32

Microphaco: Concerns and Opportunities

Randall J Olson

Introduction

Microphaco is a concept I define as completing cataract surgery through two stab incisions of 1.5 mm or less in size. True, microphaco in my mind however, is two stab incisions of no more than 1.0 mm. Microphaco can have as its energy source ultrasound, laser or sonic energy. While certainly not a new subject, removing soft lenses such as in pediatric cases through two stab incisions has a very long track record; it is just recently that there has been interest and enthusiasm in this approach. With the predominant power source for cataract removal being ultrasound, the concern about wound burn has been substantial and that has been one of the major sources for emphasis on laser or sonic energy to try to remove a cataract by microphaco.

The obvious first question one must ask prior to considering microphaco is the big one, “why do we need to consider a change”? Certainly our present cataract surgery through 2.5 to 3.0 mm incisions is well entrenched with great success and excellent postoperative results. Astigmatism change is minimal and the wounds are required to insert the present intraocular lenses. Simply removing a cataract through a smaller incision for no obvious net gain makes no sense. Progress is only progress if, indeed, doing something new adds to either the safety or the quality of our results.

In the past I felt that microphaco was unlikely to be advantageous; however, a series of issues have convinced me that this is a subject worthy of serious consideration. It is certainly obvious in very complicated cases where there have been an expulsive choroidal hemorrhage, that the smallness of the incision would be protective for the eye. In the present day, where we maintain positive pressure for most of the procedure, such complications are exceedingly rare and that in and of itself would not be reason enough to make a change. A second advantage, however, has to do with the ease of switching from one wound to the other in regard to using our aspiration (phaco) needle. Certainly complicated cases, either preoperatively complicated or complicated by the surgery, may result in difficulty completing the procedure safely due to the position of the complication. If our safe zone is right in the middle of our complicated area then switching the aspiration needle to the opposite wound produces an entirely new safe zone. This certainly has been understood as an advantage in regard to irrigation/aspiration. In present phacoemulsification techniques there are those who put in two stab incisions so they can do bimanual irrigation/ aspiration such that they can switch wounds and obviate any subincisional cortex problem and at the same time use the two instruments to manipulate removal of the cortex in a way that is simpler and safer than the standard coaxial approach. For me this was still not enough reason for me to want to proceed on this venture.

The main reason I moved into microphaco was the realization of what a problem irrigation is presently for us in traditional phacoemulsification. We have wrapped irrigation around our phaco aspiration needle to make sure that we have a cooling source

to avoid wound burn and to have plenty of irrigation to maintain the chamber. Certainly this has been very good in the prevention of wound burn, which is a very uncommon event, and also does a good job of maintaining the chamber. Irrigation surrounding aspiration has necessitated wounds of at least 2.5 mm and it is unlikely, due to the law of diminishing returns that we can go much smaller than that as long as we maintain a coaxial approach to our irrigation and aspiration. The problem is irrigation maintains our chamber but otherwise is not a positive force. Let me explain.

First of all some of the irrigation as it flows around the phaco needle is immediately aspirated and therefore does no practical work. This is very similar to an arterial-venous shunt in which the blood does nothing for the tissue just as shunted irrigant does nothing for our cataract surgery. Also, we have more flow than we need creating increased turbulence, which can be seen as lens fragments spinning and bouncing. Air bubbles and lens particles can damage the endothelium by this turbulence.

Furthermore, irrigation pushes nuclear fragments away right when we want to have the particles come to our phaco tip. This is quite apparent, clinically, as you watch nuclear fragments being buffeted and even pushed away by irrigation until you can finally move the phaco tip and find that aspiration vortex that sucks the particle back in. Larger fragments are often, besides being repulsed by the ultrasound, also pushed away by irrigation and all of this creates inefficiency. The other factor about irrigation is that when it is separated from irrigation it can be a positive force. You can use it to open the fornix so free nuclear fragments automatically flow to our phaco because this is the only exit if our wounds are tight. All of these irrigation advantages combined, if appropriately utilized in our microphaco technique, should significantly decrease the amount of fluid necessary and improve our efficiency and safety. These reasons in combination were the major impetus for me wanting to move forward in microphaco.

Prior to feeling comfortable with microphaco, it was critical to go to the lab to feel safe about this approach. My standard phacoemulsification technique being phaco chop has been ultrasound-assisted aspiration. Therefore to prove that microphaco was safe we, in a series of eye bank eyes, mounted a thermister right in the wound for continuous temperature monitoring.

With continuous ultrasound we determine how long it would take to create a wound burn. Indeed, 100 percent power with aspiration and irrigation separated created wound burn; however, it took several minutes and is only a minor concern. Our next phase, which was clamping the aspiration line, certainly increased the problem, however, it still occurred at 80 percent power and it took approximately one minute of continual power. Interestingly, when we did a pulse mode at 50 milliseconds (6 per second), we actually found less time was necessary in creating wound burn showing that just decreasing the energy alone may not be the answer. We still have not figured out exactly why this result (which was consistent with several eyes) occurred, but think it may be some type of harmonics which induces greater tissue energy buildup and a burn.1

These results left us cautiously optimistic that microphaco was safe if you used minimal amounts of ultrasound. Our original wounds were quite leaky and we recognize the room for error is even less trying to produce tight wounds. We cautiously started with microphaco and it was only when we realized that White Star (a new Allergan technology) could potentially diminish the risk of wound burn that we decided to

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duplicate our experiments using White Star with a duty cycle of one-third on and twothirds off.

White Star is a technology in which the ultrasound vibration can be turned off and on at levels of a millisecond or less. Previously such fine control had never been available, and therefore, there is an infinite number of modalities that can be used. Largely, an off cycle with very brief on cycles (about 20% on) enhances our ability to hold onto nuclear fragments and to remove them without chatter. It was also found that sculpting could be enhanced by this (usually 50% on and 50% off) with less energy utilized. Clearly, microchatter must occur in that particles are repulsed by ultrasound and then brought back by aspiration. This resulting in an inefficient use of energy which is obviated with White Star with very brief pulses of energy such that when the repulsion occurs the energy is off and energy is back on again when the item is aspirated. With all types of techniques used by a multitude of surgeons, the total energy utilized has been substantially less as one side benefit.

With microphaco we were mainly interested in claims of minimal energy heat transference. By putting a microthermister in the wound we repeated our eye bank studies and found that with 100 percent energy we never could get the temperature above 28°C, even after three minutes of continual energy! The temperature plateaued and we were confident that twenty minutes would not have made any difference. The second step was to block all aspiration that we found previously tremendously increased the risk of wound burn, and we certainly have found the same thing clinically. Even with aspiration blocked, the temperature never went above 32°C after three minutes of continual energy. We took this to the final stage in which we eliminated irrigation and just put a bare phaco needle in the wound. Even in this situation with 100 percent energy it took 29 seconds before we finally got a temperature elevation in the wound2! This technology is incredibly forgiving and now we have an ultrasound variant that gives us the flexibility of ultrasound and the elimination of wound burn risk. White Star ultrasound, therefore, became our focus for microphaco. This has since been duplicated in a clinical study where wound temperature averaged 30°C.3

We considered laser and sonic energy but were disappointed in the results of others,4–6 that showed they took longer to remove the cataract and neither modality was particularly effective in very hard nuclei. Our clinical experience with White Star was that it was equally efficacious on the hardest of nuclei as regular ultrasound and, therefore, we felt that we had the best of all worlds with lack of concern about wound burn.

Our clinical work has now proceeded for over one year with multiple issues discovered. It has been an interesting experience and I think that it would be best for me to categorize our experiences and concerns with each step of the procedure.

Initial Incisions

Certainly making two stab incisions should be no problem, however, the size of the incision is particularly important. If the incisions were created too large, the leak is too great and maintaining the anterior chamber is a big problem (Fig. 32.1). Furthermore, nuclear fragments come to the wound and not to our phaco needle obviating a major microphaco advantage. We have moved to 21 gauge technology largely because we

found this worked perfectly with our diamond blade, which makes an incision 0.8 mm wide. This results in a very tight incision but not too small that we can’t insert our instruments. The tightness of the wound helps maintain the anterior chamber and keeps lens fragments going to the phaco needle. For a

FIGURE 32.1 A large leak around the irrigating chopper (a rush of fluid can be seen above the chopper) results in anterior chamber shallowing and difficulty completing the procedure

20 gauge, the incision should be 1.0 to 1.1 mm and for 19 gauge between 1.3 and 1.4 mm. We found even 0.1 mm too large can result in difficulty with maintaining the anterior chamber and let too much flow around the instruments. The incision size is critical, too small and the wound is torn and tends to leak at the end of the procedure.

Location is also important in that we found we should insert the intraocular lens not through either incision, which will be discussed later. We kept them, therefore, at least 45° apart and left them between parallel to the iris surface and perpendicular to the eye and no longer than 1 mm. The length is critical in that the incisions being tight will oarlock our instruments and if they are too long can make the surgery more difficult. Also, anything other than almost parallel to the iris surface makes the incisions too long.

Capsulorhexis

Those who perform needle capsulorhexis will find microphaco incisions to be extremely simple such that a cystotome or bent tip needle works just fine. I prefer using forceps, and I had a difficult time finding forceps that work through a 21 gauge incision. Most small microincision forceps were too big. Finally, a 21 gauge forcep, while tight, was acceptable in completing my needle capsulorhexis

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FIGURE 32.2 A 23 gauge capsulorhexis forceps by ASICO makes work through a 0.8 mm incision a simple task

incision. A 23 gauge microcapsulorhexis forcep is now available from ASICO that will easily go through any of these incisions. The tip was originally too sharp and would cut the capsule easily; however, the latest modification has been a joy to work with (Fig. 32.2). The capsulorhexis should be similar in size and shape to whatever you normally do. However, I have been making my capsulorhexis smaller to make sure that it overlaps the edge of the intraocular lens which is optimal for prevention of after-cataract formation. This means the capsulorhexis should be well-centered and approximately 5 mm in diameter.

Hydrodissection/Delineation

Making sure that the nucleus will rotate is even more critical in microphaco than in regular phaco. Because the instruments are relatively tightly controlled by the incision, it is more difficult to manipulate the nucleus, therefore, free rotation is critical. I have found the Chang cannula where the tip can be impaled in the nucleus extremely helpful in guaranteeing easy rotation.

The other problem with hydrodissection and hydrodelineation is the smallness of the incision and making sure there is egress of fluid such that positive pressure is not produced to the point that the capsule or zonules are broken. Breaking the capsule or zonules is much easier to do than you might imagine, particularly with very high viscosity viscoelastics such as Healon 5. I make the fluid burst minimal and short but rapid. Irrigate as you go in so that there is a fluid egress channel around the cannula.

Anterior Chamber Maintenance

This continues to be a major problem with microphaco. Irrigation through a 21 gauge cannula requires unimpeded flow in order to maintain the chamber. Wounds that are too

large leak too much and a stable chamber is very problematic. Furthermore, the cannula openings must be as large as possible with a single open end, the best option, which also best utilizes irrigation as a positive directable force. Unfortunately, it also leaves little strength on the end to mount a tip for chopping, etc. The second option we have used is two oval holes as large as possible and as far forward as possible on each side of the cannula to guarantee adequate flow. The cannula must be very thin walled and utilize a large hollow handle in which the irrigation line can be directly inserted. Furthermore, I put the irrigation bottle on an IV pole to raise it as high as possible. Dr. Agarwal has pressurized the line to try to enhance anterior chamber maintenance. Our experiments with the bottle at normal height showed large fluctuations in the intraocular pressure up to 55 mmHg. My concern is that a constantly pressurized line could result in extremely high pressures that may be dangerous to the optic nerve or could push the lens back if it is trapped by the iris and causes zonular damage.

The solution to this would be an irrigation line that has positive pressure assistance to maintain the pressure level at no less than 22 mmHg. I am sure such a pressurized system will be available soon. Whatever instrument you use, and I have seen many proposed lately that clearly will not maintain enough flow to maintain the chamber, should be tested. It is simple to set the bottle at your working height and if you don’t have at least 40 ml of fluid flow in one minute at free flow, then reconsider using that instrument!

FIGURE 32.3 “Oar-locking” by a tight wound makes use of the irrigating chopper on the left hemi-nucleus a difficult task. Nucleus rotation is critical here

Nucleus Removal

Nucleus removal using White Star with microphaco is no different than any other techniques you may have used. My preference is vertical or horizontal chop and divide and conquer works well. There are, however, some notable differences with which you must become accustomed. The first is already mentioned and that is the oarlocking, which makes movement of the irrigation instrument and the aspiration needle somewhat

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more difficult (Fig. 32.3). It is important to use the utility of the two instruments such that between the two, all areas of the chamber can be covered. Simple irrigation will move nuclear fragments to the safe zone. The importance of nucleus rotation will become apparent once you start removing the nucleus.

The second difficulty has to do with the weight of the instrument, which is noticeably heavier and stiffer due to the irrigation line. It will not feel as manipulable as second instruments you have used. My experience is this only takes a little time to get used to and is not a major problem. All of these issues are compounded very much if there is not good anterior chamber (AC) maintenance, and I am convinced in talking to others that AC stability is the biggest problem they are running into and not the actual nucleus removal technique.

Microphaco is tailor-made for vertical chop. In vertical chop it is important to move the sleeve back as far as possible. One of the first things you will find about microphaco is that the sleeve mechanically blocks all penetration and that with the absence of the sleeve your cutting will be much faster and much better. At first this was a little shocking and I am sure if the surgeon is not careful you could easily penetrate the nucleus (fortunately, I have not done this in nucleus removal to date). With vertical chop in microphaco, the phaco needle easily cuts into the nucleus with no sleeve to block it. Taking an irrigating chopper with a classical approach in the capsular fornix or lodged in the nucleus can result in loss of flow with AC shallowing. Such is never necessary with vertical chop in which the irrigating openings are always above the nucleus. I feel microphaco vertical chop will come to be the superior technique.

Bimanual Irrigation and Aspiration

Having two instruments has already been seen by many as a distinct advantage. The irrigating instrument and irrigation flow can open the capsular fornix and retract the iris, making aspiration a snap. Subincisional cortex is removed by switching the two instruments, which also works in creating a new safe zone should there be a problem (Figs 32.4A and B).

Cortex removal is two-handed, and again the problem is anterior chamber maintenance. If you have a 20 gauge incision to start with and then use 21 or 23 gauge bimanual irrigating/aspirating instruments, you will not maintain the chamber because your leak is too great. Your irrigation/ aspiration instruments should be the same size as your original phaco instruments.

Intraocular Lens Insertion

Neoptics has a lens that has been put through a 1.5 mm incision. Other approaches will take advantage of microphaco-type incisions. At present, however, the majority of microphaco surgeons are enlarging the wound to insert an intraocular lens. There are multiple ways to put the lens in; however, I found that making a totally

FIGURES 32.4A AND B Switching the irrigating and aspirating instruments from the regular position

(A) to an aspiration right position (B) eliminates the sub-incisional cortex problem

separate incision for the lens was best in that it was easiest to seal this wound (Fig. 32.5). This does create some difficulty for final irrigation and aspiration such that you can either use a typical coaxial system to remove the viscoelastic or, if you want to continue the bimanual approach, then you must hydrate your intraocular lens wound or you will get too much leakage from this wound and you will have difficulty in maintaining the anterior chamber.

Closure of Microphaco Wounds

This has turned out to be a problem in microphaco and, in particular, when I made my intraocular lens wound centered on one of the two stab incisions. It

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FIGURE 32.5 If a regular foldable implant is to be used, I make a separate incision with a diamond keratome to facilitate wound closure

turns out that microphaco by putting our instrument through a very small and tight wound results in stretching of the tissue and they tend to continue to leak. I had great difficulty in getting these to seal and had to put a suture through several, which occurrence had been exceedingly rare in the past. It turns out hydration of the edges of the wound does not effect the original stretching that was in the center of the wound and this was the reason I encountered difficulty. By making a separate intraocular lens wound and never having manipulated or stretched it with phacoemulsification steps allowed spontaneous sealing to occur even more often than usual.

The two stab incisions, however, will not spontaneously seal. I aggressively stromal hydrate both stab incisions and found that getting a 19 gauge wound to seal was very difficult while it was much easier with a 21 gauge wound. If it continues to leak, stromal hydration directly in the center, either posteriorly or anteriorly, may work. Usually stromal hydration does the trick. If it does not, invariably this is an incision where you had to work to force the instrument in (usually the irrigating instrument) and therefore stretched the wound. Understanding this problem is important in instrument development.

An additional approach I have found successful is to make the stab incision on the edge of the phaco wound so that stromal hydration closes this wound more easily. In talking to others however, getting the wounds to close is clearly a disadvantage. We will develop technology to obviate this issue. Making the original incisions large enough so that you don’t have to stretch them is not effective due to the anterior chamber maintenance problem secondary to the leak. Maintaining positive fluid flow in the face of some leaking will certainly help the anterior chamber maintenance problem but not the problem of nuclear particles coming to the wound and not to the phaco tip.

In summary, microphaco is a technique that is evolving and to take advantage of the newer, smaller intraocular lenses that will be coming soon everyone will have to move to microphaco. It is slightly more difficult; however with experience, success is achievable. Twenty-one gauge technology has made it a little slower due to the smallness of the phaco needle bore; however, 20 gauge technology is just as fast as regular phaco. The irrigation advantages I have found to be real with basically the same sense of speed using

one-third less irrigation. White Star will safely work with the densest cataracts as another significant advantage.

As this technology evolves not only will it take advantage of the new intraocular lenses that can go through such small incisions, it may also prove to be safer with the irrigation advantage, the opportunity to switch wounds and by obviating the need to chase lens fragments with the ultrasound needle. In the meantime stay tuned to an interesting and evolving approach to cataract surgery.

References

1.Soscia W, Howard JG, Olson RJ: Bimanual phacoemulsification through two stab incisions: A wound temperature study. J Cataract Refract Surg 28:1039–43, 2002.

2.Soscia W, Howard JG, Olson RJ: Microphacoemulsification with White Star: A woundtemperature study. J Cataract Refract Surg 28:1044–46, 2002.

3.Donnenfeld ED, Olson RJ, Solomon R, et at: Efficacy and Wound Temperature Gradient of White Star Technology Phacoemulsification Through a 1.2-mm Incision. J Cataract Refract Surg; submitted

4.Kanellopoulos AJ: Laser cataract surgery. Ophthalmology 108:649, 2001.

5.Dodick JM: Laser phacolysis of the human cataractous lens. Dev Ophthalmol 22:58–64, 1991.

6.Alzner E, Grabner G: Dodick laser phacolysis: Thermal effects. J Cataract Refract Surg 25:800– 03, 1999.

33

Ultrasmall Incision Bimanual Phaco

Surgery and Foldable IOL

HiroshiTsuneoka

Introduction

The increasing use of phacoemulsification and aspiration (PEA) and the advent of foldable intraocular lenses (IOLs) have been accompanied by dramatic advances in the field of cataract surgery. Some ophthalmologists even suggest that this technology may be reaching its peak, with fewer developments to be expected in the future. However, a number of problems remain to be resolved.

One of these problems involves the need for further improvement in postoperative visual acuity. Although the availability of IOLs has increased the likelihood of a good outcome, numerous problems remain regarding lack of accommodation, glare, deterioration in contrast sensitivity, and changes in color perception.

A second problem is the need for less invasive surgery. At present, cataract surgery can be performed through an incision of 3–4 mm, and surgical procedures are under development which will make it possible not only to remove the clouded lens through an ultrasmall incision of approximately 1.0 mm, but also to insert the IOL without enlarging that incision.

Ultrasmall-incision cataract/IOL surgery requires not only improved techniques for lens extraction, but also the development of IOLs which can be inserted through these ultrasmall incisions. Many companies are currently working to develop IOLs which can be inserted through an incision of less than 2 mm, and a number of these products are expected to be on the market soon.

Regarding lens extraction, considerable attention has been directed in recent years to new emulsification and aspiration techniques using the erbium YAG laser and the neodymium YAG laser. This technology provides numerous advantages, including the absence of heat generated during phacoemulsification and minimal invasiveness of the cornea of the capsular bag, and is expected to drive the next generation of cataract surgery technology. However, it is not yet widely used because it currently takes longer than phacoemulsification for nucleus removal. Recently AJ Kanellopoulos and JM Dodick have reported on the results of bimanual laser phaco surgery using a Q-switched neodymium YAG laser.1 They state that by improving laser surgery equipment and surgical techniques it is possible to dramatically reduce operating time, and that a dehydrated and folded acrylic IOL can be inserted through an incision of 1.6 to 1.8 mm after YAG laser surgery. However, in contrast to the PEA equipment which is in wide use today, laser phaco machines still have considerable room for improvement before the technology will be fully matured, so we expect that it will be some time yet before these

procedures become widely available. There is also some question about how well this new IOL material will stand up over years of use.

Since 1999 we have been studying the use of PEA, a mature technology with highly reliable equipment, for lens extraction through an ultrasmall incision. We have used this equipment to perform basic research on lens extraction through an incision of 1.4 mm or less,2 and have also developed a new type of foldable acrylic lens which can be inserted through these incisions. The present article will address ultrasmall incision cataract surgery using surgical equipment, surgical techniques, and IOL materials which are widely available today.

Basic Research on Ultrasmall Incision Cataract Surgery Using Phaco Machines

Use of the Sleeveless Phaco Tip Enables Ultrasmall Incision Cataract

Surgery

In ordinary PEA, the pahco tip is equipped with an infusion sleeve. In order to reduce incision size, it has been necessary to decrease the outer diameter of the infusion sleeve. Phaco machines in current use require an incision of at least 2.6 mm even when using a thin phaco tip. In order to successfully utilize surgical incisions of less than 2.0 mm, the infusion sleeve must be removed to leave the sleeveless phaco tip, with infusion provided through a side port.

In order to use the sleeveless tip safely it is necessary to ensure that adequate infusion is provided through the side port, that the phaco tip does not overheat during emulsification and aspiration, and that there is no deformation of the incision due to movement of the tip.

History of PEA Using a Sleeveless Phaco Tip

In 1984, Hara and colleagues began using a sleeveless phaco tip in intracapsular phacoemulsification and aspiration for lens refilling.3 The technology attracted considerable attention, particularly in the United States, but procedures for lens emulsification and aspiration at that time were quite difficult and no suitable lens refilling material was available, so the method was never widely adopted.

Fifteen years later, in 1999, we began working with bimanual PEA using a sleeveless phaco tip in order to reduce incision size during cataract surgery. We first performed basic research to make sure that the surgery would be safe, determining the feasibility of bimanual nucleofractis with infusion through a side port, establishing methods for ensuring adequate infusion flow volume, and investigating techniques to prevent thermal burn and deformation at the incision site. We then applied these findings in a clinical setting to develop procedures for lens extraction through a 1.2 to 1.4 mm incision.2

Prior to this, in 1998 A Agarwal and colleagues reported4 successful lens extraction through a 0.9 mm incision using the Phakonit method with a sleeveless phaco tip. Under this method thermal burn is avoided by providing external irrigation of the incision through which the ultrasound probe is inserted.

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At almost the same time P Crozaf on reported the successful use of a sleeveless 21 gauge Teflon-coated tip for minimally invasive bimanual PEA through a 0.9 mm incision. Crozafon felt that thermal burn could be prevented by coating the phaco tip with Teflon, which has poor thermal connectivity.

In 2001 R Olson reported the feasibility of PEA through a 1.0 mm incision using the new PEA machine, Sovereign (Allergan), with White Star software. Olson found that tip heating could be minimized by setting the machine for pulse mode so that ultrasound was generated for extremely short intervals.

In our ultrasmall incision cataract surgery we use a relatively large incision of 1.2 to 1.4 mm. We find that when the incision is slightly larger than the phaco tip, the tip can be cooled by the leakage of infusion solution through the incision, and the extra space also prevents deformation at the incision site due to tip movement.

Problems Related to PEA with a Sleeveless Tip

Major problems when using a sleeveless tip for PEA include thermal burn at the incision site because of overheating of the phaco tip, and destabilization of the anterior chamber due to inadequate infusion flow. Also, the necessity of providing infusion through the side port means that the traditional nucleofractis hook cannot be used. Many surgeons have been particularly concerned that ultrasound waves through the sleeveless tip could cause a sudden rise in tip temperature, resulting in thermal burn at the incision site, and that the sleeveless phaco tip would, therefore, be unfeasible for emulsification of hard nuclei where the tip is sometimes fully occluded. To resolve these concerns, we measured incision site temperature in postmortem porcine eyes during phacoemulsification with full occlusion of the phaco tip. Our experiments confirmed the absence of thermal burn when using a 20 gauge sleeveless phaco tip through an incision made by a 19 gauge microvitroretinal (MVR) blade. We also modified a 20 gauge infusion cannula and inserted it through a side port created with a 20 gauge MVR. The cannula modifications ensured adequate infusion flow, stabilizing the anterior chamber, and also made it possible to use the infusion cannula as a nucleofractis hook. This allowed us to safely emulsify and aspirate nuclei with conventional bimanual nucleofractis techniques, and enabled us to confirm the feasibility and safety of PEA through an incision of 1.2 to 1.4 mm using familiar techniques and widely available surgical equipment.2

Avoid Thermal Burn and Injury at the Incision Site: Widen the Incision by 1 Gauge

We believed that if the incision was made slightly wider than the outer diameter of the phaco tip, the tip would be satisfactorily cooled by the leakage of infusion solution through the incision, preventing thermal burn at the incision site. To test this hypothesis we measured temperature at the incision site in postmortem porcine eyes during phacoemulsification.

The PEA device used in our experiments was the Alcon Legacy 20000® with a 20 gauge Kelman phaco tip (manufactured by Alcon Laboratories, Inc). Temperature at the incision site was measured with a sheathed thermocouple Model TSC-K0.3 manufactured

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the incision site in postmortem porcine eyes. Phaco machine setting: Aspiration port occluded (aspiration pressure: 0 mmHg). US power: 80%, US duration: 2.0 min continuous. (A left) A 20 gauge Kelman U/S tip with the infusion sleeve was inserted through a 3.0 mm incision, and US were operated. Temperature at the incision site rose only slightly while the tip was kept from pressing on the incision wall. But, once the tip was pressed against the incision wall during US operation, the temperature at the incision site rose significantly and a thermal burn developed. (B right) A 20 gauge Kelman U/S tip without the infusion sleeve was inserted through a 19 gauge incision, and US were operated. Temperature did not rise at the incision site even when the tip was pressed against the incision, and no thermal burn developed

When the phaco tip is not fully occluded in PEA, the tip lumen and outer wall are bathed in infusion solution, so that even when friction develops there is a sufficient flow of infusion solution to cool the tip. However, in phacoemulsification with full occlusion the infusion solution is ordinarily unable to circulate within the phaco tip, so the amount of infusion solution in contact with the outer wall of the tip is limited to the volume of solution passing through the incision site. During fully occluded nucleofractis with a phaco tip equipped with an infusion sleeve, there is a decrease in the volume of infusion solution flowing around the tip. If the tip should press against the incision wall under these circumstances, the infusion solution may not provide sufficient cooling to compensate for the friction heat generated by the tip and sleeve. This can result in the development of thermal burn at the incision site (Figs 33.2A and 33.3A). However, when using a sleeveless phaco tip in an incision which is slightly larger than the tip itself, there is still considerable leakage of infusion solution through the incision site even during fully occluded phacoemulsification when the tip may be moved in multiple directions and pressed against the incision in order to emulsify the nucleus. This leakage of infusion solution provides sufficient cooling of any friction heat which may develop between the tip and the surrounding tissue, making it possible to emulsify and aspirate the nucleus

without the occurrence of thermal burn and without resorting to Teflon-coated phaco tips or ultrasonic wave-control technology (Fig. 33.3B). By implementing this technique, thermal burn is less likely to occur when using a sleeveless tip than when using a tip equipped with the infusion sleeve.

When we perform bimanual PEA, one of the main points in our surgical technique involves the use of an incision which is 1 gauge larger than the outer diameter of the phaco tip. This means that the incision for a 20 gauge phaco tip is made using a 19 gauge (1.4 mm) MVR, and for a 21 gauge phaco tip we used a 20 gauge (1.2 mm) MVR. The slight space between the phaco tip and the incision wall prevents deformation and injury at the incision site due to movement of the phaco tip.

Tools for Successful Bimanual PEA: The 20 Gauge Irrigating Chopper (Fig. 33.4)

The goal of bimanual PEA is to remove the nucleus through the smallest incision possible. In addition, it is desirable to use only a single corneal side port,

FIGURES 33.3A AND B Flow dynamics of infusion solution around the phaco tip when the opening of the tip was closed during occlusion mode. (A left) Emulsification and aspiration following insertion of a sleeved phaco tip through a 3.0 mm incision. Because the sleeve is deformed by contact with the incision, leakage volume through the incision is low. During phaco tip fully occluded in PEA, the flow of infusion solution around the phaco tip within the infusion sleeve is also low. When the phaco tip pressed against the incision wall, friction heat develops

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between the tip and the sleeve. Because there is insufficient infusion solution flowing around the tip to provide cooling, the heat is transmitted to tissues at the incision site. Thermal burn develops at the incision. (B right) Emulsification and aspiration following insertion of a sleeveless 20 gauge phaco tip through a 19 gauge (1.4 mm) incision.

Because the phaco tip is not deformed by passage through the incision, there is space between the tip and the incision. Thus, the maximum possible volume of infusion solution is available to flow around the tip, providing cooling for any friction between the tip and the incision tissue. No thermal burn develops at the incision site

and to make that port as small as possible also. Creating a third incision for the nucleofractis hook would run counter to the objectives of this surgical technique. With that in mind, we experimented with a bend in the tip of the infusion cannula. This resulted in the production of hooked infusion cannulae having nearly the same shape as conventional nucleofractis hooks. The Tsuneoka Irrigating Hook and the Tsuneoka Irrigating Chopper are manufactured by American Surgical Instruments Corporation (ASICO).

When using the infusion cannula as a hook or chopper, considerations of intraocular operability dictate that instrument size not exceed 20 gauge. However, an ordinary cannula having a 20 gauge outer diameter would have an inner diameter of only 0.6 mm, making it difficult to guarantee

FIGURE 33.4 The 20 gauge irrigation cannula with nucleofractis hook. A cannula was prepared having an outer diameter of 0.9 mm and an inner diameter of 0.7 mm, with large aperture at the tip. The cannula walls were made thinner to ensure adequate flow of infusion solution. This cannula, manufactured by ASICO Co, Ltd, is an essential tool for use in the procedure described here

adequate infusion volume. With the infusion bottle at a height of 110 cm, an inner diameter of 0.6 mm would permit a flow volume of only 38 mL/min. This is not enough to sustain anterior chamber depth during surgery. We thus reduced the thickness of the infusion cannula wall to yield an inner diameter of 0.70 mm. The modified cannula provides a flow rate of 50 mL/min when the infusion bottle is raised to 110 cm.

The hook at the tip of this cannula is shaped to provide excellent operability during emulsification and aspiration. Stable anterior chamber depth is maintained during PEA, and the hook works well in a variety of nucleofractis procedures.

Equipment for Safer Bimanual PEA: The GFX Unit and VGFI Tubing (Fig. 33.5)

In order to safely perform this surgery, it is important to increase the depth of the anterior chamber during emulsification and aspiration. In cases where destabilization of anterior chamber depth occurs during PEA even with the infusion bottle elevated to 110 cm or higher, it is advisable to increase the flow rate by applying pressure to the infusion bottle. During lens extraction we use a GFX fluid-gas exchanger, manufactured by Alcon Laboratories, Inc, with vented gas forced infusion (VGFI) tubing. Applying a pressure of 10 mmHg

Phacoemulsification 486

FIGURES 33.5A AND B GFX (Gas Fluid Exchange) equipment and VGFI (Vented Gas Forced Infusion) tube an air pump of GFX equipment (A) creates pressurized air, and VGFI tubing (B) delivers it to the infusion bottle. Fluid from the infusion bottle creates the same pressure and improves anterior chamber stability of patient eye. Infusion flow rate can be automatically controlled with the GFX air pump without raising or lowering the bottle

to the infusion bottle has the same effect as raising the bottle an additional 13 cm, and makes it possible for us to increase the infusion flow to the specific extent required. Agarwal and colleagues5 also use the technique of applying pressure to the infusion bottle in order to stabilize anterior chamber depth.

Clinical Results of Ultrasmall Incision Cataract Surgery Using PEA

Results from our experiments indicated that thermal burn could be prevented by obtaining

FIGURE 33.6A A temporal corneal incision is made using a 19 guage MVR

sufficient leakage through the incision, and that a hooked infusion cannula (the Tsuneoka Irrigating Hook, manufactured by ASICO) can be used to emulsify and aspirate nuclei by bimanual nucleofractis while maintaining stable anterior chamber depth. In October 1999 we began applying these procedures to ultrasmall incision phaco surgery in human patients.

Procedures for Ultrasmall Incision Bimanual Phaco Surgery6

After the eye is anesthetized, we make an incision from the temporal clear cornea into the anterior chamber. We use a 19 gauge MVR blade for a 20 gauge small tip or a 20 gauge blade for a 21 gauge microtip (Fig. 33.6A). The incision is approximately 0.9 mm in length. We also create the infusion side port at a desirable location on the clear cornea, using a 20 gauge MVR blade (Fig. 33.6B). Sitting at the patient’s head, the surgeon positions the side port at eleven O’clock for the left eye or at one O’clock for the right eye.

Injecting a viscoelastic material into the anterior chamber, we use a 26 gauge needle to perform continuous curvilinear capsulorrhexis (CCC) with a diameter of approximately 5.0 mm, and then initiate hydrodissection. In order to prevent an abrupt rise in anterior chamber pressure, it is important to press the base of the hydrodissection

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FIGURE 33.6B A side port for irrigation is made at 1 O’clock in the right eye using a 20 gauge MVR

needle firmly against the lower side of the incision so that excess fluid can leak out of the incision while injection is in process.

We insert the Tsuneoka Irrigating Hook through the side port and the sleeveless phaco tip through the temporal corneal incision, and emulsify and aspirate the lens while using the tip of the cannula for nucleofractis (Fig. 33.6C). When we are working on the right eye we hold the irrigating hook in the left hand and the ultrasound probe in the right hand, and when working on the left eye we do the reverse, with the irrigating hook in the right hand and the ultrasound probe in the left hand.

We use bimanual nucleofractis when emulsifying and aspirating the nucleus. Depending on nucleus hardness, we use choose between the divide and conquer, quick chop (karate chop), or crater divide and conquer methods (Fig. 33.6D). Safe PEA requires that stable anterior chamber depth be maintained during surgery to prevent collapse of the anterior chamber, and that scattering of nuclear fragments be avoided. In order to maintain anterior chamber depth, a careful balance must be maintained between the settings for side port infusion and for phaco tip aspiration. We adjust the height of the infusion bottle to provide a side port infusion flow rate of at least 50 mL/min when using a 20 gauge phaco tip, and an infusion flow rate of 40 mL/min for a 21 gauge phaco tip. It is also important to set the parameters of the PEA

FIGURE 33.6C A 20 gauge sleeveless phaco tip is inserted into the anterior chamber through a 19 gauge incision and a 20 gauge Tsuneoka irrigating hook is inserted through a 20 gauge side port

FIGURE 33.6D PEA is performed using bimanual nucleofractis technique

machine appropriately, particularly the values for aspiration flow rate and maximum aspiration pressure. The settings used at our institution are shown in Table 33.1.

Infusion flow may not keep up with aspiration flow if aspiration is continued when there are no nuclear particles to be captured by the aspiration port on the phaco tip. Surgery can be performed more safely if aspiration is turned off when it is not needed.

Prevention of nuclear fragment dispersion is an important point for improving PEA safety. It is important to turn the ultrasound power as low as is feasible in order to reduce the extent of endothelial injury from nucleus “kick”. Great care must also be taken when using the nucleofractis hook to handle nuclear fragments.

TABLE 33.1 Parameters used by phaco machine type

FIGURE 33.6E Residual cortex is aspirated using a sleeveless I/A tip or 23 gauge bimanual I/A tip through the side port

FIGURE 33.6

Ultrasmall incision (1.4 mm) bimanual phaco surgery

Aspiration of the residual cortex through an ultra-small incision can be performed using a sleeveless I/A tip or a 23 gauge aspiration cannula through the side port (Fig. 33.6E). In cases where it is difficult to remove endothelial fragments below the incision line, the positions of the infusion cannula and the aspiration tube can be reversed so that this procedure can be performed safely and effectively.

Perioperative and Postoperative Results

Results of Surgery

Since October 1999, ultrasmall incision PEA surgery has been performed at the Jikei University School of Medicine Hospital by 3 surgeons on 757 eyes. Mean operating time is 8 minutes 42 seconds, comparable to the time required for conventional cataract IOL surgery by PEA. Approximately 90 mL of infusion solution is required per surgery, slightly more than that for conventional procedures. Both operating time and amount of infusion solution increase with greater nucleus hardness.

Incidence of Perioperative Complications

Among the patients studied, posterior capsular rupture occurred without vitreous prolapse in 3 eyes (0.4%), and with vitreous prolapse in 6 eyes (0.8%). However, none of these incidents of posterior capsular rupture were caused by use of this technology, and all were treated successfully with uneventful recovery.

Nuclei having a hardness of grade 4 or above (Emery-Little classification) were encountered in 37 eyes. No thermal burn developed in any of these cases, even though the use of ultrasound was prolonged.

Postoperative Course

Slight iris injury developed in 6 eyes (0.8%) which showed preoperative shallow anterior chamber and in 6 eyes (0.8%) with small pupils. There were no other notable postoperative complications.

Postoperative follow-up was continued for at least 3 months in 312 eyes. Greater nuclear hardness was associated with higher rates of reduction in endothelial cell density (4.1±12.3% for nuclei of hardness grade 1 or 2, 10.8±16.0% for grade 3, and 16.8±12.6% for grade 4 and above). However, none of these results differed greatly from those for conventional techniques.

IOL Insertion through an Ultrasmall Incision

New IOLs for Use with Ultrasmall Incisions

In current cataract surgery even though the cataract can be removed through an incision of 1.2 to 1.4 mm, there are no commercially available IOLs which can be inserted through such a small incision, so at present the incision must be enlarged to 2.8 to 4.1 mm before the IOL can be inserted. However, several companies are developing acrylic soft lenses which are thinner than the current commercially available foldable IOLs, and in the near future we can expect to see the marketing of IOLs which can be inserted through an incision of 1.4 mm or less.

At present Kanellopoulos and colleagues have reported the insertion through a 1.6 mm incision of a dehydrated acrylic IOL manufactured by Acri Tec GmbH (Germany), and

SA30AL and MA30BA) through a 2.2 mm incision (Fig. 33.7A).

We set the AcrySof® SA30AL (Fig. 33.7B) or MA30BA (Fig. 33.7C) in the Monarch IIC cartridge, place the cartridge loaded with the IOL into the injector, and press the plunger forward while ensuring that the pressure is applied to the optic portion of the lens.

During insertion, the front tip of the cartridge is inserted into the corneal incision so that it presses against the incision wall. The cartridge tip does not enter the anterior chamber. Immediately before inserting the lens, we instruct the patient to look steadily in the direction of the incision. With the

FIGURE 33.7C AcrySof® MA30BA is inserted through a 2.2 mm incision

FIGURE 33.7D The final incision size is measured using Tsuneoka ultrasmall inner caliper

cartridge tip elevating the inner edge of the corneal incision and pressing down on the outer edge, we slowly press the injector plunger forward. With a hook inserted through the side port, and making sure that the eye is not turned inward toward the nose, we continue to press the plunger forward without decreasing the downward pressure of the

The AcrySof® MA30BA and SA30AL lenses, currently the most widely used hydrophobic acrylic lenses in the world, are normally inserted through an incision of 3.0 mm or above. Our method makes it possible to insert these lenses through a 2.2 mm incision (Fig. 33.8), which increases the significance of ultrasmall incisions for lens removal. In our experience this lens removal surgery can be most effectively performed by bimanual PEA using a sleeveless phaco tip.

References

1.Kanellopoulos AJ, Dodick JM, Brrauweiler P: Dodick photolysis for cataract surgery. Ophthalmology 106:2197–2202, 1999.

2.Tsuneoka H, Shiba T, Takahashi Y: Feasibility of ultrasound cataract surgery with a 1.4 mm incision. J Cataract Refractive Surg 27:934–40, 2001.

3.Hara T, Hara T: Clinical results of phacoemulsification and complete in-the-bag fixation. J Cataract Refractive Surg 13: 279–86, 1987.

4.Agarwal A, Agarwal A, Agarwal S et al: Phakonit: Lens removal through a 0.9 mm corneal incision. J Cataract Refractive Surg 27:1548–52, 2001.

5.Agarwal S, Agarwal A, Sachdev MS, et al: Air pump to prevent surge. In: Agarwal Set al (Eds):

Phacoemulsification, Laser Cataract Surgery and Foldable IOLs (2nd ed). Jaypee Brothers: New Delhi, 2000.

6.Tsuneoka H, Shiba T, Takahashi Y: Ultrasonic phacoemulsification using a 1.4 mm incision: Clinical results. J Cataract Refractive Surg 28:81–86, 2002.