Fig. 5.25 Irrigating cannula with Forced Infusion active inside the anterior chamber. The bottle height is less important

feel confident and will see the advantages of direct vacuum technology over the peristaltic pumps. MICS works well with high vacuum levels, in particular, if you have the “no-surge insurance” that allows the forced infusion.

4.Amphibian possibilities (anterior segment only, posterior segment only, or combined procedures)

This is another important advantage of the Accurus system; it allows you to perform combined procedures (phacoemulsification and posterior vitrectomy) at the same surgical time (Fig. 5.22), with the same machine, decreasing this way, the risk of a second procedure for some patients (e.g., diabetic group), but also allowing economical benefits. It has a powerful vitrectomy system, which means a tremendous advantage in case of vitreous loss and the need of anterior vitrectomy; it can be done in a biaxial approach and with high cut parameters without the need to change machines (Fig. 5.26). This is not possible in other systems used for phacoemulsification only. So this system increases the possibilities of the vitreous management (planned or unplanned), allowing this way to an important increase in the safety of the procedure and for the patient.

5. Economical features

There are many points of view to approach the economical reasons for performing MICS with an Accurus, far away from the medical reasons:

•A combined procedure for anterior and posterior segment at the same surgical time decreases the surgical cost.

•The anterior and posterior segment surgeons can also work in different days, making the machine useful and working every day.

•If desired, the cassette system of this machine can be easily disassembled, allowing the surgeon to resterilize it for each and every case in a safe way, thereby decreasing the cost of a cassette per procedure mandatory in other phaco systems.

5.3.1.3Surgical Parameters for MICS with Accurus

1. Irrigation

Because the surgeon is working with forced infusion, it has to be remembered that the bottle height is now not important. The bottle should be placed at the level of the machine, at the site described by the manufacturer (Fig. 5.25); the bottle height will not change while the forced infusion is at work. Nevertheless, some surgeons like to work MICS with the Accurus surgical system without the use of forced infusion utilizing only passive infusion (gravity force) to irrigate inside the eye; but we believe that this particular feature of this system must be in use in every case of MICS since it increases the control.

The initial parameter will depend upon the diameter of the irrigation device; the same amount of forced infusion (e.g., 110 cmH2O) will lead to more infusion rate (ml/min) in a wider irrigation device (e.g., 19 G irrigating chopper) when compared with a

Fig. 5.26 Change of parameters and instrumentation with the same machine for many purposes

small diameter irrigation device (e.g., 22 G irrigating chopper) (Fig. 5.16). So we strongly recommend to determine the forced infusion needed to obtain a desired infusion rate with the diameter of instrumentation available for the surgeon. An ideal parameter of reference is 45 ml/min (Fig. 5.24); so before starting to operate, connect your AVGFI, preset the forced infusion at the determined measure (e.g., 100 cmH2O), collocate your irrigating chopper at the end of the line, and switch-on the irrigation, measuring in a graduated glass the amount of fluid outgoing within 1 min (or 30 s multiplied by two). If you obtain less than 45 ml in a minute, increase the pressure (e.g., 110 cmH2O) and measure again; if you obtain more than 45 ml, decrease the pressure (e.g., 90 cmH2O) and measure again. Establish and register this parameter for each irrigating device (chopper or cannula) that you have, even if they are of the same measure, because sometimes the lumen size can vary according to different models and manufacturers. Once you have the amount of pressures needed for each of your irrigating devices, you are ready to start.

Even so, we can recommend some initial parameters according to the size of the irrigation devices: 90–100 cmH2O for 19 G, 100–110 cmH2O for 20 G, 110–120 cmH2O for 21 G, and 120–140 cmH2O for 22 G. Remember that when you experience surge you can increase the amount of forced infusion during surgery, and so you can preset two parameters at the panel of the machine and then switch between them with the foot-pedal (Fig. 5.21).

When you enter the anterior chamber and the incisions have been properly made and even the irrigation is switched-on, an equilibrium of pressures will be established between the air cushion inside the bottle, and the intraocular pressure (IOP); so you will not obtain any irrigation or any leakage (Fig. 5.27); it means that you have the right pressure and you can start with your sleeveless phacoemulsification; the fluid incoming will compensate just the fluid outgoing, and during the periods of no-aspiration, there will be no fluid incoming the eye (just like how the fluids work in a posterior vitrectomy procedure). An advantage of MICS, in particular with diameters less than 1 mm, is that the amount of total fluid utilized is by far less in comparison to the co-axial procedures.

2. Aspiration

Because it works with venturi system, it has no parameters regarding a peristaltic pump (aspiration rate); so

Fig. 5.27 Biaxial Anterior Vitrectomy. Balance of pressures between the irrigating force and the anterior chamber

the only one parameter to control vacuum is the amount of suction expressed in mmHg. If you do not feel confident enough to work with high vacuum levels, a good value for starting can be something between 150 and 200 mmHg. As you start to feel confident, you can increase the parameters to higher values like 250 and 300 mmHg.

The advantage of working with high vacuum levels is the decrease in the ultrasonic time and power, because the vacuum force acts as the main force to aspirate the nuclear pieces; this concept increases in value, in particular, when using Kelman tips that helps to produce a mechanical disruption of the pieces and of course if prechop techniques are applied before starting ultrasonic force.

3. Phacoemulsification

If a Stop & Chop technique is going to be performed and so sculpting the nucleus is under the surgical program, 25–35% of lineal phaco power is a good way to start in a continuous mode, followed by intermittent phaco (pulse or burst), just like the surgeon is accustomed to operate with any other phaco machine. If prechop techniques are in the field, no continuous phaco will be needed, and only the intermittent modes will be in use.

Even though many detractors of this technique have mentioned about the increase in the incidence of corneal thermal burns (because of the sleeveless phaco needle), it has been demonstrated in many publications of editors and contributors to this book that it is not true; the sleeveless surgery is not the cause of the

corneal damage; deficient incision architecture, increase in phaco time and power, persistence of viscoelastic in the chamber and surge have been demonstrated as the main causes of corneal damage at the incision site; so the learning surgeon must not be frightened to start.

If we follow the current definition of phacoemulsification for cataract surgery (mechanical nuclear fragmentation followed by phacoaspiration assisted by intermittent and low ultrasonic force), a maximum of 40% of preset phaco power should be the starting parameter of choice.

IOP is always present. Good parameters to start may be 60–80 cmH2O of forced infusion (remember always to decrease the infusion when your posterior capsule is broken), 150–200 mmHg of vacuum and 800 cuts per minute; with some particular posterior vitrectors, in combination with the software inside the phaco machine, you can perform more than 1,500 cuts per minute. The high speed biaxial vitrectomy is an advantage that you can only obtain with a hybrid machine; so do not let it go when needed.

4. Biaxial irrigation/aspiration

You can have preprogrammed parameters for the time to switch to I/A mode. Because the aspirating cannula has a smaller internal diameter than the phaco tip, less amount of irrigation and more amount of aspiration are needed; remember to test the rate as an initial point of departure. For biaxial I/A sets going from 19 to 22 G, ideal starting parameters are 80–100 cmH2O of forced infusion and 350–400 mmHg of vacuum; this can allow you to have a positive IOP again, no surge, enough aspirating force and fluid incoming just compensating the fluid outgoing. If the technique (in particular, suitable incisions construction) is properly done, the entire I/A can be done with no more than 20–25 ml of saline intraocular solution.

5. Biaxial anterior vitrectomy

You can also preprogram your parameters for an eventual vitreous loss. You should always keep in mind that you are operating under a biaxial approach and have a high performance machine for posterior segment surgery (unfortunately not possible when operating with an exclusive anterior segment machine); so do not try to perform the anterior vitrectomy in a coaxial approach because you will loose the entire sense of the surgery; do it in a biaxial mode (Figs. 5.25 and 5.27).

Insert the instruments (irrigation-vitrector) as you like: cornea–cornea, sclera–cornea, cornea–sclera, or sclera–sclera, but take advantage of the biaxial approach. You are working in a closed environment, the forced infusion pushes the vitreous behind the iris plane, you can have access to 360° and the positive

5.3.1.4 Final Considerations

As you have noticed after reading this chapter, the Accurus surgical system has some specific features that can increase the safety of your MICS procedure, and can also allow the converting surgeons to transit through a smooth learning curve:

1.Digitally controlled air pump for infusion system.

2.Possibility to preprogram two different infusion pressures for different steps of the surgery, controlled in the foot-pedal by the surgeon (only one machine with this feature in the market).

3.No need to depend upon the force of gravity to create infusion, in particular, in ultra-small incision surgery.

4.Safe mode for resterilization of the cassette because of an easy disassembly.

5.Phacoemulsification features as in many other phacoemulsification machines worldwide.

6.High vacuum system.

7.Digitally controlled direct venturi system to create vacuum.

8.Direct and instantaneous reflux created with the same system, not depending upon a peristaltic pump.

9.Digitally controlled, high speed, biaxial anterior vitrectomy for cases of vitreous loss.

10.Possibility to perform combined procedures (cataract surgery plus posterior virectomy).

11.Posterior vitrectomy complete system if needed in the same surgical time (e.g., nucleus or IOL drop into the vitreous cavity).

Take Home Pearls

ßThe use of fluidics control utilized for posterior vitrectomy to the cataract surgery is an

important advancement in modern-day cataract surgery, particularly in MICS.

ßOnly the machines that have posterior segment surgery and that can perform phacoemulsifica-

tion (hybrid systems), are able to make full use of the advantages of the internal forced infusion.

ßMICS becomes easier and safer for the surgeon when the fluid inflow into the eye is larger than

the fluid outflow, even when using high vacuum, in the Accurus machine.

ßRemember to be sure to preprogram your settings according the diameter of your irrigating devices,

phaco needles and aspirating cannulas, before starting to operate, in order to avoid unwanted surgical surprises. You must individualize the parameters according the instrumentation that you use in MICS.

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