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Small-gauge, high-cut advancements available for anterior vitrectomy
Upgrades in phaco platforms help cataract and anterior segment surgeons who perform vitrectomy.
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Vitreous management, with the required tools and surgical skill set, should be an integral part of every cataract and anterior segment surgeon’s armamentarium in order to provide optimal visual outcome for patients after complicated cataract surgery or other anterior segment surgery, including penetrating keratoplasty and sutured or scleral pocket-fixated posterior chamber IOL implantation.
Vitreous in its undisturbed, resting state for the most part causes little visual compromise. However, when the anterior hyaloid membrane of the vitreous is violated and barriers such as the posterior capsule are accidentally torn during cataract surgery, or when ocular trauma is sustained preoperatively, the vitreous then follows via the path of least resistance and moves forward, often into the anterior chamber. This forward vitreous displacement results in the “slinky” concept, as described by Dr. Paul Koch, of being stretched anteriorly, and this can result in secondary traction in the posterior segment, namely on the retina. Such retinal traction can lead to macular edema, possible retinal detachment and compromised vision.
Cataract surgeons have traditionally performed vitrectomy through an anterior approach, but the time has come to consider a change in direction and transition to transconjunctival pars plana triamcinolone-assisted vitrectomy with a bimanual technique, in which the “slinky” will be less stretched compared with conventional anterior vitrectomy, which may contribute to an overall less amount of vitreous being removed and possibly an overall better surgical outcome. The standard approach for anterior vitrectomy is using a lower vacuum setting combined with an increased cutting rate that allows for a relatively safe vitrectomy procedure. Technological advances in phaco platforms can now offer an increased cutting rate from 600 cuts/minute to 2,500 cuts/minute, and the choice of using a 23- or 25-gauge cutter will further decrease the wound size.
In this column, Dr. Raviv describes new advances in anterior vitrectomy that can be used by cataract and anterior segment surgeons.
Thomas John, MD
OSN Surgical Maneuvers Editor
While pars plana vitrectomy by retina specialists has advanced by leaps and bounds with smaller gauge instrumentation and higher cut rates, anterior vitrectomy technology has lagged behind. Most cataract surgeons are limited to the vitrectomy parameters of their phaco machines, which until recently have been 20 gauge and low cut.
Fortunately, recent upgrades in phaco platforms such as the WhiteStar Signature (Abbott Medical Optics) allow anterior segment surgeons to utilize the latest advancements in vitrectomy. Surgeons can now perform 23- or 25-gauge high-cut anterior vitrectomy without having to bring in additional specialized instrumentation. With the WhiteStar Signature, the 23-gauge vitrector comes standard (and for me has completely replaced the traditional 20-gauge cutter), while a third-party 25-gauge cutter can also be directly connected.
Advanced anterior vitrectomy
Older phaco machines limited their anterior vitrectomy to 600 cuts/minute, but the WhiteStar Signature offers cut rates up to 2,500 cuts/minute. Higher cut rates induce less traction and increase procedure safety. Furthermore, anterior segment vitrectomy has progressed from a coaxial procedure to a biaxial one, with irrigation separated from the cutter. This setup is preferred because it avoids hydrating or pushing the vitreous away from the cutting area. Using a 20-gauge cutter requires significant enlargement of the paracentesis and causes leaky wounds, but the 23-gauge cutter can fit through a 1-mm paracentesis, and the 25-gauge cutter through an even smaller paracentesis. This more watertight closure allows for better chamber maintenance with added maneuverability.
Planned or unplanned vitrectomy
While the frequency of vitreous loss during cataract surgery and unplanned vitrectomy has decreased, it is still a relatively common occurrence in the 3 million annual cataract surgeries performed in the U.S. By having a vitrectomy standard of 23 gauge and 2,500 cuts/minute, surgeons can perform a clean, efficient and safer anterior vitrectomy through any paracentesis. This prevents the frequent vitreous wicking to the wound that was commonly seen with less watertight 20-gauge systems.
I also use 23- or 25-gauge vitrectomy in a planned manner under three different scenarios. First would be in cases of cataract with significant pre-existing zonular dehiscence and vitreous prolapse, such as after trauma. Second would be when performing complex IOL procedures, such as IOL exchange after Nd:YAG or IOL repositioning/suture fixation. And third would be when performing a limited pars plana deepening before cataract extraction in an eye with an extremely shallow anterior chamber.
Anterior or pars plana vitrectomy
The 23- or 25-gauge vitrectors can also be used via a pars plana route. Because anterior segment surgeons have to remove only a small amount of anterior vitreous, the setup is much simpler than the typical three-port pars plana vitrectomy and is well within the reach of most anterior segment surgeons. I use a one-port transconjunctival pars plana entry with a separate anterior chamber maintainer through a paracentesis. In cases requiring chamber deepening before phaco, I proceed with vitrectomy until the anterior chamber safely deepens. When used to remove anteriorly prolapsed vitreous, a one-port pars plana vitrectomy allows exquisite control and better visibility.
The pars plana route allows for less vitrectomy to be performed. Because vitreous is not continually pulled forward but rather drawn back, a more limited vitrectomy is needed. Another benefit of using this technique is that once the port is made, the surgeon can plug it and regain access to the vitrectomy area when necessary, just as a retina surgeon would do. This is especially helpful if more vitreous needs to be removed after the lens is placed. The surgeon can easily clean it out by going through the port and not disturbing the wound again.
Preparing to insert capsular hook.
Images: Raviv T
Gentle phacoemulsification.
Ab externo approach through a sclera groove.
Capture and pass double-armed 10-0 Prolene through a long 26-gauge needle.
The versatility of using the 23- and 25-gauge vitrectomy cutters with 2,500 cuts/minute throughout my standard phaco platform makes for safer and more efficient surgeries.
Complex case
In a recent case involving a patient with a complex traumatic cataract with severe zonular dialysis and vitreous prolapse, I began by performing a one-port 25-gauge pars plana vitrectomy transconjunctivally to clear the anterior vitreous (visualized with triamcinolone). For this technique, I utilized an irrigating cannula to pressurize the anterior chamber and prevent further vitreous prolapse.
After initiating the capsulorrhexis, I carefully centered it upon the lens itself. An iris or capsular hook was used initially to stabilize the lens and then an Ahmed capsular tension segment was hooked for additional support. Hydrodissection prolapsed the lens away from the capsule to further minimize zonular trauma. Using Venturi fluidics set at a maximum vacuum of 75 mm Hg, gentle phacoemulsification was then done. Slowly and carefully the lens was removed without trauma to the zonules. The capsule was further supported with a standard capsular tension ring, which distributed the forces of the healthy zonules over the area of the missing zonules. This allowed the entire capsule to be suture fixated using one capsular tension segment. Next, using an ab externo approach via a scleral groove, I passed and captured a double-armed 10-0 Prolene long needle through the eyelet of the capsular tension segment and fixated it to the sclera, achieving good centration. The 25-gauge vitrectomy port remained available to provide for any additional vitreous removal should it have become necessary. Finally, the IOL was placed, and excellent centration in the bag was achieved.
More options
With the vitrectomy mode on the WhiteStar Signature, the surgeon can choose the Venturi or the peristaltic setting, just as with the phaco portion of the surgery. I use Venturi fluidics for vitrectomy because this has been the standard in retina surgery and might offer some advantages over peristaltic. The versatility of a dual pump with the WhiteStar Signature gives the surgeon more options.
Overall, cataract surgeons can now perform anterior vitrectomy, to the advantage of our cataract patients, using proven advancements currently employed by retina specialists.