31

Phakonit

Amar Agarwal

Athiya Agarwal, Sunita Agarwal

History

On August 15th 1998 the authors (Amar Agarwal) performed the first 1 mm cataract surgery by a technique called Phakonit.1,2 Since Charles Kelman started phacoemulsif ication, various new modalities have developed which have made this technique more refined. One problem still persists which is the size of the incision. The normal size of the incision is 3.2 mm. With time and more advances in phaco machines and phaco tips this reduced to 2.8 mm and then to 2.6 mm. The authors (Amar Agarwal) performed this technique for the first time in the world on August 15th 1998. It was performed without any anesthesia. No anesthetic drops were instilled in the eye nor was any anesthetic given intracamerally. The first live surgery in the world of Phakonit was performed on August 22nd 1998 at Pune, India by the authors (Amar Agarwal) at the Phako and Refractive surgery conference. This was done in front of 350 ophthalmologists.1,2 In 1999 a live surgery of Phakonit under no anesthesia was telecast live via satellite from India by the authors to Scattle USA to the ASCRS 99 conference.

The problem with this technique was to find an IOL, which would pass through such a small incision. Then on October 2nd 2001 the authors (Amar Agarwal) did the first case of a Phakonit Reliable IOL. This was done in their Chennai (India) hospital. The lens used was a special lens from Thinoptx. This was a Reliable IOL, which was implanted after a Phakonit procedure, and as it was a rolled IOL it was called the Thinoptx Rollable IOL. This lens uses the Fresnel principle and was designed by Wayne Callahan (USA). It is manufactured by the company Thinoptx. The first Rollable IOL was implanted by Jaino Hoyos (Spain). The authors (Am A) modified the lens to a 5 mm optic to make it pass through a smaller incision. The lens goes through a sub 1.5 mm incision.

Principle

The problem in phacoemulsification is that we are not able to go below an incision of 3 mm. The reason is because of the infusion sleeve. The infusion sleeve takes up a lot of space. The titanium tip of the phaco handpiece has a diameter of 0.9 mm. This is surrounded by the infusion sleeve which allows fluid to pass into the eye. It also cools the handpiece tip so that a corneal burn does not occur.3

The authors separated the phaco tip from the infusion sleeve. In other words, the infusion sleeve was taken out. The tip was passed inside the eye and as there was no

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infusion sleeve present the size of the incision was 1.2 mm. In the left hand an irrigating chopper was held which had fluid passing inside the eye. The left hand was in the same position where the chopper is normally held; i.e.; the side port incision. The assistant injects fluid (BSS) continuously at the site of the incision to cool the phaco tip. Dr DP Prakash (India) used a 0.8 mm phaco needle with a 21 gauge irrigating chopper and demonstrated through a digital caliper the incision in this case would be a sub 1 mm incision.

Terminology

The name PHAKONIT has been given because it shows phaco (PHAKO) being done with a needle (N) opening via an incision (I) and with the phako tip (T). It is also because it is phaco with a Needle Incision Technology.

Synonyms

1.Bimanual phaco

2.Micro phaco

3.Micro incision cataract surgery.

Technique of Phakonit for Cataracts

Anesthesia

All the cases done by the authors have been done without any anesthesia. But the technique of Phakonit can be done under any type of anesthesia also. In the cases done by the authors no anesthetic drops were instilled in the eye nor was any intracameral anesthetic injected inside the eye. The authors have analyzed that there is no difference between topical anesthesia cataract surgery and No anesthesia cataract surgery. They have stopped using anesthetic drops totally in all their hospitals.

Incision

In the first step a needle with viscoelastic is taken and pierced in the eye in the area where the side port has to be made. Then a special knife to create an incision is made (Fig. 31.1). The viscoelastic is then injected inside the eye. This will distend the eye so that the clear corneal incision can be made. Now a temporal clear corneal incision is made. The problem here is that the diamond knives are all 2.6 mm or larger. Since our aim is to make only a 1.2 mm opening these diamond knives are not sufficient. So a special blade is used (Fig. 31.2). This creates an opening of 1.2 mm. When this incision is made it should be done in such a fashion that a clear corneal valve is made. The authors have devised a keratome of 1.2 mm which they now use. This keratome creates a good valve.

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This keratome and other instruments for Phakonit are made by Microsurgical Technology (USA) and Gueder (Germany).

FIGURE 31.1 A 26 gauge needle with viscoelastic making an entry in the area where the side port is. This is for entry of the irrigating chopper

FIGURE 31.2 Clear corneal incision made with the keratome (1.2 mm). Note the left hand has a straight rod to stabilize the eye as the case is done without any anesthesia. These instruments are made by Microsurgical Technology (USA) and Gueder (Germany)

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Rhexis

The rhexis is then performed. This is done with a needle (Fig. 31.3). In the left hand a straight rod is held to stabilize the eye. The advantage of this is that the movements of the eye can get controlled as one is working without any anesthesia.

Hydrodissection

Hydrodissection is performed and the fluid wave passing under the nucleus checked. Check for rotation of the nucleus.

FIGURE 31.3 Rhexis started with a needle

Phakonit

After enlarging the side port a 20 gauge irrigating chopper connected to the infusion line of the phaco machine is introduced with foot pedal on position 1. The phaco probe is connected to the aspiration line and the phaco tip without an infusion sleeve is introduced through the incision (Fig. 31.4). Using the phaco tip with moderate ultrasound power, the center of the nucleus is directly embedded starting from the superior edge of rhexis with the phaco probe directed obliquely downwards towards the vitreous. The settings at this stage is 50 percent phaco power, flow rate 24 ml/min and 110 mmHg vacuum. When nearly half of the center of nucleus is embedded, the foot pedal is moved to position 2 as it helps to hold the nucleus due to vacuum rise. To avoid undue pressure on the posterior capsule the nucleus is lifted a bit and with the irrigating chopper in the left hand the nucleus chopped. This is done with a straight downward motion from the inner edge of the rhexis to the center of the nucleus and then to the left in the form of an inverted L shape (Fig. 31.5). Once the crack is created, the nucleus is split till the center. The nucleus is then rotated 180° and cracked again so that the nucleus is completely split into two halves.

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The nucleus is then rotated 90° and embedding done in one-half of the nucleus with the probe directed horizontally (Fig. 31.6). With the previously described technique, 3 pie-shaped quadrants are

FIGURE 31.4 Phakonit irrigating chopper and phako probe without the sleeve inside the eye

FIGURE 31.5 Phakonit started. Note the phako needle in the right hand and an irrigating chopper in the left hand. Phakonit being performed. Note the crack created by karate chopping. The assistant continuously irrigates the phaco probe area from outside to prevent corneal burns

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FIGURE 31.6 Phakonit continued. The nuclear pieces are chopped into smaller pie-shaped fragments

created in one-half of the nucleus. Similarly 3 pie-shaped fragments are created in the other half of the nucleus. With a short burst of energy at pulse mode, each pie-shaped fragment is lifted and brought at the level of iris where it is further emulsified and aspirated sequentially in pulse mode. Thus the whole nucleus is removed (Fig. 31.7). Note in Figure 31.7 no corneal burns are present. Cortical wash-up is to be done with the bimanual irrigation aspiration technique (Figs 31.8 and 31.9). Many doctors like Jorge Alio (Spain), Richard Packard (UK), F Vejanaro (Columbia), Randall Olson (USA) have devised their own instruments for Phakonit.

FIGURE 31.7 Phakonit completed. Note the nucleus has been removed and there are no corneal burns

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Anti-chamber Collapser

One of the real bugbears in Phakonit when we started it was about the problem of destabilization of the anterior chamber during surgery. This was solved to a certain extent by using an 18 gauge irrigating chopper. A development made by us (SA) was to use an anti-chamber collapser4,5 which injects air into the infusion bottle (Fig. 31.10). This pushes in more fluid into the eye through the irrigating chopper and also prevents surge. Thus we were not only able to use a 20 gauge on 21 gauge irrigating chopper but also solve the problem of destabilization of the anterior chamber during surgery. This increases the steady-state pressure of the eye making the anterior chamber deep and well maintained during the entire procedure. It even makes phacoemulsification a relatively safe procedure by reducing surge even at high vacuum levels. Thus this can be used not only in Phakonit but also in Phacoemulsification.

Surge

When an occluded fragment is held by high vacuum and then abruptly aspirated, fluid rushes into the phaco tip to equilibrate the built up vacuum in the aspiration line, causing surge. This leads to shallowing or collapse of the anterior chamber. Different machines employ a variety of methods to combat surge. These include usage of noncomplaint tubing,4 small bore aspiration line tubing,4 microflow tips,4 aspiration bypass systems,4 dual linear foot pedal control4 and incorporation of sophisticated microprocessors4 to sense the anterior chamber pressure fluctuations.

The surgeon dependent variables to counteract surge include good wound construction with minimal leakage5 and selection of appropriate machine parameters depending on the stage of the surgery.5 An anterior chamber maintainer has also been described in literature to prevent surge, but an extra side port makes it an inconvenient procedure. Another method to solve surge is to use more of phacoaspiration and chop the nucleus into smaller pieces.

Technique

A balanced salt solution (BSS) bottle is used (Fig. 31.10). The bottle is kept at a height of about 65 centimeters above the operating field. The automated air pump, which is similar to the pump used in fish tanks to supply oxygen to the fish, is utilized to forcefully pump air into the irrigation bottle at a continuous rate. The air pump is connected to the BSS bottles through an IV set. A millipore air filter is used between the air pump and the infusion bottle so that the air pumped into the bottle is sterile. Sterile air is pumped into the infusion bottle, pressurizing it to force fluid into the anterior chamber, thereby neutralizing surge and maintaining a deep anterior chamber through out the procedure.

Discussion

Surge is defined as the volume of the fluid forced out of the eye into the aspiration line at the instant of occlusion break. When the phacoemulsification handpiece tip is occluded, flow is interrupted and vacuum builds up to its preset values. Additionally the aspiration

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tubing may collapse in the presence of high vacuum levels. Emulsification of the occluding fragment clears the block and the fluid rushes into the aspiration line to neutralize the pressure difference created between the positive pressure in the anterior chamber and the negative pressure in the aspiration tubing. In addition, if the aspiration line tubing is not reinforced to prevent collapse (tubing compliance), the tubing, constricted during occlusion, then expands on occlusion break. These factors cause a rush of fluid from the anterior chamber into the phaco probe. The fluid in the anterior chamber is not replaced rapidly enough to prevent shallowing of the anterior chamber.

The maintenance of intraocular pressure (steady-state IOP) during the entire procedure depends on the equilibrium between the fluid inflow and outflow. In most phacoemulsification machines, fluid inflow is provided by gravitational flow of the fluid from the balanced salt solution (BSS) bottle through the tubing to the anterior chamber. This is determined by the bottle height relative to the patient’s eye, the diameter of the tubing and most importantly by the outflow of fluid from the eye through the aspiration tube and leakage from the wounds.

The inflow volume can be increased by either increasing the bottle height or by enlarging the diameter of the inflow tube. The intraocular pressure increases by 10 mmHg for every 15 centimeters increase in bottle height above the eye.5 High steadystate IOPs increase phaco safety by raising the mean IOP level up and away from zero, i.e. by delaying surge related anterior chamber collapse. Air pump increases the amount of fluid inflow thus making the steady-state IOP high. This deepens the anterior chamber, increasing the surgical space available for maneuvering and thus prevents complications like posterior capsular tears and corneal endothelial damage. The phenomenon of surge is neutralized by rapid inflow of fluid at the time of occlusion break. The recovery to steady-state IOP is so prompt that no surge occurs and this enables the surgeon to remain in foot position 3 through the occlusion break. High vacuum phacoemulsification can be safely performed in hard brown cataracts using an air pump. Phacoemulsification under topical or no anesthesia6 can be safely done neutralizing the positive vitreous pressure occurring due to squeezing of the eyelids.

Thinoptx Reliable IOL

Thinoptx the company that manufactures these lenses has patented technology that allows the manufacture of lenses with plus or minus 30 dioptres of correction on the thickness of 100 microns. The Thinoptx technology developed by Wayne Callahan, Scott Callahan and Joe Callahan is not limited to material choice, but is achieved instead of an evolutionary optic and unprecedented nano-scale manufacturing process. The lens is made from off-the-shelf hydrophilic material, which is similar to several IOL materials already on the market. The key to the Thinoptx lens is the optic design and nanoprecision manufacturing. The basic advantage of this lens is that they are Ultra-Thin lenses. Thinoptx has made a special lens for Phakonit which has a 5 mm optic.

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FIGURE 31.13 The reliable IOL in the capsular bag

The lens is then inserted through the incision carefully (Fig. 31.12). One can then move the lens into the capsular bag (Fig. 31.13). The natural warmth of the eye causes the lens to open gradually. Viscoelastic is then removed with the Bimanual irrigation aspiration probes (Fig. 31.14). The tips of the footplates are extremely thin which allow the lens to be positioned with the footplates rolled to fit the eye.

FIGURE 31.14 Viscoelastic removed using bimanual irrigation aspiration probes

Roller

Thinoptx have devised a special injector to implant the Reliable IOL after Phakonit. The advantage of this roller is that it not only rolls the lens but also inserts the lens inside the eye.

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Topography

We also perfomed topography with the orbscan to compare cases of phakonit and phaco and we found that the astigmatism in phakonit cases is much less compared to phaco (Figs 31.15 to 31.18). Stabilization of refraction is also faster with Phakonit compared to phaco surgery.

Laser Phakonit

Laser Phakonit uses laser energy (coupled with ultrasound energy in hard nuclei) to remove the nucleus. This technique was started first time in the world by the authors (Sunita Agarwal). The laser machine used is the Paradigm Laser Photon. In these cases, two ports are used. One port has fluid (BSS) flowing through an irrigating chopper of 20 gauge and in the other hand is the phaco probe without a sleeve. In the center of the phaco probe is passed the laser probe. The diameter of the phaco probe is 900 microns. The laser probe reduces the orifice opening to 550 microns. Thus the nucleus can be removed through a very small opening.

FIGURE 31.15 Phako foldable and phakonit thinoptx IOL. The figure on the left shows a case of phako with a foldable IOL and the figure on the right shows phakonit with a thinoptx reliable IOL

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FIGURE 31.16 Phako foldable IOL orbscan results. The figure on the left is the preoperative orbscan. The figure on the right is the one day postoperative orbscan. Note the difference between the two orbscan pictures. This is the site where the clear corneal temporal incision was made

Three-Port Phakonit

Another technique by which one can perform Phakonit is to use an anterior chamber maintainer. The authors started this technique. They call it three-port phakonit. Just as a three port vitrectomy, here also we have three ports, hence the name- Three-Port Phakonit.

There are pros and cons in every technique. The problem in three-port phakectomy is that it is too

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figure on the left is the preoperative orbscan. The figure on the right is the one day postoperative orbscan. Note the similarity between the two orbscan pictures. This shows no astigmatism created even on one day postoperative. Do note the astigmatism preoperative is 0.8 d and postoperative on day one is 0.7 d

cumbersome. Surgeons prefer to have two ports only. Some surgeons prefer three ports as an anterior chamber maintainer is present in the eye and thus the anterior chamber is always formed. At present it is easier to perform Phakonit using a 20 gauge irrigating chopper with the anti-chamber collapser.

AC Stability in Phakonit

One of the real bugbears in Phakonit when we started it was about the problem of destabilization of the anterior chamber during surgery.1–5 This was solved to a certain extent by using an 18 gauge irrigating chopper. Another solution would be to raise the bottle to the roof which is not very practical. The main problem in Phakonit was that the amount of fluid entering the eye through the irrigating chopper was not equal to the amount of fluid exiting the eye through the sleeveless phaco needle. With better methods as discussed below on AC stability one can use a 21 gauge irrigating chopper.

Solution

Different surgeons have tried different methods to solve this problem of anterior chamber stability. The various methods are-

1.Air pump or Anti-chamber collapser

2.Anterior Vented Gas Forced Infusion System (VGFI) of the Accurus Surgical System

3.STAAR Surgical’s disposable Cruise Control device

4.Well designed irrigating choppers from Duet (Microsurgical Technology).

The anterior vented gas forced infusion system (AVGFI) of the Accurus Surgical System in the performance of phakonit

This was started by Arturo Pérez-Arteaga from Mexico. The AVGFI is a system incorporated in the Accurus machine that creates a positive infusion pressure inside the eye; it was designed by the Alcon engineers to control the intraocular pressure (IOP) during the anterior and posterior segment surgery. It consist of an air pump and a regulator who are inside the machine; then 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

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panel; it also can be controlled via the remote. Also the footswitch can be preset with the minimal and maximum of desired fluid inside the eye and go directly to this value with the simple touch of the footswitch. Arturo Pérez-Arteaga recommends to preset the infusion pump at 100 to 110 cm H2O; it is enough strong irrigation force to perform a microincision phaco. This parameter is preset in the panel and also as the minimal irrigation force in the footswitch; then he recommends to preset the maximum irrigation force at 130 to 140 cm H2O in the foot pedal, so if a surge exist during the procedure the surgeon can increase the irrigation force by the simple touch of the footswitch to the right. With the AVGFI the surgeon has the capability to increase even more these values.

Cruise Control

The Cruise Control is a disposable, flow-restricting (0.3-mm internal diameter) device that is placed in between the phaco handpiece and the aspiration tubing of any phaco machine. The goal is very similar to that of the flare tip (Alcon): combining a standard phaco tip opening with a narrower shaft to provide more grip with less surge. This has been popularized by David Chang (USA) for phakonit surgery. STAAR Surgical introduced this disposable Cruise Control device, which can be used with any phaco machine.

FIGURE 31.19 Phakonit knives. The one on the left is the Agarwal sapphire phakonit knife made by Huco (Switzerland). The one on the right is the one made by Microsurgical Technology

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FIGURE 31.20 Duet system. These are the handles of the Duet system (Microsurgical Technology). The irrigating choppers and bimanual irrigation aspiration sets can be interchanged with the handles

FIGURE 31.21 Two designs of irrigating choppers. The one on the left has a larger opening for fluid so that AC stability is more. This has been designed by Larry Laks (Microsurgical Technology). The one on the right has two openings on the sides (Gueder— Germany)

Duet System

Larry Laks (USA) created the Duet system (Micro-surgical Technology-MST). The advantage of this was a whole bimanual phaco set for Phakonit. The Duet system has

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phakonit knives also (Fig. 31.19) and also handles on which various irrigating choppers can fit (Fig. 31.20). The Microsurgical Technologies (MST) 20 gauge Duet irrigating choppers provide the best inflow of comparable

FIGURE 31.22 Clear corneal incision made with the microsurgical technology knife

FIGURE 31.23 Phakonit being done with the Agarwal sharp irrigating chopper from Microsurgical Technology

devices. The MST shaft design gives an impressive inflow rate of 40 cc/min at 30 in of bottle height and is available with an assortment of interchangeable chopper tips. This whole design was created by Larry Laks. The idea was to have the opening in the irrigating choppers larger (Fig. 31.21). The clear corneal incision can be created with the

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MST knife (Fig. 31.22) and then Phakonit started using the Agarwal sharp MST irrigating chopper (Fig. 31.23).

FIGURE 31.24 Bimanual irrigation aspiration started using the Duet system (MST)

FIGURE 31.25 Bimanual irrigation aspiration completed

TABLE 31.1 The differences between phako and phakonit

Once Phakonit is completed the Bimanual Irrigation aspiration set from the Duet system is used (Fig. 31.24) and the cortical aspiration completed (Fig. 31.25).

Summary

There are various problems, which are encountered, in any new technique and so also with Phakonit. With time these will have to be solved. The differences between phako and phakonit are shown in Table 31.1. The important point is that today we have broken the 1 mm barrier for cataract removals. This can be done easily by separating the phaco needle from the infusion sleeve. As the saying goes—

“We have miles to go before we can sleep”.

References

1.Agarwal S, Agarwal A, Sachdev MS et al: Phacoemulsification, Laser Cataract Surgery and Foldable IOLs (2nd ed). Jaypee Brothers: Delhi, 2000.

2.Boyd BF, Agarwal S, Agarwal A et al: Lasik and Beyond Lasik; Highlights of Ophthalmology; 2000, Panama.

3.Ronge LJ: Clinical Update; Five Ways to avoid Phaco Burns; February 1999.

4.Fishkind WJ: The Phaco Machine: How and why it acts and reacts? In: Agarwal’s Four volume Textbook of Ophthalmology. Jaypee Brothers: New Delhi, 2000.

5.Seibel SB: The fluidics and physics of phaco. In: Agarwal’s et al: Phacoemulsification, Laser Cataract Surgery and Foldable IOLs (2nd ed). Jaypee Brothers: New Delhi; 45–54, 2000.

6.Agarwal et al: No anesthesia cataract surgery with karate chop. In: Agarwal’s

Phacoemulsification, Laser Cataract Surgery and Foldable IOLs (2nd ed). Jaypee Brothers: New Delhi, 217–26, 2000.