6.8Biaxial Microincision Phacoemulsification: Transition, Techniques, and Advantages

Richard S. Hoffman, I. Howard Fine, and

Mark Packer

Core Messages

ßThe learning curve for the transition from coaxial phacoemulsification to biaxial micro-

incision phacoemulsification is a relatively short and a safe one.

ßThe real benefits of biaxial microincision phacoemulsification stem from the ability to

approach the lens from two different directions, rather than the benefits inherent in microincisions.

ßDifficult and challenging cases such as pseudoexfoliation, subluxed, traumatic, mature,

and posterior polar cataracts, are best addressed with a biaxial technique.

ßThe ability to maintain the infusion above the plane of the iris during phacoemulsification

and the aspiration of the cortical material has allowed for better stabilization of the anterior chamber and less induced miosis in IFIS (intraoperative floppy iris syndrome) cases.

The idea of removing the cataractous lens through two microincisions is not a new concept and has been attempted with varying degrees of success and failure since the 1970s [1–3, 7–9]. With the development of new phacoemulsification technology and power modulations [5], we are now able to emulsify and fragment the lens material without the generation of significant levels of thermal energy. Thus, the removal of the cooling irrigation sleeve and the separation of infusion and emulsification/aspiration through two separate incisions is now a viable alternative to traditional coaxial phacoemulsification.

Although the incision size is considered as the main advantage for a microincision technique, the greatest advantage of biaxial phacoemulsification stems not from the incision size, but from the biaxial approach to lens removal. Although microincisions offer the advantages of less induced astigmatism and perhaps, greater safety following traumatic injuries to the globe, the ability to approach difficult and challenging cases from two different incision locations, in addition to the peculiar fluidics of biaxial irrigation and aspiration, are the strongest assets for this surgical technique.

Although learning any new surgical technique has its intimidating moments, the transition to biaxial microincision phacoemulsification is a relatively straightforward process with a short and a safe learning curve, and requires only a small investment in new surgical instrumentation.

6.8.1 Surgical Technique

The preoperative work-up and the preparation for surgery with regard to antibiotic prophylaxis and dilation drops are essentially the same for biaxial surgery and coaxial phacoemulsification. In this technique, a single 1.2mm incision is created, 30–45° to the left of the temporal limbus using a 1.2mm diamond or steel keratome (Fig. 6.63). A trapezoidal diamond keratome will create an incision configuration with an internal opening of

R. S. Hoffman

Oregon Health & Science University, Drs. Fine, Hoffman and Packer, 1550 Oak Street, Suite 5, Eugene, Oregon 97401, USA e-mail: rshoffman@finemd.com

Fig. 6.63 1.2 mm microincision created to the left using a diamond keratome (Figure courtesy of Richard S. Hoffman)

1.0mm and an external opening of 1.2mm. This is followed by the instillation of 0.5cc nonpreserved Lidocaine 1% and Viscoat. A second microincision is then created 90–120° from the left-sided incision (Fig. 6.64). Placing an OVD into the anterior chamber prior to creating the second microincision will repressurize the eye and insure a more accurate incision length.

The capsulorhexis can be started with a special forceps which is designed to function through a 1.2 mm incision. Most instrument companies are currently manufacturing microincision capsulorhexis forceps although there is a preference for the MST Fine/ Hoffman microincision forceps (# DFH-0002, MicroSurgical Technology, Redmond, WA) (Fig. 6.65). The capsulorhexis is begun by puncturing the central lens capsule with the tips of the microincision capsulorhexis forceps. This is easily accomplished using a single blade of the forceps tip in the open configuration and then grasping the edge of the open capsule with the forceps in the closed configuration (Fig. 6.66). Following the completion of capsulorhexis, cortical cleaving hydrodissection and hydrodelineation are performed with a 26-gauge cannula. Rotation of the crystalline lens following hydrodissection, but prior to hydrodelineation will insure that both the endonucleus and the epinucleus are freely mobile. Once the lens is rotated, hydrodelineation can be performed to separate the epinucleus from the endonucleus and phacoemulsification can be commenced.

Fig. 6.66 OpenconfigurationofMST(MicroSurgicalTechnology) Fine/Hoffman capsulorhexis forceps about to regrasp the anterior rhexis edge to continue and complete the capsulorhexis (Figure courtesy of Richard S. Hoffman)

Chopping is the preferred lens removal technique since it will allow for the lowest amounts of energy to be utilized and will lower any risk of incision burns. A 20-gauge irrigating chopper is inserted through the lefthanded incision followed by the placement of the bare phacoemulsification needle (without an irrigation sleeve) through the right-handed incision. Microsurgical Technology’s MST Duet System, which is available in both vertical and horizontal choppers, is currently preferred (Fig. 6.67). Insertion of the irrigating chopper is a maneuver that requires a short learning curve. It is best accomplished by inserting the vertical chopping element at the tip, parallel to the incision, until the distal aspect of the chopping segment clears the internal opening of the clear corneal incision (Fig. 6.68). Once the internal opening has been cleared, the handpiece can then be rotated to allow the remaining of the chopper to enter the eye.

Fig. 6.68 The vertical element located on the tip of the irrigating chopper is inserted parallel to the incision until the leading edge clears the internal opening of the clear corneal incision (Figure courtesy of Richard S. Hoffman)

After trimming the anterior epinucleus with aspiration from the bare phaco needle, a horizontal chopper is placed at the distal golden ring and the phaco needle is buried proximally into the endonuclues to a depth of 50–60%. Horizontal chopping is then performed by bringing both instruments together and then pulling 90° away to create the first chop. The lens is then rotated 90° with either the chopper or the bare phaco needle and the second chop and segment removal is performed. Removal of the endonucleus is followed by trimming and flipping of the epinucleus, as previously described [4]. Rotating the vertical chopping element (located at the tip of the irrigating chopper), into a horizontal position during the removal of the last endonuclear segment and the removal of the epinucleus will decrease the chances of accidentally tearing the posterior capsule, if the capsule moves anteriorly, at this point in the procedure. If residual cortical material remains, it can be easily removed with the bimanual irrigation and aspiration handpieces (Fig. 6.69a, b).

Fig. 6.69 (a) Magnified view of Duet™ aspiration tip and (b) irrigation tip utilized for bimanual I/A (Figure courtesy of MST MicroSurgical Technology)

6.8.2 Advantages

Why remove a lens through two 1.0–1.2mm incisions rather than a 2.2–2.5mm incision? While it is true that coaxial phaco is an excellent procedure with low amounts of induced astigmatism [6], biaxial phaco offers the potential for truly astigmatic neutral incisions. In addition, these microincisions should behave like a paracentesis incision with less likelihood for leakage and theoretically, a lower incidence of endophthalmitis.

The major advantage observed in biaxial microincisions is the improvement in the control of most of the steps involved in endocapsular surgery. Since OVDs do not leave the eye easily through these small incisions, the anterior chamber is more stable during capsulorhexis construction and there is much less likelihood for an errant rhexis to develop. A more controlled capsulorhexis has been extremely advantageous in cases of pseudoexfoliation, traumatic injury, lens subluxation, and mature cataracts. Also, hydrodelineation and hydrodissection can be performed more efficiently by virtue of a higher level of pressure building in the anterior chamber, prior to the eventual prolapse of the OVD

through the microincisions.

In addition, separation of irrigation from aspiration allows for improved followability by avoiding competing currents at the tip of the phaco needle. In some instances, the irrigation flow from the irrigating handpiece can be used as an adjunctive surgical device – flushing nuclear pieces from the angle or loosening epinuclear or cortical material from the capsular bag. In the same respect, it is important to avoid directing the fluid flow from the irrigating handpiece to the tip of the phaco needle since this will dislodge nuclear fragments from the tip and actually worsen the followability.

The fluidics of separate infusion and aspiration have been extremely advantageous in intraoperative floppy iris syndrome (IFIS). Much of the billowing of floppy irides and the resultant miosis appears to stem from the infusion of the fluid behind the iris plane. With a coaxial technique, the infusion fluid is placed behind the iris plane during lens grooving and virtually all aspects of in situ phacoemulsification unless the lens nucleus is brought up to the anterior chamber for phacoemulsification. Similarly, aspiration of the cortex with a coaxial handpiece creates the same infusion currents behind the iris plane. With a biaxial technique, the infusion can be placed high in the anterior chamber, in front of the iris plane during phacoemulsification, and the aspiration of the cortex has been found to create a much stabler anterior chamber in IFIS cases with less likelihood for iris billowing and subsequent miosis.

Perhaps, the greatest advantage of the biaxial technique lies in its ability to switch handpieces between the similarly sized microincisions located 90° away from each other. The ability to approach the lens from two different directions has been invaluable in cases with compromised zonules and posterior polar cataracts. Directing aspiration forceps away from areas of enhanced zonular integrity, rather than from areas of zonular weakness creates a scenario, that is much less likely to extend zonular dialyses or worsen lens subluxation. The ability to switch the irrigating chopper and the phaco needle between the two incisions is also helpful when lens material cannot be rotated to the distal location for efficient aspiration and phacoemulsification. In posterior polar cataracts, the ability to approach and aspirate all the lens material without rotating the endonucleus or epinucleus, minimizes the chances of placing undue stress on the fragile or compromised posterior capsule, which would result in posterior capsule rupture and vitreous loss. This capacity to switch handpieces during I&A of the cortex has

Fig. 6.70 Removal of subincisional cortex utilizing bimanual irrigation/aspiration system (Figure courtesy of Richard S. Hoffman)

simplified cortical clean-up, allowing for easy access to 360° of the capsular fornices and lowering the chances for capsular aspiration and tears during the removal of the subincisional cortex (Fig. 6.70).

6.8.3 Disadvantages

The disadvantages of biaxial microincision phacoemusificationarerealbuteasytoovercome.Maneuvering through 1.2 mm incisions can be awkward, early in the learning curve. Capsulorhexis construction requires the use of a bent capsulotomy needle or specially fashioned microincision forceps that have been designed to perform through these small incisions. Microincision capsulorhexis forceps is the best instrument for performing capsulorhexis and requires a small financial investment in the instrumentation. Although more time is initially required to learn to perform a capsulorhexis with these forceps, with experience, the maneuvers become a routine.

Also, additional equipment is necessary in the form of small incision keratomes, irrigating choppers and bimanual I/A handpieces. All of the major instrument companies are currently designing irrigating choppers and other microincision adjunctive devices such as capsulorhexis forceps. For the divide-and-conquer