Ординатура / Офтальмология / Английские материалы / The Art and the Science of Cataract Surgery_Boyd, Barraquer_2000

Cartridge Injector Systems

Some of the newest advances in lens insertion technology surround the use of cartridge injector systems. Fine, Lewis and Hoffman believe that there are many perceived advantages of implanting foldable IOLs with injector systems, as compared with folding forceps. These advantages include the possibility of greater sterility, ease of folding and insertion, and implantation through smaller incisions.

Greater sterility with injector systems is believed to occur because the IOL is brought directly from its sterile package to its sterile cartridge and inserted into the capsular bag without ever touching the external surface of the eye, as is the case for lenses in folding forceps. Although this advantage would suggest a lower rate of endophthalmitis with injector systems, recent clinical studies have shown no significantly different rate of bacterial contamination of the anterior chamber after implantation of silicone lenses with a forceps versus an injector.

Perhaps the most appealing advantage of injector systems is that the lens can be loaded by a nurse or technician without the use of an operating microscope, further streamlining the procedure. Inaddition,insertingfoldablelenses with a cartridge device is generally felt to be easier than insertion with forceps, and these lenses can usually be implanted through a smallerincisionwhendeliveredbymeansofan injector, compared with an insertion forceps.

Allergan's foldable three piece silicone lens (monofocal or multifocal - AMO Array) with PMMA haptics may be implanted with AMO's Unfolder Phacoflex injector system. Allergan's acrylic foldable IOL (Sensar and Clariflex lenses) may be implanted with a new injector now available and known as the

Unfolder Sapphire, as described by Centurion (Fig. 82-A). These injectors are resterilizable (as are the forceps, of course).

Alcon’s popular 5.5 mm AcrySof IOL may be implanted with one of its injectors such as the Monarch (Fig. 82) or with a standard cartridge through a 3.0 mm incision. Some have reported injecting this lens through a 2.8 mm incision. Many surgeons use Alcon’s Acrypack (Fig. 82) when implanting the AcrySof lenses. The Acrypack serves to first fold the IOL. The surgeon then uses a forceps (Fig. 81) to implant the already folded IOL.

The Alcon AcrySof lens, which requires 3.5 to 4.0 mm incisions for 6.0 mm optics and 3.2 to 3.5 mm incisions for 5.5 mm optics, is now packaged in a wagon wheel dispenser. The easiest folding instrument to use for these lenses is the Rhein folder, because its tips have been extended to make it easier to remove the lens from the wagon wheel package. The forceps can be turned with the tips down in the nondominanthand. Thetipsgointotheslotson both sides of the optics, so that the lens can be picked up and placed on a drop of viscoelastic. The forceps are then turned so that the tabs are down. The lens is grasped and folded, and then the insertion device in the dominant hand is used to insert the lens.

THE PHACO PROBES AND TIPS

In Fig. 83 you can see two different types of phaco probes and tips. In Fig. 83 (left), there is a larger caliber probe with a straight tip. This is particularly used when the incision is predominantly limbal. The incision is slightly larger than the one mostly utilized today which is the corneal incision shown in Fig. 83 (right). The probe in Fig. 83 (left) using a standard

phaco tip emits more heat which could harm the corneal lips. The phaco probe and tip, shown in Fig. 83 (right), is narrower and can, therefore, be utilized in smaller corneal incisions such as the 2.6 mm shown in Fig. 83 (right). The popular angled Kelman tip shown here has a high capacity to cut the tissues and is very useful in more dense cataracts. It allows the use of a finer probe because there is less contact with the lips of the wound and less heat damage.

Phaco Tips

The different components of the phaco probeare showninFig.84 left. Pleaseobserve the standard tip (T). The probe is also shown in detail in Figs. 50-A and 50-B in Chapter 7. With the advent of chopping techniques in phacoemulsification, there has been increasing interest in the development of new tips for different uses and purposes. There is a large variety of phaco tips, and each one has its reason for being. Chopping procedures are facilitated by selecting the right tips from a

variety of them as shown in Figs. 51 and 84. Depending on the surgeon’s technique and circumstances of the case, they all can contribute to better control in maneuvering of the nucleus.

In figure 84 (right) and Fig. 51, you may see the most important tips. Fig. 84 A is the Microflow tip, 84 B is the Mackhool-Kelman phaco tip, 84 C is the Aspiration Bypass System (ABS), 84 D the flare head phaco tip, and 84 E is the popular Kelman angled phaco tip. Their specific features are presented in the caption of Fig. 84.

Surgical Principles Behind the

Different Phaco Tips

The different uses for each of these different tips are described in the caption of Fig. 84.

The main variations in phaco tips are related to :1) Angulation. 2) Shape. 3) Size and 4) Thickness. And 5) The existence or not of a protective insulated cover that facilitates cooling so as to minimize the transfer of heat to the surroundingtissues,essentiallythecorneallips of the wound.

The Importance of Angulation and

Beveling

The more beveled is the tip the larger the cutting surface and the larger the area which must be occluded at the tip. Those ranging from 0º to 15º do not cut much but they occlude more easily. They are, therefore, ideal for soft cataracts and for some chopping techniques in which a maximum capacity for occlusion and high vacuum is necessary.

Tips with more angulation and bevel such as 45 degrees have a high capacity to cut the tissues and are very useful for the maneuvers of phacofracture in dense cataracts and in the Divide and Conquer techniques. Nevertheless,these tips offer a higher risk of posteriorcapsulerupturepreciselybecausethey are so sharp and highly cutting.

Importance of Shape and Size

New developments are oriented to microtips and the Mackool system because

they offer more safety and control. The most popular are:

1) Kelman's Turbosonics and

Miniturbosonics

These tips have a curved shape that attains larger contact with tissue surface, internal and external, leading to more cavitation even though the ultrasound energy used may be the same as compared when using the standard tip. Higher cavitation allows destruction of the nucleus beyond the area of touch.

The miniturbosonics is essentially the same style of tip but with lesser diameter.

The main advantages of these tips are: 1) US energy is optimized leading to increased cavitation. 2) Better cutting and slicing of tissues in very hard nuclei.

2) Micro Tips

They all have smaller internal and external diameters as compared with conventional tips. Main Advantages: You can work with smaller incisions and attain greater stability of the anterior chamber because these tips have more resistance to the passing of lens fragments leading to less risk of the Surge phenomenon. They do require, however, more vacuum in order to obtain similar tissue fixation than when using a conventional tips.

These micro tips are the ones indicated for use with the Mackool cassette system that by definition has tubes with narrower inner surfaces and thicker outer surfaces, facilitating the use of higher vacuum and reducing Surge.

In the past three years, there have been dramatic improvements in the technology of phacoemulsification, involving every aspect of phaco systems. These range from the phaco probes and tips all the way down to the foot pedal. Improvements in the generation and controlofultrasonicpower,fluidics,handpieces and tips have been made which are extremely advantageous to the cataract surgeon. We are all indebted to the manufacturers of our instruments and equipments who have invested heavily in financing this research and have attracted the best designers and engineers to carry on these developments.

These systems are able to provide much more reproduceable energy at each power setting regardless of the mass and density of the nuclear material at the phaco tip. Since this load is continually changing, the system must be able to adjust. If not, the efficiency of the equipment is immediately affected.

The main systems available today for phacoemulsification are provided by the major players in industry and have very advanced technology. These systems are the well known Alcon Surgical LEGACY 20,000 equipment (Fig. 85-A), the AMO (Allergan) Sovereign (Fig. 85-B) and the Bausch & Lomb - Storz

Millennium (Fig. 85-C). Allergan's Sovereign isthetopofthelineatAllergan. Theequipment known as Diplomax made available for several years by Allergan is still a useful machine, more portable and of lower price than the Sovereign.

How to Select the Right Equipment for You

In answer to the many questions that we receive from colleagues throughout the world as to which machine or equipment to purchase, we strongly recommend that the first priority should be to select one of these three, but based onthequalityandavailabilityof serviceand technical support that you will be able to obtain in your community. It is useless to have a superb phaco machine if that particular manufacturer provides inadequate technical support in the area where you practice. Each one of these three major systems makes available power modulations and advantages such

Figure 86: Concept of Pulse Mode in Phacoemulsification

Pulse mode provides a great advantage in mobilizing and removing tissue. In pulse mode, the ultrasonic energy can be increased while the pulse rate or application rate of the energy remains constant. One chooses a certain number of pulses per second (P), say 2 pulses per second, which remains fixed during the surgeon's ability to increase the ultrasonic energy level as the foot pedal (F) is depressed in position 3. Note the constant pulse rate (P) as depicted by two pulses shown in front of each tip. Note increasing energy which can be applied, as represented by the enlarging size of the phaco tip and arrow (E), as the foot pedal (F) is depressed. Graph A (Pulse Rate - P/S) shows that pulse rate remains constant (horizontal line) during increased depression of the foot pedal. Graph B (Energy Level) shows that energy application (E) increases in a linear fashion, to a preset maximum, with depression of the foot pedal. Burst Mode, as displayed in the next illustration, is the reverse of Pulse Mode.

as auto pulse phaco, burst mode phaco and occlusion mode phaco which are most important in modern phacoemulsification surgery.

The Pulse and Burst Modes

Differences Between Them

This is one of the most important technological advances in phaco systems, as emphasized by I. Howard Fine, M.D., in the U.S. as well as by Edgardo Carreño, M.D., one of South America’s top phaco surgeons. When you contemplate acquiring a new machine, be certain that it offers these two modalities.

What is the difference between them? In

Pulse Mode we have linear power for a fixed interval of the application of that power (Fig. 86). In Burst Mode, we have fixed power with a variable interval in the application of that power (Fig. 87). Therefore, Pulse is a fixed short interval, Burst is a variable interval.

ClinicalApplicationsofthePulse

Mode

Pulsemodeprovidesagreatadvantagein mobilizing and removing tissue (Fig. 86). In the chopping techniques (Chapter 9), at a fixed pulse rate of 2 pulses per second, the surgeon chops by stabilizing the nucleus with the chop instrument in the golden ring. Fine likes to pull to the side of the phaco needle rather than to the top of the needle so that after the second chop, the initial tissue segment is already lolipopped. (Editor's Note: lolipopped refers to securely engulfing the tip of the phaco into the nucleus, like a lollipop or candy sucker on a stick. The phaco tip is analogous to the stick and the nucleus is the round candy portion - Fig. 88) He does not have to search for the nucleus, or manipulate it: it’s already engaged

on the phaco tip. The vacuum provides substantial control for holding the tissue between applications of phaco power, with almost no potential for chattering. (Editor's Note: chattering refers to when the nucleus bounces against the phaco tip at a high rate of speed without emulsifying it as desired, like when one’s teeth chatter when cold - Fig. 89).

When using the LEGACY 20,000 equipment, for instance, Fine can specifically customize the application of the parameters of phaco power based on differences in the density and type of cataract tissue he is removing. This technological advance is also available in the other outstanding equipment alreadymentioned,particularlyAllergan'sSovereign and Storz (Bausch & Lomb) Millennium.

The power levels used by Fine are very low -- very frequently in the low teens. It is rare

for him to have an effective phaco time greater than 20 seconds and an average phaco power of more than 20 percent. Meanwhile, the vacuum is high, 340 mmHg. He minimizes power and allows high vacuum to do the job.

ClinicalApplicationsoftheBurst

Mode

Its Role in Transition to Chopping

Fine believes the easiest way for surgeonstomakethetransitiontochopping(Chapter 9) is to use the burst mode set for singlebursts with the panel control (Fig. 87). He prefers a burst of 150 ms with vacuum of 400 mmHg. Also, by using Burst mode and a BiModal sub-mode, Fine can use a higher aspiration flow rate to attract the epinuclear ring out of the capsular fornix.

Advances with the Sovereign Phaco System

Just as there are significant advances and technologicalcontributionswiththeprestigious LEGACY 20,000 machine manufactured by AlconSurgical,Allergan hasrecentlybrought intothemarketits Sovereign. Thisisreallythe top of the line for Allergan in this type of surgery. It takes into consideration and actually participates in what all surgeons want which is better and more predictable surgical dynamics for their cataract patients. This equipment has superb fluidics and capacity for programming and provides increasing ease of cataract removal.

The Sovereign utilizes very effectively the micro-processor controls and an on-board computer regulation of all the components,

such as fluidics, ultrasonics, footpedal, and bottle height.

With respect to fluidics, the Sovereign has a digital peristaltic pump that, because of its sophistication, is capable of mimicking every other pump system. Its highly developed responsive fluidics monitoring system, called the Intellesis, monitors the fluidics 50 times per second. There is a sensitive control of what is happening to the vacuum in the anterior chamber. It also has the ability to respond rapidly because the pump can reverse, in addition to move forward, slow, and stop. An inordinately stable anterior chamber can be achieved, with a reduced tendency for vaulting of the capsule or fluctuations in chamber depth (See Chapter 7 - Figs. 62, 63, 65). This new level of control offers optimum safety.

The foot pedal has an on-board computer and is capable of multiple functions (Figs. 52, 53, 55, Chapter 7). The foot pedal can be used with either the toe or heel depending on the surgeon's height. Using the foot pedal, even remote parameters such as bottle height, can be changed.

Another important feature is the ultrasonics which has expanded from a two-crystal to a four-crystal handpiece. This four-crystal handpiece is adaptable to technology from manufacturers other than Allergan. Many machines are not designed to use tips from companiesotherthantheparentcompany. Fine likes to use a Kelman bent tip for certain cases and he can use it with the Sovereign (Figs. 83-B and 84-E.)

The ophthalmologist acquiring a new unit is naturally concerned whether the Sovereign can be programmed and used without extensive study and training in the system. Of course, every surgeon must understand the fundamentals of how phaco machines in general work, as presented in Chapter 7. Accord-

ing to Fine, extensive study is not required because there is a sensor that monitors the delivery of ultrasound energy. It is difficult to keep a system that has a changing mass, shape, anddensityofmaterialatthetipatitsresonance frequency. But this system monitors, through its microprocessors, 50 different functions that are impacting resonance frequency, 500 times a second, and changes and corrects them automatically.

Pulse and Burst Modes on the Sovereign

We have already outlined the great significance and importance of the Pulse and BurstModesapplicablewithAlcon'sLEGACY 20,000 equipment, which is a superb machine (Figs. 86, 87). Fine often combines Pulse and Burst modes also when using the Sovereign. Because the power is intermittent and the

vacuum is constant, one advantage of power modulation is that nuclear material tends to be kept at the tip. Nuclear material seldom chatters (Fig. 89) and almost never shoots into the anterior chamber, where it can threaten the endothelium. Fine feels that the Sovereign represents a new level of finesse and control that leads to safety and ease of operation.

Fine’s Phacoemulsification Parameters includingthePulseandBurstModesforAlcon’s Legacy20,000,Allergan’sSovereignandStorz Millennium,arepresentedinspeciallydesigned Tables in pages 202-203.

Edgardo Carreño’s Adjustable Burst ModeParametersusingAlcon’sLegacy20,000 are presented in this page.

In essence, we have a wonderful new menu of remarkably sophisticated, helpful phaco instrument choices. Each surgeon will need to make his or her own decision, remembering to consider local service and support.