Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001

492 THE ART OF PHACOEMULSIFICATION

What we are doing is different. We are first of all performing a vitrectomy. We have now converted the vitreous into saline or BSS depending on the irrigating fluid being used. The nucleus is now lying on the retina surrounded by fluid. In other words, the retina is akin to the posterior capsule. It is just like the nucleus lying on the posterior capsule surrounded by aqueous humor or fluid.

Now, what we are doing is just taking of the nucleus like we would do it in the anterior chamber. We are using suction and then very little phaco power to embed the nucleus. The nucleus is brought anteriorly and then removed. The chances of tears occurring in the retina are not there because we have first converted the vitreous into fluid. Another point to note is since we are doing a two port vitrectomy we need not make the third port, which makes things messier. This is the reason why we use the peristaltic pump of the phaco machine and not a separate venturi

vitrectomy machine.

REFERENCES

1.Paris CL, Peyman GA, Blinder KJ et al: Surgical technique for managing rhegmatogenous retinal detachment following prosthokeratoplasty. Retina 11: 301-04, 1991.

2.Michael J Shapiro, Kenneth I Resnik et al: Management of the dislocated crystalline lens with a Perfluorocarbon liquid. Am J Ophthalmol 112: 401-05, 1991.

3.Lewis H, Blumenkranz MS, Change S: Treatment of dislocated crystalline lens and retinal detachment with Perfluorocarbon Liquids. Retina 12: 299-304, 1992.

4.Magherio RR, Magherio AR, Pendergast SD et al: Vitrectomy for retained lens fragments after phacoemulsification. Ophthalmology 104: 1426-32, 1997.

5.Fastenburg DM, Schwartz PL, Shakin JL et al: Management of dislocated nuclear fragments after phacoemulsification. Am J Ophthalmol 112: 535-39, 1991.

6.Borne MJ, Tasman W, Regillo C et al: Outcomes of vitrectomy for retained lens fragments. Ophthalmology

103:971-76, 1996.

7.Lambrou FH (Jr), Stewart MW: Management of dislocated lens fragments during Phacoemulsification.

Ophthalmology 99: 1260-62, 1992.

8.Kapsuta MA, Chen JC, Wai-Ching Lam: Outcomes of dropped nucleus during Phacoemulsification.

Ophthalmology 103: 1184-87, 1996.

9.Gilland GD, Hutton WL, Fuller DG: Retained Intravitreal lens fragments after cataract surgery.

Ophthalmology 99: 1263-69, 1992.

10.Topping TM: Retained intravitreal lens framgments after cataract surgery (Discussion). Ophthalmology

99:1268, 1992.

11.Blodi BA, Flynn HW (Jr), Blodi CF et al: Retained nuclei after cataract surgery. Ophthalmology 99: 4144, 1992.

12.Rowson NJ, Bacon AS, Rosen PH: Perfluorocarbon heavy liquids in the management of posterior dislocation of the lens nucleus during phacoemulsification. Am J Ophthalmol 76: 169-70, 1992.

13.Movshovich A, Berrocal M, Change S: The protective properties of liquid perfluorocarbons in phacofragmentation of dislocated lenses. Retina 14: 457-62, 1994.

INTRODUCTION

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.

Pioneers

For decades now we have known benefits of the ultrasound energy. Incorporated with Dr Kelman’s path breaking inroads of using this energy for the removal of cataracts has indeed reduced rehabilitation of the cataract patient.

Four top opthalmologists1-7 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 fiberoptically 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.

494 THE ART OF PHACOEMULSIFICATION

The third ophthalmologist is Dr Michael Colvard. The erbium (Er) 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 nonpercussive 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.

The fourth ophthalmologist is from India—Dr Sunita agarwal who has designed a new probe which incorporates laser and ultrasound in the same pico second.

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.

Instrumentation

An ordinary phaco unit would contain three functional elements, the phaco power delivered through a vibrating titanium needle of 900 microns diameter, aspiration through the needle, and irrigating fluid pump into the eye through a silicon sleeve.

The laser unit consists of a key switch screwed into the laser head unit that allows the laser light to pass through a glass fibreoptic delivery and the aiming beam is also passed through the same system. This fibre is of 380 microns in diameter.

The laser phaco probe developed by Dr Sunita Agarwal is patent pending as the idea of incorporating laser with ultrasound in the removal of cataracts was first developed by us and after going through many experimentations and variations we now plough the laser fiberoptic through the phaco probe making any phaco probe into a SA (Sunita Agarwal) laser phaco probe (Fig. 46.1).

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 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.

LASER PHACO CATARACT SURGERY 495

Fig. 46.1: SA (Sunita Agarwal) laser phaco probe

Comparison

Let us compare the phaco probe with the laser phaco probe. There is a slight embarrassment to outflow using the laser fiberoptic in comparision 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 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. We are able to perfom laser phaco in an incision of 2 mm.

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.

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 500 microns away from the posterior capsule and can be used very close to the capsule.

The laser used is an Nd: YAG with fibreoptic delivery and only the cataractous tissue needs to be removed thus leaving behind an epinucleus and cortex that can be easily aspirated.

Laser Photon

In the laser photon pulsed laser energy is used to vaporize and aspirate the lens material out of the eye (Table 46.1). The most important feature of the Laser Photon is its containment of laser energy. The probe is so designed that energy used to emulsify the cataract is contained in a photovaporization chamber. The energy used to remove the cataract does not expose the contents of the eye to this energy. This gives the laser cataract removal system an advantage over conventional phacoemulsification systems (Tables 46.2 and 3), 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 ultilization 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 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 in-built:

•Laser

•Phacoemulsification system

•Vitrectomy system

•Diathermy.

Uses

The laser cataract system is used for many purposes:

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

•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.

•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.

•To create an opening in glaucoma cases This is less traumatizing than other routine antiglaucoma surgeries.

•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.

LASER PHACO CATARACT SURGERY 499

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.

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. With Laser Phakonit we have broken the 1 mm barrier. 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 renal small in the incision. With this, new techniques and instruments will allow us to put IOLs through these small incisions.

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: IOLs, Knives and lasers—a new commitment to the cataract patient. Proceedings of Ocular Surgery News Sysmposium. 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:L 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.