In a recent letter to the editor of the Journal of Cataract and Refractive Surgery, Steve Arshinoff, MD, of Toronto, points out the incorrect application of several terms used to describe cataract extraction
by means of two paracentesis-type incisions.1
For example, he rightly notes that virtually all cataract surgeons use two hands during surgery, and therefore practice a
"bimanual" technique. He also eschews all relative terms describing incision size, since yesterday's small incision size rapidly
becomes today's large incision size, and "micro" will always connote "smaller than anything else, except nano."
Evolving terminology
Language often evolves in spite of logic rather than because of it. The application of the term "bimanual" to phacoemulsification
grew naturally out of its use in describing bimanual irrigation/aspiration (I/A), a technique that differs from monomanual
I/A in that it really does require two hands instead of one. The use of the term "micro incision" probably carries with it
a hint of the boast ("My incision's smaller than yours!") but it has nevertheless shown great tenacity. For better or worse,
bimanual micro incision phaco (BMMI phaco) and micro incision cataract surgery (MICS) are probably terms that are here to
stay. Unfortunately, they do not truly reflect the essential feature of the technique they have come to represent.
Takayuki Akahoshi, MD, of Japan,recently reported coaxial cataract extraction and IOL insertion through a 2-mm incision.2 Using a flared phaco tip and a small-diameter sleeve, he described pre-chopping and extracting the cataract, and then introducing
a single-piece AcrySof IOL through the unenlarged incision by placing the insertion cartridge tip just at the edge of the
incision and pushing the IOL through with the plunger. He bills this method as the "sayonara" technique, since he says it
will allow surgeons to say "sayonara, bimanual."
The underlying assumption, that BMMI phaco is only about incision size, demonstrates a superficial understanding of BMMI phaco
that relates directly to the unfortunate nomenclature that Dr. Arshinoff has criticized.
Only one aspect
In actual fact, reduction of incision size represents only one of many advantages that make BMMI a superior technique. The
crucial difference is not the size of the incision; it is the separation of inflow and outflow. We believe that the benefits of this fluidic paradigm shift include greater flexibility, improved control, and better outcomes.
At the same time, we recognize the significant role that the introduction of micro-pulsed ultrasound energy (WhiteStar technology,
Advanced Medical Optics) has played in setting the stage for bare-needle phacoemulsification. The use of extremely short pulses
of ultrasound energy with a variable duty cycle initially allowed safe BMMI phaco through elimination of the risk of thermal
injury to the cornea.
Separation of irrigation from the aspirating phaco needle allows for improved followability by avoiding competing currents
at the tip of the needle. In some instances, the irrigation flow from the second 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 refractive
lens exchange the lens material may be washed completely out of the bag and extracted with aspiration and vacuum only, so
that no ultrasound is used and no instrument enters the endocapsular space, increasing the safety profile of this demanding
procedure. The flow of fluid from the open end of an irrigator represents a very gentle instrument that can mobilize material
without trauma to delicate intraocular structures.
Further advantages
Figure 1. The stream of irrigation fluid from the open-ended irrigator on the left is directed toward the posterior capsule
while the silicone-sleeved aspirator is used to mobilize the plaque gently.
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Another benefit of a separate infusion stream comes to bear in scrubbing troublesome plaques from the posterior capsule (Figure
1). Focusing the flow of fluid on the posterior capsule and putting the tissue on stretch facilitates capsule polishing with
either a roughened or a silicone-covered aspiration tip. The taut posterior capsule shows less inclination to become entrapped
in the aspiration port, and the subcapsular plaque material is more easily stripped away.
Figure 2. Cortex that is subincisional to the left-handed incision can be easily reached from the right-handed incision.
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Perhaps the greatest advantage of the bimanual technique lies in its ability to remove subincisional cortex without difficulty.
As originally described by Brauweiler,3 by switching infusion and aspiration handpieces between two micro incisions, 360 of the capsular fornices are easily reached
and cortical clean-up can be performed quickly and safely (Figures 2 and 3). The ability to switch hands also represents a
significant advantage to instructors of phacoemulsification, who may find they must take over a case from a resident with
opposite manual dominance.4 Complication management
BMMI phaco also provides significant advantages in complication management. If the posterior capsule is compromised during
surgery, the first goal of the surgeon is to maintain stability of the anterior chamber to prevent both posterior migration
of lens material and anterior prolapse of the vitreous. By maintaining infusion high up in the anterior chamber, it becomes
safer to reach posteriorly with the phaco needle, aspiration tip, or vitrector to remove residual lens tissue. Irrigation
need never be brought down into the capsule where it may dislodge lens tissue, enlarge the capsular tear, or engage the vitreous.
Hypotony is avoided at all times by keeping the flow of irrigation constant, much in the same way that an anterior chamber
maintainer works.5
Figure 3. Difficult-to-reach subincisional cortex below the right-handed incision is more safely aspirated from the left.
The surgeon thus avoids potentially dangerous intraocular gymnastics that put the posterior capsule at risk.
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Once all lens material has been evacuated from the eye, viscoelastic may be injected prior to removal of the irrigator so
that the vitreous face remains under tamponade.
More stable environment
Utilization of BMMI phacoemulsification as we have described for refractive lens exchange and routine cataract surgery offers
an enormous advantage of maintaining a more stable intraocular environment during lens removal. This may be especially important
in patients with high myopia who are at a greater risk for retinal detachment following lens extraction.6 By maintaining a formed and pressurized anterior chamber throughout the procedure, there should be fewer tendencies for anterior
movement of the vitreous body with a theoretical lower incidence of posterior vitreous detachment occurring from intraoperative
manipulations. Future studies will need to be performed in order to document a significant reduction in posterior segment
morbidity utilizing this method of lens removal.
Figure 4. In this case of zonular dialysis a complete curvilinear capsulorhexis can be accomplished without loss of control
of the tear or vitreous prolapse thanks to the increased chamber stability seen by operating through a 1.2-mm incision with
specially designed forceps.
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Some of the major advantages we have seen from BMMI phaco do relate to incision size; for example, there has been an improvement
in control of most of the steps involved in endocapsular surgery due to increased chamber stability. Since viscoelastics 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.
Figure 5. Capsular dye and micro incisions facilitate the capsulorhexis for this intumescent cataract in a glaucomatous eye
status post implantation of a Baerveldt shunt. (Figures courtesy of Mark Packer, MD, FACS)
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This added margin of safety is particularly noticeable in cases of zonular compromise such as pseudoexfoliation, traumatic
zonular dialysis, and status post glaucoma filtering surgery, as well as in cases of intumescent cataract and nanophthalmos
with a very shallow anterior chamber (Figures 4 and 5).7 The added chamber stability can also make a difference in control of the capsulorhexis in high myopia with an extremely deep
anterior chamber and floppy capsule.
The adoption of micro incision techniques has also served as a catalyst for instrument manufacturers, who have developed delicate,
exquisite forceps for the construction of the capsulorhexis. The result has been unparalleled surgical control. Hydrodelineation
and hydrodissection can also be performed more efficiently by virtue of a higher level of pressure building in the anterior
chamber prior to eventual prolapse of viscoelastic through the micro incisions.
We have found this technique to be simple, efficacious, and safe since most of the lens extraction is occurring in the plane
of the iris, away from the posterior capsule and the corneal endothelium. Whether surgeons employ 18- or 21-gauge incisions,
the principal advantages of BMMI phaco arise from the separation of infusion and aspiration. No matter how small the incision,
these advantages cannot be achieved with coaxial techniques.
Mark Packer, MD, FACS
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Mark Packer, MD, FACS, is co-editor of Cataract Corner. He is assistant clinical professor of ophthalmology at Oregon Health & Science University, Portland, and is in private practice
in Eugene with Drs. Fine, Hoffman & Packer. 
I. Howard Fine, MD
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I Howard Fine, MD, is clinical professor of ophthalmology at Oregon Health & Science University, Portland, is a founding member of the Oregon
Eye Associates, and is in private practice in Eugene with Drs. Fine, Hoffman & Packer.
Richard S. Hoffman, MD
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Richard S. Hoffman, MD, is co-editor of Cataract Corner. He is clinical associate professor of ophthalmology at Oregon Health & Science University, Portland, and is in private practice
in Eugene with Drs. Fine, Hoffman & Packer. References
1. Arshinoff SA. Biaxial phacoemulsification. J Cataract Refract Surg 2005;31:646.
2. Technique allows IOL insertion through sub-2-mm incision after coaxial phaco. www.osnsupersite.com June 3, 2005.
3. Brauweiler P. Bimanual irrigation/aspiration. J Cataract Refract Surg 1996;22:1013-1016.
4. Smith JH. Teaching bimanual microincision cataract surgery in a residency program. Symposium on Cataract, IOL and Refractive
Surgery, ASCRS; April 19, 2005, Washington, DC.
5. Blumenthal M. Use and results using the new ACM. Symposium on Cataract, IOL and Refractive Surgery, ASCRS; April 18, 2005,
Washington, DC.
6. Colin J, Robinet A, Cochener B. Retinal detachment after clear lens extraction for high myopia: seven-year follow-up. Ophthalmology
1999;106:2281-2284.
7. Olson R. Viscoelastic to the rescue. In: Obstbaum SA, moderator. Advances in cataract surgery: devices, applications, techniques.
Ophthalmology Times Supplement 3, April 1, 2004;29:12-13.
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