1.3 0.7 mm Microincision Cataract Surgery

Irrigation and aspiration of cortex: This is perhaps an area where bimanual MICS is truly advantageous. Twenty gauge bimanual irrigating and aspirating instruments are each inserted into the eye. The aspirating probe is used to remove the cortex and if there is difficulty removing the subincisional cortex, the probes may be switched to reach the subincisional cortex.

IOL insertion: There are two methods commonly used for insertion of the IOL: either a 2.8 mm incision may be created between the two stab incisions or one of the stab incisions may be enlarged. Following the injection of the IOL into the capsular bag, residual viscoelastic is removed and all wounds are stromally hydrated. However, more recently, newer generation IOLs have become available that can easily go through a sub-2.0 mm incision.

1.2.3 Summary

Biaxial microincisional cataract surgery has its advantages. Irrigation through the side-port can help direct pieces of nuclear material towards the phaco tip. It minimizes the opposing forces of coaxial irrigation at pushing the nuclear material away. Slightly lower infusion pressure and the split of irrigation with the ability to control the fluid stream direction away from areas of zonular instability make it more beneficial in challenging cases. Also, if needed, nuclear material can be approached from both incision sites. With the availability of microincision IOLs, the procedure is more tightly controlled, the eye is more stable and less astigmatism is induced. This is the procedure of today and the future.

Take-Home Pearls

ßMicrosurgery for phacoemulsification represents the next evolution in techniques for cata-

ract surgery.

ßDo not change your technique or change too many parameters at one time.

ßStart slowly and pick the right case and patient.

ßBimanual MICS is safe and effective.

1.30.7 mm Microincision Cataract Surgery

Jorge L. Alió, Amar Agarwal, and

Pawel Klonowski

Core Messages

ßTo perform 0.7mm MICS (microincision cataract surgery) you need new 21 gauge instruments

ßTo achieve stable fluidics in the anterior chamber it is necessary to use pressurized infusion

ß0.7 mm MICS is the new limit of cataract surgery in terms of incision size

ß0.7mm MICS is possible in all cataract cases with today’s improvements in phaco technology

1.3.1 Sub 1 mm MICS: Why?

The natural trend of modern surgery is to minimize the physical aspects of intervention in the human body. During the last 40 years, cataract surgery has made the huge step from the 10–12 mm incision to the 0.7 mm incision. Not only the incision, but even the energy delivered, the surgical trauma and the time of the surgery have decreased. Nowadays, with millions of cataract surgeries performed annually around the world, the technique and outcome of surgery have become more efficient and predictable. Only minimal invasive surgery can improve the refractive result [1–3]. Many papers have confirmed the dependence between incision size and postoperative astigmatism, or corneal aberrations [4, 5]. This makes the surgery more efficient and faster. Reduction of incision size seems to be the trend in the normal evolution of surgery, and it will continue to be a challenge even in the future.

A. Agarwal ( )

Eye Research Centre & Dr. Agarwal’s Group of Eye Hospitals, 19 Cathedral Road, Chennai 600 086, India

email: dragarwal@vsnl.com

On 15 August 1998, Amar Agarwal performed 1 mm cataract surgery by a technique he called Phaconit (phaco being done with a needle incision technology) [6–11]. One of the authors, Jorge Alió, coined the term MICS – microincision cataract surgery – for all sub-2 mm surgeries [12]. On 21 May 2005, for the first time, a 0.7 mm phaco needle tip with a 0.7 mm irrigating chopper was used by one of the authors to remove cataracts through the smallest incision possible so far (Microphaconit – 0.7 mm MICS).

The MICS concept was put into practice following the MICS principles:

1.New MICS instruments

2.Increased use of vacuum and improved fluidics

3.Closed and stable anterior chamber

4.Less use of power settings, reduced use of ultrasound energy

5.Adequate MICS IOL

These conditions allow applying MICS surgery and making surgery much more:

1.Predictable

a.Diminishing surgically induced astigmatism

2.Controllable

a.Stable anterior chamber

b.Stable position of the posterior capsule

c.Higher effectiveness of the phaco fragmentation and aspiration

3.Uncomplicated

a.Bimanual access

b.Small tools maneuvers

c.Stable conditions

The appropriate combination of these conditions and the proper application of the instruments and machine setting make sub-1 mm surgery possible. Now MICS and 0.7 mm MICS are the standard procedures performed by authors. The right use of the tools and the adequate setup of the machine fluidics help to operate all grades of cataracts, including complicated cataracts. The surgery is more controllable if properly performed.

By choosing the right instruments and fluidics, it is possible to get all types of cataracts, even complicated ones, through sub-1 mm incision.

The main purpose of this chapter is to describe the approaches and techniques used by the authors to make a transition towards 0.7 mm MICS.

1.3.2Potential Drawbacks of a Sub-1 m Incision

The transition towards performing 0.7mm MICS requires more attention to the incision and fluidics. The inadequate settings of machine parameters (US power, vacuum and pressured infusion) may result in incision burn, corneal trauma and anterior chamber instability.

The principles of application for 0.7 mm instrumentation are the same as in MICS. The most important change is the diameter of instruments and the use of high vacuum and pressured fluidics. The instruments have to be compatible with these parameters.

New micro MICS instrumentation should allow better fluidics and should

–Fit through minimal new incisions

–Be ergonomic

–Allow multiple functions

–Be safe

–Be easy to use

The main problem in 0.7 mm MICS is the destabilization of the anterior chamber during surgery. Smaller dimension of the instruments needs to be achieved by increasing the potential of the fluidics. Now with a 22 gauge (0.7 mm) irrigating chopper it is essential that pressured infusion be used in the surgery. Some of the new phaco machines are equipped with internal air pumps: Accurus (Alcon Laboratories) and the Millennium (Bausch & Lomb). This technique is called internal gas forced infusion (IFI). The filtered air is pressed into the BSS bottle. The anterior chamber is filled with the salt solution under stable conditions. This type of GFI is well verified in MICS surgery. The surgeon has perfect control of this parameter at the machine platform during different stages of the surgery. These machines maintain the infusion at a stable level.

The second option is to connect the external air pump to the infusion bottle. This option is inexpensive but gives less control of the infusion (Fig. 1.11).

The advantages of pressured infusion are listed below:

1.The surgeon can control all the parameters (forced infusion rate, ultrasonic power modulations and vacuum settings) in the same panel of the surgical system.

2.The forced infusion rate can be actively and digitally controlled during the surgery, adjusting the parameters to the conditions and/or the surgical steps of each individual case and balancing the inflow and outflow by internal intraocular pressure (IOP) control in modern cataract machines.

3.Bottle height becomes irrelevant as a key factor in surgical control with the consequent advantages for OR design.

Other advantages of ressured infusion are:

1.Continuous and active infusion

2.Stable amount of fluid delivered into the eye

3.Maintaining stability of the anterior chamber

4.Continuous rapid cooling of the phaco tip

5.Posterior capsule is situated in the secure position

6.Gives opportunity for safe maneuverings in the anterior chamber

One of the authors (Amar Agarwal) has mainly worked with anterior vented gas forced infusion system (AVGFI) of the Accurus surgical machine that helps in the performance of MICS/Phakonit [13–15].

This was started by Dr. Arturo Pérez-Arteaga from Mexico. The AVGFI is a system incorporated into the Accurus machine that creates a positive infusion pressure inside the eye. It consists of an air pump and a regulator which are inside the machine; the air is pushed inside the bottle of intraocular solution, and so the fluid is actively pushed inside the eye without raising or lowering the bottle. The control of the air pump is digitally integrated in the Accurus panel.

Table 1.1 presents the outflow of fluid from various types of irrigating choppers when the Accurus infusion pump is set at 100 mmHg or when the external pump is connected (Table 1.1) The external air pump has two modes of action. Mode high is equal to using the Accurus machine at about 100 mmHg pressure. Mode low of the air pump is equal to using the Accurus machine at 50 mmHg pressure. The use of the millipore filter is mandatory to protect against and prevent any infection. We measured the amount of fluid coming out of the various irrigating choppers with and without an air pump. We measured the values using the simple external air pump (external gas forced infusion) and the Accurus machine with IFI.