: Agarwal and Awh report they are consultants for Bausch + Lomb. Blinder reports he is a consultant for Regeneron Pharmaceuticals, Allergan and Bausch + Lomb. Kumar and Venkataraman report no relevant financial disclosures.

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