Hypersonic vitrectomy can be used during complex cases
The hypersonic vitrector is a novel ultrasound-based vitreous removal device that uses ultrasound power ranging from 27 kHz to 31 kHz, near the range of conventional phacoemulsification of 40 kHz; however, the stroke length varies between 0 µm and 60 µm.
The Vitesse hypersonic vitrectomy system (Bausch + Lomb) consists of a 23-gauge vitrectomy probe and a 33-mm long stainless steel needle with a 255-µm sized teardrop port at the tip, which oscillates with user-controlled amplitude. The Vitesse vitrectomy handpiece uses ultrasonic, harmonic needle tip movement at 28.5 kHz to generate fluidic and mechanical cutting action for fragmenting and removing vitreous.
Device and mechanisms
The Vitesse vitrectomy system includes the Vitesse vitrectomy handpiece; the Bausch + Lomb Stellaris Elite vision enhancement system with hardware and software modifications to include Vitesse vitrector drive circuitry, a handpiece connector port and graphical user interface controls for operating the handpiece; and the Vitesse transconjunctival entry site alignment cannula system for introducing the Vitesse needle, existing fluid infusion cannula and existing light probes into the posterior segment of the eye. The Vitesse vitrectomy needle is 23 gauge and 33 mm long and has an outer diameter of approximately 0.64 mm. It is made of 304 stainless steel and coated with titanium nitride for wear-resistance and lubricity. The needle has a closed distal end and a side port with a diameter ranging from 175 µm to 255 µm and a port with various configurations. The needle reciprocates with constant frequency, user-controlled amplitude (stroke length) of 0 µm to 60 µm, peak to peak. The device draws vitreous to the needle port, and then liquefies and aspirates the vitreous out of the eye into a disposable fluid collection cassette through the attached tubing.
Anterior vitrectomy using hypersonic vitrector
We have used hypersonic vitrectomy in an eye with a ruptured posterior capsule with vitreous in the anterior chamber in a complicated cataract surgery. The minimal cortical and epinuclear lens particles in the anterior chamber were also liquefied and aspirated via the Vitesse vitrectomy system. The postoperative period was uneventful with clear cornea, normal fundus and 20/20 best corrected visual acuity stable at 3 months’ follow-up.
Triumvirate technique with hypersonic vitrectomy
A trocar anterior chamber maintainer was inserted at the inferotemporal quadrant 7 clock hours at the limbus. Two scleral flaps about 180° apart were fashioned at 3 and 9 o’clock hours. The Vitesse probe was introduced through the side port, and the vitreous in the anterior chamber was removed (Figure). The stroke length ranged from 30 µm to 40 µm, and the vacuum was 160 mm Hg to 250 mm Hg. The retained cortex in the anterior chamber was also liquefied and aspirated simultaneously into the probe. A three-piece foldable IOL was injected through the main port to act as scaffold for nuclear fragments. Further lens fragments were liquefied and removed over the IOL. Two sclerotomies were subsequently performed below the scleral flaps and for the subsequent glued IOL procedure. Iris retractors were used to expose the peripheral cortex removal and visualization. Vitrectomy was continued at the pupillary plane below the iris and on the IOL. Lens fragments dropped in the vitreous were removed by posterior vitrectomy with the same probe inserted through the sclerostomy site and the illumination probe through the other sclerotomy. Once the vitreous was cleared from the pupillary plane and anterior chamber, the glued IOL procedure was performed by intrascleral tucking of the haptic on either end. The trocar anterior chamber maintainer was removed, and the anterior chamber was formed by an air bubble. Then the scleral flaps were opposed by fibrin glue.
Hypersonic vitrectomy and conventional vitrectomy
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-gauge, 23-gauge and 25-gauge cutters achieve high vitreous flow rates. Even though new-generation cutters maintain high flow rates with increasing speed, there are some limitations related to the mechanical cutters, including the turbulences created by the periodic opening and closing of the port. Although increasing the cut rate reduces this turbulence somewhat, any cutter with a periodically closed port will result in this effect, and the advantage of increasing the cut rate appears to be dwindling.
The usual limitations with guillotine include the turbulence created by the periodic opening and closing of the port, vitreous material may be caught between the inner needle and the port edges, and the outer needle port must be large enough to permit a reasonable amount of tissue to enter to achieve a cut. Rather than being cut, the vitreous is aspirated uncut, or partially cut, through the port, resulting in direct traction on the vitreous strands. The initial studies by Stanga and colleagues have shown the efficacy of the hypersonic vitrector to overcome the above limitations of the guillotine vitrector in vitreous.
Stanga and colleagues have reported the initial results on the efficacy of hypersonic vitrectomy ex vivo in which they compared the conventional guillotine vitrector with the hypersonic vitrector in vitro between the vitreous and the water. The hypersonic vitrectomy system uses low amplitude motion of the tip to create oscillating high-speed flows near the port that “cut” vitreous. It also liquefies the vitreous in the vicinity of the port tip to the viscosity of water. This allows the hypersonic vitrector to address some of the limitations of the guillotine vitrector. 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 the use of smaller port and larger inner-lumen diameters, which in turn lowers flow resistance with less dependence on infusion pressures. An additional ex vivo study on porcine eyes showed histological features of the tissue similar in guillotine and hypersonic vitrector postoperatively. As we know with the improvised microvitrectomy instrumentation (23 gauge or 25 gauge), the reduction in incision size alone may not help because the drawback of low flow rate and sometimes greater vitreous traction with smaller-gauge vitreous cutters can persist.
Lens and vitreous liquefaction
Posterior assisted levitation is a known procedure for a dropped lens in the anterior vitreous, and in this case we have combined with the IOL scaffold method and glued IOL. The epinuclear lens fragments in the anterior vitreous have been emulsified by the same hypersonic vitrector probe along with the vitreous. Although the case is the first of its kind in which a hypersonic vitrector is utilized for anterior vitreous and lens removal in a posterior capsular rupture, the effectiveness of the vitrector with a hard nucleus is unidentified. Nevertheless, the hypersonic vitrector has shown effective removal of the vitreous from the anterior chamber and pupillary plane with simultaneous retained lens particle removal.
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- For more information:
- Amar Agarwal, MS, FRCS, FRCOphth, is director of Dr. Agarwal’s Eye Hospital and Eye Research Centre. Agarwal is the author of several books published by SLACK Incorporated, publisher of Ocular Surgery News, including Phaco Nightmares: Conquering Cataract Catastrophes, Bimanual Phaco: Mastering the Phakonit/MICS Technique, Dry Eye: A Practical Guide to Ocular Surface Disorders and Stem Cell Surgery and Presbyopia: A Surgical Textbook. He can be reached at 19 Cathedral Road, Chennai 600 086, India; email: firstname.lastname@example.org; website: www.dragarwal.com.
Disclosures: Agarwal reports he is the principal investigator of the trial. Kumar reports no relevant financial disclosures.