Mastering Bimanual Microincision Phacoemulsification
Use the techniques that lead to superior outcomes.
BY MARK PACKER, M.D., F.A.C.S., I. HOWARD FINE, M.D., RICHARD S. HOFFMAN, M.D.

The advantages of microincision phaco outweigh any increased difficulty or complications that occur during a surgeon's early experience with the technique. These advantages include:

• enhanced chamber stability thanks to a more nearly perfectly closed system
• better followability due to separation of infusion and aspiration
• access to 360 degrees of the anterior segment with either infusion or aspiration by switching instruments from one hand to the other
• the ability to use the flow of irrigation fluid as a tool to move material within the capsular bag or anterior chamber (particularly from an open-ended irrigating chopper or manipulator)
• significantly decreased chance of vitreous prolapse in the case of a posterior capsular tear or rupture thanks to maintenance of a pressurized stream of irrigation from above.

ILLUSTRATION: JOEL & SHARON HARRIS/DEBORAH WOLFE, LTD

To reap the benefit of these advantages, strict attention to detail is required. In this article, we'll describe the techniques we use to achieve superior outcomes.

The Incision

The first technique to master is construction of the incision. Variability in incision size will occur among surgeons who employ 20-gauge, 19-gauge and even 18-gauge instrumentation. We prefer 20-gauge because we feel it offers greater control.

Because the outer diameter of the 20-gauge tip is 0.9 mm, the circumference of the tip is 2.8 mm and the incision must measure 1.4 mm. An incision smaller than 1.4 mm stretches and tears, causing loss of self-sealability. These microincisions are converted from a line to a circle upon introduction of the tip, and we want them to resume the configuration of a line when the tip is withdrawn. Compromise of the corneal collagen by stretching or tearing will reduce the likelihood that the incision will resume its virgin architecture at the end of the case. There are now available from a variety of manufacturers diamond and metal knives specially designed for construction of 20- or 19-gauge incisions. It behooves the surgeon to purchase and learn to use this instrumentation, whether constructed of steel, diamond or other material.

Constructing the Capsulorhexis

Capsulorhexis construction represents the greatest hurdle in the bimanual learning curve. We initially began this technique with a bent-needle cystotome, and this continues to represent a valid technique. However, microincision capsulorhexis forceps permit a greater degree of precision and control, so much so that we advocate their use with any type of incision. The pinch-type initiation of the capsulorhexis is particularly valuable in cases of zonular compromise because the forces acting on the capsule remain balanced.

Even with a severely wrinkling capsule due to traumatic zonular dialysis, these extraordinarily delicate forceps permit moment-by-moment control of the capsulorhexis. With new technology IOLs, such as the crystalens (eyeonics, Aliso Viejo, Calif.), we have found capsulorhexis size to be an important determinant of final lens position and therefore postoperative refractive status. Using microincisions enhances the precision of capsulorhexis construction, not only because of the improvements in instrumentation, but also because we can eliminate the tendency for the chamber to shallow, as often occurs with a 2.5-mm incision due to burping of viscoelastic.

Capsulorhexis Control

Increased risk of losing control of the capsulorhexis exists in highly myopic eyes with very large, floppy capsules. Due to the extremely long anterior chamber depth in these eyes, the angle of approach to the anterior capsule is much steeper. If one notices that the capsulorhexis is tearing out further peripherally than one would like, a simple technique for capsulorhexis recovery involves laying down the flap and pulling centripetally. This maneuver redirects the capsulorhexis centrally. However, this technique will not suffice if the capsulorhexis has already run out as far as the zonular attachments. In this case, it is likely necessary to cut the flap with scissors and begin the tear anew. Microincision intraocular scissors suitable for this purpose are now available.

Capsulorhexis control represents a critical step in the phacoemulsification of the opaque, mature lens. Capsule staining with trypan blue dramatically enhances the visibility of the capsule, permitting accurate construction of a continuous curvilinear tear. Maintenance of a stable chamber is enhanced by the microincisional technique because the viscoelastic device cannot egress from the wound during completion of the capsulorhexis, as often happens with a larger incision and bulkier forceps. With a stable chamber and a distinct capsular flap, an otherwise difficult procedure is converted into a routine step in surgery.

Hydrodissection and Hydrodelineation

The goal of cortical cleaving hydrodissection as described by Howard Fine, M.D., lysis of the equatorial capsular-cortical connections, will generally ensure aspiration of the cortex along with the epinucleus, obviating the need for a separate irrigation/aspiration (I/A) step. Hydrodelineation is performed to allow free mobility of the endonucleus within the epinuclear shell, allowing endocapsular nuclear disassembly within the safety cushion of the epinucleus.

Hydrodissection and hydrodelineation may be performed just as they are with standard small-incision surgery; the microincisions do allow egress of viscoelastic during this step so that there is not an increased risk of blowing out the posterior capsule due to over-pressurization. Of note, we found that the intraocular pressure during hydrodissection, as measured in the vitreous cavity of a cadaver eye, varies around means of 78 to 223 mmHg regardless of whether a standard small incision or microincision is employed. (Khng C, Packer M. "Intraocular Pressure During Phacoemulsification" [poster]. XXII Congress of the European Society of Cataract and Refractive Surgery. Paris, 18-22 September 2004.)

These were among the highest pressures we recorded during the entire phacoemulsification and IOL implantation procedure. Clearly, if viscoelastic is prevented from exiting the eye, there is adequate pressure to rupture the capsule. This represents a special concern to users of high zero-shear viscosity ophthalmic viscosurgical devices (OVDs), who should insure that a path for egress is prepared with a track of balanced salt solution from the cannula tip to the incision.

Using Bulkier Choppers

A variety of irrigating choppers are now available for microincision surgery. How to place the blade or paddle of the chopper through the incision is not always immediately apparent. With the canoe paddle-shaped Tsuneoka Chopper (MicroSurgical Technologies, Redmond, Wash.), for example, the paddle must be placed parallel to the incision, inserted into the chamber and then rotated to allow full entry. Surgical videos are generally available from industry for instructional purposes. Placing the phaco tip through the incision may also be harder than it first appears. A 30-degree tip may be inserted into the incision bevel down, and then rocked gently from side to side to permit passage into the chamber.

The surprising fact about horizontal and vertical chopping techniques with bimanual phaco is how little they differ in terms of hand movement from standard small- incision coaxial phaco. Seeing the bulkier irrigating chopper in the eye and getting used to the heavier feel in one's hand represent the major differences; the actual chopping techniques are the same. The stream of irrigation fluid from the chopper or manipulator can function as an efficient tool within the eye and is one of the most significant advantages of bimanual phaco, a key reason we don't want to go back to coaxial.

The Bimanual Advantage

In particular, washing subincisional endo- or epinuclear material into the range of the phaco tip permits enhanced safety and control. A great example is Refractive Lens Exchange with an accommodative IOL in high myopia, probably the situation in which we are most concerned about maintaining the integrity of the capsule. Not only would compromising the capsule increase the risk of posterior segment complications, but it would also mean not implanting the IOL of choice for the procedure. With bimanual phaco, no instrument other than a cannula and a stream of fluid ever need enter the space within the bag. We can manipulate the soft lens material into the anterior chamber with the stream of irrigation fluid and aspirate it safely from the eye with vacuum alone. Thanks to cortical cleaving hydrodissection, we can achieve a clean capsule without ever placing an aspiration tip below the level of the capsulorhexis. The margin of safety is enhanced by this approach.

If there is a breach of the posterior capsule, residual lens material can generally be removed while maintaining irrigation in the anterior chamber and disallowing vitreous prolapse. With bimanual phaco, we have the option of switching from a phaco tip, to an aspirator, to a vitrectomy cutter if necessary without ever losing chamber stability. The approach, once a tear is recognized, consists of continuous irrigation in the anterior chamber while lens material is removed from the bag. Once the bag is clean, a dispersive viscoelastic is injected at the level of the posterior capsule while irrigation is still maintained; only once the viscoelastic has fully tamponaded the break and filled the chamber is the irrigator removed. The IOL can then be inserted into the ciliary sulcus or the capsule through a standard temporal clear-corneal incision. In the case of sulcus placement, the optic is pushed posteriorly through the capsulorhexis prior to final clean-up. Once viscoelastic is removed, the kenalog technique described by Scott Burke, M.D., is utilized to ensure a completely vitreous-free environment in the anterior segment.

The Future of Phaco

The many advantages of bimanual microincision phaco are easily accessible to the skilled cataract surgeon. Microincision IOLs, already available outside the United States, will soon create a rush to these enhanced techniques. But regardless of the final incision size required for IOL insertion, microincision phaco stands on its own as a superior technique.

At the Casey Eye Institute at Oregon Health & Science University in Portland, Dr. Fine is a clinical professor, Dr. Packer is a clinical assistant professor, and Dr. Hoffman is a clinical associate professor. Their practice, Drs. Fine, Hoffman & Packer, LLC, is located in Eugene, Ore.