Tools and techniques
Pars plana vitrectomy for the anterior segment surgeon

Dealing with capsule ruptures and vitreous presentation is one aspect of anterior segment surgery that the average cataract surgeon dreads. I believe this is in part due to a lack of adequate training and experience with this infrequent complication of cataract surgery. In this month's column, Lisa Arbisser, M.D., presents an incredibly valuable systematic approach for successfully conquering vitreous. This article gives useful tips and pearls in addition to a better understanding of proper machine settings for 20-gauge and smaller vitrectors. This is an extremely useful article that I believe should be read repeatedly, especially before your next difficult and challenging case. I am confident you will find this educational and practical.

Richard Hoffman, M.D., Tools & techniques editor

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Dr. Arbisser, adjunct clinical associate professor, John A. Moran Eye Center, University of Utah, Salt Lake City, discusses the settings and strategies involved for optimal outcomes

In complicated cataract cases involving vitreous, our primary goal is to avoid intra-op and post-op retinal traction. Sequelae of tears and detachment are the primary reasons for poor outcomes. Our secondary goal is to leave a clean anterior segment and a stable intraocular lens while avoiding collateral capsule, iris, and corneal damage.
Early capsule breach recognition helps limit complications progressing from ruptured posterior capsule with intact hyaloid to vitreous prolapse to extraocular vitreous loss. Retained lens material may further complicate matters. Satisfactory resolution and prognosis requires an individualized approach that, if appropriately handled, can maintain excellent chances for an optimal outcome even if a second surgery should occur for retained lens material.

Complication control

Vitreous follows a gradient from high to lower pressure. When suspicious of a complication, surgeons should seek a static environment by filling the anterior chamber with dispersive viscoelastic (OVD) through the side port to avoid anterior chamber collapse when removing instruments from the main incision. Surgeons can then safely inspect and plan. Whenever possible, convert rents of any shape to a continuous rhexis (PCCC). Push the hyaloid face posteriorly and protect with OVD for subsequent maneuvers. Seal the posterior segment by implanting a three-piece IOL with haptics in the bag and optic captured through an adequately sized PCCC. Ignore OVD behind the IOL. OVD anterior to the lens can be efficiently removed without representation of vitreous.
If the hyaloid is breached, our goals include limiting vitreous travel, removing the least amount necessary so none is left above the level of the posterior capsule, and limiting collateral damage. Identifying nearly invisible vitreous with Triesence (triamcinolone acetonide injectable suspension, Alcon, Fort Worth, Texas) is helpful in defining the endpoint of removal and warning of representation.
Except for a small wisp sharply cut with intraocular scissors and teased back into the posterior segment with OVD, automated vitrectomy is appropriate. The cellulose sponge technique many of us learned creates traction both by capillary action and by lifting. Sweeping the incision to disengage vitreous from the wound, another historical maneuver, also creates huge tractional force through the pupil, which transfers to thin peripheral retina.

Performing the vitrectomy

Older machines may feature a coaxial sleeve over the vitrector; however, current technique mandates the biaxial approach. Anterior segment surgeons should irrigate through a clear corneal side-port incision or chamber maintainer and not coaxially with the vitrector or through a pars plana incision.
Introduce the vitrector through a snug separate clear corneal paracentesis or an MVR or trochar pars plana incision 3.5 mm posterior to the limbus. The pars plana approach is more efficient, less likely to engage the capsule or iris, and better amputates a sheet of vitreous to the wound from its posterior connection. The pars plana approach encourages vitreous back, removing less, and, because it creates lower pressure in the posterior segment, better discourages representation of vitreous during subsequent maneuvers. I prefer a clear corneal incision mainly when the pupil view is obscured. Trochars permit two-plane circumferential sutureless sclerotomies but require more pressure to insert than sharp MVR entry; they are best employed only when incisions are watertight and eyes are normotensive. Always avoid the main clear corneal-sleeved phaco incision, which allows vitreous to escape around the bare vitrector. Anterior segment surgeons should strive to learn to safely make and close pars plana sclerotomies because of the many advantages.
During vitrectomy the foot pedal is always set so foot position (FP) 1 initiates irrigation, FP 2 cutting, and FP 3 vacuum. Though this FP order can be reversed when followability is desired, as with cortex removal, the vitrector must always be cutting when sucking vitreous or traction damage results. Unless FP 3 is engaged, cutting occurs without vitreous removal.
Vitrectomy settings should limit port-based flow, and therefore vitreous traction, by setting the highest cut rate available. This ranges from 400 on older machines to 2,500 cuts/min on newer models. Take your time with a low aspiration flow rate—usually 20 is panel set for 20-gauge vitrectomy and 15 for 23-gauge. Vacuum must be at the lowest setting that results in removal of vitreous; generally 200-250 for 20-gauge and 350-500 for 23-gauge. This varies depending on how much dispersive OVD is present and will usually need to be higher than the default setting, which is best for our retina-vitreous colleagues who do not have OVD present at all during the pars plana approach. Many machines default to linear for vacuum in vitrectomy mode, but I prefer that the scrub assistant adjust the vacuum up until effective on panel setting. This strategy allows the surgeon to be anywhere in FP 3 without regard to excursion. Many surgeons are tentative during a complication. Pedal to the metal is less challenging, more efficient, and in the long run safer. The irrigation bottle height seeks a normotensive eye, around 80 cm, while the vacuum is active. This can be similarly adjusted by the scrub at the surgeon's direction. These parameters are not absolute; however, the goal is cutting the vitreous matrix as frequently as possible with low flow limiting traction, while balancing vacuum and irrigation, keeping a formed chamber and a normotensive eye.
The activated vitrectomy port should always be visible through the pupil and should never be moved through vitreous with FP 3 (vacuum) activated. On completion of the vitrectomy, FP 2 is maintained while moving the vitrector until the port is no longer visible. FP 1 is maintained until just before the vitrector leaves the eye in FP 0. Ultrasound cannot cut vitreous. It cannot be refluxed from an irrigation and aspiration port once incarcerated. At the endpoint of prolapsed vitreous removal, all subsequent maneuvers to remove lens material and place a stable IOL should only take place when the posterior segment and vitreous is compartmentalized by OVD partitioning or a captured optic sequesters it from the anterior structures. Finally, the risk of endophthalmitis is higher with a broken hyaloid. Surgeons should consider systemic prophylaxis and treat pressure spikes prophylactically. Monitoring and controlling inflammation to avoid CME is also important. Early post-op referral for retained lens fragments and peripheral retina indented exam is mandatory. Surgeons should disclose complications to patients despite what may be an optimal post-op result.

Editors' note: Dr. Arbisser has financial interests with Abbott Medical Optics (Santa Ana, Calif.) and Alcon.

Contact information

Arbisser: 563-323-2020, drlisa@arbisser.com