The PAL Technique for Dropped Nuclei

Dropping a lens fragment into the vitreous cavity during phacoemulsification is one of the most traumatic complications for a cataract surgeon, and can happen to even those most experienced and gifted. Although the situation may appear hopeless, it is important to sit back, catch your breath, and plan an appropriate rescue strategy. To retrieve dislocated nuclear material during surgery, Charles Kelman, MD, introduced the concept of using a pars plana incision to lift dislocated lens fragments anteriorly in order to safely remove them, thus coining the term posterior-assisted levitation, or the PAL technique.1

THE PAL TECHNIQUE
Prior to retrieving the lens, examine the posterior segment with indirect ophthalmoscopy or with a vitrectomy lens to appropriately plan your maneuvers. In most patients, the PAL technique can be safely and effectively performed under topical anesthesia with adjunctive subconjunctival lidocaine. To begin, create a localized conjunctival peritomy at an accessible location (avoiding the superior quadrant and the 3- and 9-o'clock positions) and use cautery for hemostasis. At 3 mm posterior to the limbus, use an MVR blade to make a pars plana sclerotomy (Figure 1). Through the sclerotomy, position a 27-gauge cannula just under the dislocated lens fragment and use an upward motion to lift the fragments into the AC. While in the eye, it is important to visualize your instruments at all times.

AVOID VITREOUS TRACTION
Minimizing traction on the vitreous base is an important consideration in the PAL technique. Make the sclerotomy with a sharp 20-gauge MVR blade and use small bore instruments that can reduce vitreous traction. It is critical to recognize a dropped lens early. Attempt to levitate the nuclear fragment only if it is not entangled in vitreous. If this is the case, first perform a bimanual limbal and/or pars plana partial vitrectomy, and then use a dispersive viscoelastic to support the lens fragments and compartmentalize the vitreous. Perform the vitrectomy at higher cut rates (ie, 400 to 600 cpm) with low flow rates, and infusion through a separate irrigation line via a 23-gauge AC maintainer or butterfly needle to adequately maintain the AC.

LEVITATION
Once it is certain that you have partitioned the dislocated nuclear material from the vitreous, position the cannula directly under the fragments and gently levitate them anteriorly (Figure 2). At this point, use a viscoelastic to push the lens anteriorly and the vitreous posteriorly, as described by Richard Packard, MD.2 It helps to place the tip of the cannula into the lens substance prior to advancing the plunger in order to avoid inadvertently injecting viscoelastic into the vitreous. I have found that air may also be useful in tamponading vitreous when injected under the lens substance.

EXTRACTION
Once you have levitated the lens into the AC, place a phaco glide through a slightly enlarged phaco incision to act as a pseudo-posterior capsule and protect the nuclear fragments from dislocating further. Using a low-flow, low-vacuum phaco technique with reduced infusion, emulsify the nuclear fragments in the AC (Figure 3). Be sure to use a dispersive viscoelastic to provide optimal corneal endothelial protection. It is critical to maintain the AC when removing the phaco handpiece from the eye to prevent vitreous prolapse. Alternatively, you may enlarge the wound and remove the nuclear fragments by manual extraction methods. Manage the cortex by using a dry aspiration technique, or with the I/A Cut mode on the vitreous cutter through a limbal and/or pars plana incision (in this case, lower your cut rate and increase the flow rate accordingly).

Depending on the degree of capsular support, place either a sulcus or a sutured posterior-chamber IOL, or an AC lens. Note that maintaining the integrity of the anterior capsule is paramount to IOL placement, and you should consider it when performing intraocular manipulations and vitrectomy. If available, place a self-sustaining fundus viewing lens on the cornea to view the posterior segment in order to determine whether there is residual nuclear material that you may be able to access with the vitreous cutter. You can adequately visualize the anterior vitreous cavity without a light pipe. Ensuring that the sclerotomy is free of vitreous, close it by placing an 8–0 polyglactin 910 suture (Vicryl; Ethicon, Inc., Somerville, NJ) in an overlapping fashion and closing the conjunctiva with a simple interrupted suture. Postoperatively, regularly perform a complete peripheral retinal examination with scleral depression to recognize and manage potential retinal complications, particularly adjacent to the sclerotomy site.

WHEN TO USE THE PAL TECHNIQUE
Use the PAL technique when lens fragments have dislocated sufficiently to make anterior retrieval alone difficult. Ideally, perform this as early as possible to minimize vitreous prolapse, and use it in cases of posterior capsule tears and zonular dialysis. However, if the nucleus has dislocated too far posteriorly, I do not advise using the PAL technique, as the fragments have likely become entangled in vitreous. Unless you are able to free the nuclear material of vitreous entanglement, do not attempt to levitate them for fear of excessive vitreous traction.

MIYAKE-APPLE STUDIES
To further analyze this technique, we studied human cadaveric eyes using the Miyake-Apple technique with posterior video recording (Figure 4).3 We found that posterior-assisted levitation as previously described caused minimal traction on the vitreous base and was effective in levitating nuclear fragments that had dislocated into the anterior vitreous cavity. We concluded that, when performed correctly, the PAL technique is a safe and effective method of lens retrieval.

ADVANTAGES
Advantages of the PAL technique include avoiding a second surgery, quicker rehabilitation, and reduced postoperative complications including uveitis and glaucoma.4 Indiscriminate “fishing” for dislocated lens fragments deep within the vitreous cavity may result in significant vitreous base traction and risks a giant retinal tear and/or retinal detachment. However, with prompt recognition, early management of vitreous prolapse, and using the PAL technique, this may be safely performed with minimal traction. Finally, it is important to consider that when managing any surgical complication, each surgeon must work within his or her own comfort zone and skill level. n

Iqbal Ike K. Ahmed, MD, is Clinical Assistant Professor at the University of Utah, and is an instructor at the University of Toronto. He may be reached at (905) 456-3937; ike.ahmed@utoronto.ca.
1. Kelman CD. Posterior assisted levitation. In: Burrato L, ed. Phacoemulsification: Principles and Techniques. Thorofare, NJ: Slack Incorporated; 1998:511-512.
2. Packard RBS, Kinnear F. Manual of cataract and intraocular lens surgery. Churchill Livingstone, 1991 [videotape]. European Society of Cataract and Refractive Surgeons Annual Meeting, 2000.
3. Ahmed IK, Crandall AS. Video Analysis of the Posterior Assisted Levitation Technique [videotape]. ASCRS Symposium on Cataract, IOL and Refractive Surgery Film Festival. Philadelphia, PA; 2002.
4. Kageyama T, Masahiko A, Ogasawara M, et al. Results of vitrectomy performed at the time of phacoemulsification complicated by intravitreal lens fragments. Br J Ophthalmol. 2001;85:1038-1040.