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Laser Phaco Cataract Surgery

Sunita Agarwal

J Agarwal, T Agarwal

Introduction

From the time of its inception in 1949 with Meyer Schwickerath in Germany the concept of lasers has caught the imagination of child and adult alike, scientist and the public in general. Science fiction movies are made with the concept of the laser as the ultimate weapon against all evil. Little wonder then as eye surgeons we are always trying to better the techniques of cataract removal over the years, thus today with lasers we find ourselves equipped with one more wonderful tool in the armamentarium of the operating room.

We are in the midst of a paradigm shift in cataract surgery today. We must either become a part of the shift or we will be blind-sided by it. Today, one of the latest developments in ophthalmology is the laser cataract surgical system. The laser cataract surgery system would entail less trauma and better rehabilitation of the patient.

History

Cataract the bane of old age has been known as a disease process to human civilization for many years. Earliest records of its treatment were carried out by Sushruta 500 BC the famous Indian surgeon who practiced a form of medicine called Dhanvantri. He used a needle with no anesthesia, through a bloodless route entered the eye through the cornea and dislodged the cataract. The needle would stick into the cataract like a lollipop and small movement of the cataract to and fro would break its zonular attachments. Then the cataract would be made to fall into the deep vitreous. This saved many a eye in that era and times, however many fell prey to the adversities of the posterior segment. Yet today we have come a full circle by bringing in the concept of no anesthesia, bloodless, painless, laser phaconit (needle surgery) cataract surgery.

This idea of couching traveled the silk route into the Arab world and reached the far corners of Europe. However somewhere along the 11th century an Arabian scientist Ammar came up with the methodology of removing the cataract enbloc out of the eye. Thus, started the road of intracapsular cataract and extracapsular cataract extraction. For many years the cataract would need to be rippend before the surgeon would go to remove it.

Somewhere along the last two centuries sutures came into being and cataract surgery became more and more safe where the eye and life were concerned. However it was the

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remarkable discovery by Sir Harold Ridley of PMMA pieces of plastic broken from the windshield of planes, lying insert in the eyes of pilots of the Royal Air Force during the Second World War. This led him to believe and rightly so that pieces of plastic could be permanently placed in the eye to replace the lost condensing power of the eye. Thus started the saga of intraocular lens in 1949.

However it was the conception of the ultrasound power by Charles Kelman in 1970 that made it really possible to make cataract surgery as atraumatic experience as we see it today. It was also this ideology, which made industry look around and give us the foldable intraocular lens.

With the last two decades research into the idea of lasers removing cataracts grew stronger and stronger. We had some surgeons carrying out Nd: YAG laser capsulotomy preoperatively over a slit lamp delivery and then taking the patient immediately to the operation theater to remove the cataract and replace with an intraocular lens.

Around the latter part of the 80s a few patent applications were accepted for laser cataract surgery per se. Here Dr. Eichenbaum created history by teaming up with Paradigm Laser Photon and bringing out the first commercially available laser cataract surgery system.

FIGURE 36.1 Laser photon machine from paradigm (USA)

It was the author’s (SA) good fortune to acquire such a machine way back in 1995 and with continuous efforts from the parent principal company and the experience handed over through patients, evolution of this methodology for cataract surgery has increased ever more.

Laser Cataract Surgery

At the time when I first got the laser photon machine from Paradigm (Fig. 36.1) all I could see was it was a powerful machine. The laser fiber optic actually could burn a hole in steel, thus I wondered if such a machine can make a hole in steel a cataract tissue would be child’s play for it.

However, there were many barriers to this thinking and soon I realized that evolution of a better system was needed. The fluidics which make such an important part of cataract surgery today was in its infantile phase. We were actually holding vacuum levels at less than 100 mm of Hg and this was not fast enough to remove cataract tissue.

The major problem that all high-energy source have is, even though they may disintegrate the tissue instantaneously they also have the repulsion to push away the piece from the aspirating porthole. Combating this element with another physical capacity of the laser being heat was another ball game altogether.

Nd: YAG laser was carried to the tip of the probe through a fiberoptic and instilled inside the suction arena with a sleeve outside bringing in the fluids. The laser has the capacity to ablate solid tissue on coming into contact, to about 20 microns tissue space. However a small part of the tissue around this area of action would get caseated due to the high protein content, slow aspiration rate and high temperatures. This caseating mass would then plug the aspirating porthole and the surgery would have to wait till the mass was deluged.

This kind of method continued for sometime until I realized this was not going to be effective enough. Another aspect of laser cataract surgery is due to the probe fashioned in the manner of a spoon. With the aspiration in the deep part of the spoon, occlusion was next to impossible.

We had learned till then the cataract was to be divided and conquered, if occlusion was not possible then divide and conquer was not possible. So started our road of incorporating the laser with the ultrasound. The patents for this probe were filed that same year, because we had understood this was the wonderful link between ultrasound and lasers.

This became the method of choice for tackling hard and soft cataracts alike. Today we are slowly moving away and away from ultrasound because we understand the endothelial damage in an already compromised cornea. Thus the increased interest in the laser that can remove the cataract with the ease of an irrigation aspiration handpiece yet the power of the ultrasound vibrating needle.

We have much better fluidic control, our aspiration rates can touch 350 to 400 mm of Hg, and this allows the cataract to get sucked in before it has time to caseate on the tip. The laser is much better centered in the probe allowing all the laser energy to be targeted along the cataractous tissue.

We have developed newer technologies for cataract removal without having to subject the cataract into a divide and conquer routine we are able to remove the cataract with a carouselling technique

“Like each temple to its own deity and each monastery to its own monk so is each technique to its own master.” From the words of Jackie Chan, this relates so to in our advanced laser phaco techniques, where each surgeon has their own techniques.

Pioneers

For decades now we have known benefits of the ultrasound energy. Incorporated with Dr Kelmans path breaking in roads of using this energy for the removal of cataracts has indeed reduced rehabilitation of the cataract patient.1–7

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Four top ophthalmologists have been working independently on the system of developing a laser to help in cataract removal. The first has been Dr Daniel Eichenbaum from USA. It has been basically due to Dr Daniel Eichenbaum and Paradigm that the laser cataract removal system could be started. They have developed a machine called the Laser Photon. This laser photon uses the Yag laser for cataract removal.

The second ophthalmologist Dr Jack Dodick introduced the use of the Yag: YLF laser for surgical cataract removal. A laser beam is a fiber-optically directed toward a titanium mirror target. The reflection produces waves of optical breakdown power, resulting in photoablation of the surface down to any depth desired. Succeeding generations of instrumentation for this technique have been modified and refined. The probes are getting thinner and thinner compared to a phacoemulsification tip.

The third ophthalmologist is Dr Michael Colvard. The Erbium laser is being used by Michael Colvard to ablate ocular tissue and its advantage is that it has maximal absorption in water. When properly directed and mirrored, as in Dodick’s approach, the laser beam is kept away from the posterior pole and the retina. Safety seems to be built into reflected laser ablation, allowing ablation without thermal injury. In Colvard’s technique, the laser beam is placed directly in contact with the nucleus of the cataract for nonpercusssive cutting. By directing the beam much as one would use an eraser to wipe over the surface, the tip of the beam is directed over the ablation zone, causing optical breakdown just at the beam’s tip. The nuclear material is then removed with irrigation and an IOL is implanted.

FIGURE 36.2 Sunita Agarwal’s laser phaco probe

The fourth ophthalmologist was from India—Dr Sunita Agarwal who designed a new probe which incorporates laser and ultrasound in the same pico second (Fig. 36.2).

In 1995 we acquired our first laser machine for cataract surgery. Soon we realized the potential of capitalizing on both the energy sources together, something not thought of by any cataract surgeon at that time. And we developed a probe now capable of utilizing at the same pico second laser and ultrasound energies.

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The instrumentation is thus in two parts. One is the Phaco part that most of us are accustomed too, and the second is the laser part. These may come from the same machine or from two different machines.

The Sunita Agarwal Laser Phaco Probe

All probes used before this (Fig. 36.4) were thus designed that used laser or ultrasound in the innermost circumferential ring, with aspiration and irrigation flowing on the outer ring. This was modified by special intermediary equipment that would allow that phacoemulsification machine to still function with a laser fiberoptic delivery system in its midst. Around this is the ultrasound waves pounding along with irrigation and aspiration flowing on the outside. Thus the whole system consists of a four-function probe. The use and utilization of both energy sources makes it easier for the cataract to be blasted out of the eye in shorter time span, with less energy sources used in the eye. The machine we used was the laser photon machine.

Anatomy of Dr Sunita Agarwal Laser Phacoemulsification Probe

The author has designed this patent pending SA laser phaco probe and it utilizes both, the laser to a maximum extent and ultrasound to a lesser extent for cataract removal. This probe can be developed by passing the laser fiberoptic through the aspiration end of a regular phaco probe. This version of the laser phaco probe gives the advantage of using the laser, ultrasound, irrigation and aspiration. Based on the ablation power of the laser of water containing tissues four main have been evaluated of which Nd: YAG has the lowest capacity for water absorption. It has been further qualified with being near perfect in effect and holds its place in the industry for over two decades. The laser beam is focused onto grades of high tensile glass fiberoptic which carry the same and release it on the cataractous tissue on contact and hence the name contact laser. The laser photoablates 20 microns of cataractous tissue on contact and liquefies a further 200 microns cataractous tissue around it.

Comparison

Let us compare the phaco probe with the laser phaco probe. There is a slight embarrassment to outflow using the laser fiberoptic (Fig. 36.6) in comparison with a phaco probe. This is because the phaco probe is of 900 microns. The laser probe is 380 microns. This is placed inside the phaco

FIGURE 36.5 Phaco incision

FIGURE 36.6 Laser phaco incision

probe. So we get only 520 microns of space left. Still the cataract is removed faster and much more safely.

The laser has the capacity to photoablate 20 microns of tissue space in contact and another 200 microns is liquefied reducing the solid cataract into liquid and gas. The incision size is thus reduced as the phaco handpiece gets hot and can burn the corneal tissue (Fig. 36.5). We are able to perfom laser phaco in an incision of 2 mm (Fig. 36.6). The phaco incision in the cornea can get ragged with corneal burns. This rarely occurs in laser phaco as the phaco energy used is comparatively very small (Fig. 36.7).

As the needle held in the hand is not vibrating anymore it can reach further into the eye without any complications of iris capture or posterior capsule capture. Moreover, the laser is ineffective

of the eye to this energy. This gives the laser cataract removal system an advantage over conventional phacoemulsification systems, with which the ultrasonic energy can vibrate throughout the anterior chamber and involve other ocular tissues.

The laser cataract surgery entails this specially designed probe that combines fluid handling and systems controls of ultrasonic cataract systems, now fortified with the laser energy from a solid state pulsed laser. All three major features of the system irrigation, aspiration and laser are simultaneously transmitted through a precise location in the eye through a single small incision.

The laser is capable of ablating high water containing tissues without pigmented chromophore. This is done causing thermal injury. Its capability of performing these functions through smooth cutting makes utilization inside the eye very favorable. Most ocular tissues are very high in their water content and the laser acts best in these surroundings. Also its high absorption by the cataractous lens makes its unwanted transmission and scatter of laser energy to adjacent and underlying tissues more controlled and precise.

The laser energy is generated through a solid state crystal and its care and service come down to a minimum. The laser is air cooled and does not require any special

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installation practices. Hence it can be transported easily to the end user facility with no untoward engineering practices.

In-built

The laser photon machine has an in-built:

1.Laser,

2.Phacoemulsification system,

3.Vitrectomy system and

4.Diathermy.

Uses

The laser cataract system is used for many purposes:

1.To do a capsulorhexis: This can be done with the help of the laser. One can get a neat round rhexis even in cases of mature cataracts.

2.To remove the nucleus: A combination of laser and aspiration helps remove the nucleus. This is aided by the technique of nuclear chopping. If the cataract is very hard a combination of laser followed by emulsification can be done to make the cataract removal through a 3 mm incision.

3.To remove cyclitic membranes: In such cases even a vitrectomy is difficult as the membrane does not get removed with the help of the vitrectomy probe. But with the help of the laser one can create a central opening in these membranes.

4.To create an opening in glaucoma cases. This is less traumatizing than other routine anti-glaucoma surgeries.

5.To make an inferior iridectomy in cases when vitrectomy is completed and one has to inject silicone oil. In such cases, we normally make the iridectomy with the vitrectomy probe which can by mistake convert a small iridectomy to a complete iridectomy. But with the laser photon one good controlled iridectomy can be created.

Surgical Procedure

The technique is basically the same as in normal phacoemulsification procedures—the only difference being that here instead of ultrasound power one uses the laser energy and very rarely the ultrasound energy also. In the first step a needle with viscoelastic is injected inside the eye to distend the eye. Then a clear corneal incision is done with a diamond knife The rhexis can be done with the laser also. We prefer to do it with a needle. After hydrodissection, the laser phaco probe is passed through the incision, with the phaco chopper in the other hand through the side port opening. The nucleus is circumferentially removed and gradually aspirated out, followed by cortical aspiration, implantation of a foldable IOL and stromal hydration. In stromal hydration the BSS or

saline is injected at the lips of the clear corneal wound hydrating the cornea and making it white. This helps make a better wound closure.

Advantages

•There is no corneal burns or ragged edges at site of the incision as only minimal ultrasound is used in laser phaco as compared to phacoemulsification.

•A smaller incision is enough than that used for Phacoemulsification for cataract removal.

•The titanium needle has a diameter of 900 microns. After threading the laser fiberoptic of 380 microns through the phaco probe, only 520 microns of space is left inside the titanium needle for the rest of the lens material to be removed. But inspite of this embarrassment in space the cataract extraction takes less time than a regular phacoemulsification.

•The laser is ineffective 500 microns away from the posterior capsule and can hence be relied upon while working close to the posterior capsule.

•Capsulorhexis can be safely and neatly performed with the laser.

•This laser has been used in performing laser sclerotomy in cases suffering from glaucoma, to remove cyclitic membranes and to perform iridectomy.

How Small Will Our Incisions Go

Today, with more and more new technology, the Laser Photon will get better and better. It will make the incision size smaller and smaller so that the astigmatism amount becomes much less. By 2000 AD lasers will have become a major force in cataract removal. Foldable IOLs have definitely come to stay and they will improve day by day. Today with the Reliable IOLs the lenses are going through 1 mm incisions.

Any ophthalmologist who wants to put large lenses in large incisions is bucking the tide of history. Small incisions offer the best chance for most rapid, stable visual rehabilitation of the cataract patient at the least cost, including time of impaired vision following surgery, the need for follow-up care, the attendance of relatives to take care of them to the doctor and the like.

It is unclear as to how small will our incisions go—perhaps down to 0.1 mm. With laser phakonit the size has gone to the sub 1 mm incision level. In laser phaconit the laser probe is passed through the titanium tip and the sleeve of the phaco probe is removed. Increasingly, sophisticated laser equipment is capable of giving us better utilization of energy. With the advent of the lasers, the size of the incisions will decrease.

Conclusion

Lasers would revolutionize cataract surgery. This is the modality by which one can go real small in the incision. With this, new techniques and instruments will allow us to put IOLs through these small incisions.

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What the human mind can achieve as it marshals the basic and clinical sciences will continue to amaze us. Look how far we have come regarding IOLs and just imagine how far we will go and can go.

References

1.Thornton SP: IOL’s, knives and lasers: A new commitment to the cataract patient. Proceedings of Ocular Surgery News Symposium, 15:3, 1994.

2.Daniel Eichenbaum: Phaco is easier to do with the new laser system. Ophthalmology Times,

19(13), 1994.

3.Daniel Eichenbaum: New laser phaco. Eye Care Technology, 1994.

4.Jack M Dodick: New laser phaco. Eye Care Technology, 1994.

5.Vance M Thompson: A perspective on balancing the knife with the laser. Ocular Surgery News,

11(13):1993.

6.Daniel Eichenbaum: Laser probes for cataract surgery. Ophthalmology World News, 1995.

7.Daniel Eichenbaum: First computer-aided laser cataract removal system ready for clinical trials.

Ocular Surgery News, 13(9): 1995.