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Cataract Surgery with Dodick Laser Photolysis

Jorge L Alio

Valerio De Iorio

Introduction

The possibility of cataract removal using a laser system has been investigated in the last 15 years as an alternative to the present ultrasound phaco system introduced by Kelman in 1967.1 The first presentation of the idea of laser cataract removal was done by Jack Dodick at the American Academy of Ophthalmology’s 1989 annual meeting2 and in 1991 he performed his first case using a pulsed 1064 nm Nd: YAG laser.3,4 The technique was presented as an alternative of the ultrasound phacoemulsification. As a matter of fact, even if the effectiveness of the ultrasound phacoemulsification with all degree of nuclear density is well known, this technique is not free of drawbacks, complications such as burns at the wound, the potential damages of the endothelial cells, of the iris, the mechanical trauma due to the turbulence of the fluids and the nuclear fragments specially of hard cataracts and the always present risk of posterior capsule breaks.5

Technical Fundamentals of Laser Photolysis System

Up to now only two solid-state laser system are available for cataract removal: The neodymium: yttrium aluminum garnet (Nd: YAG) laser, and the erbium: YAG (Er: YAG) laser.5

The systems using the Nd: YAG laser are divided in: (i) direct acting system (Photon, Paradigm Medical Industries, Salt Lake City, UT), and (ii) indirect acting system {(Dodick laser lens ablation device, ARC laser GmbH, Germany) Fig. 38.1}.

The Nd: YAG laser principle has been used for

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FIGURE 38.1 Dodick’s ARC laser system

FIGURE 38.2 View of the titanium target inside the laser tip

many years in YAG capsulotomy and is based on the generation of plasma and shock waves. Specifically the laser-pulsed energy is transmitted from the source by a Quartz fiber of 300 µm through the handpiece, stopping 1.3 mm in front of the Titanium target inside the tip (Fig. 38.2). This target acts as a transducer converting light energy into mechanical energy (shock waves). As soon as the light strikes the titanium target, an optical breakdown (plasma formation) and shock waves result which disrupts the nuclear material held at the mouth of the aspirating port. In this way there is no light leakage potentially dangerous for the retina, corneal endothelium and for the eyes of the surgeon.6–9

FIGURE 38.3 Laser phaco lysis handpiece and two port side irrigation cannula

On the bases of recent studies, comparing the heat produced at the US phaco tip and at the laser phaco lysis tip, it has been proved that the laser system produces no clinical significant heat in respect to what happens in the US phaco system,10 for this reason there is no need of a cooling system. The previous model of handpiece, that included besides the Quartz fiber and aspiration line the infusion line, now is formed only by Quartz fiber and aspiration (Fig. 38.3). In this way the purpose of reducing both the handpiece dimensions and the diameter of the tip and obviously the incision size is reached. Consequently, the surgical approach has been modified from unimanual to bimanual configuration, in which the infusion connected with a conventional I/A phaco system, better with Venturi-based pumps is introduced through a second paracentesis.11 Actually the diameter of the tip is 1.2 mm and the wound size to implant a foldable IOL has to be enlarged up to 3.4 mm.

Selection of Patients and Indications

Up to this moment the cataract density that we are able to treat range from +1 to +3.

The hard cataract of more than +3 or +4 and harder, for the moment remain treatable in our hands, only with the US phacoemulsification. We found that an optimal elective indication nowadays of Dodick’s laser photolysis is for lens refractive surgery.

Considering the very delicate way of working of this device, other excellent indications are subluxated cataractous lenses and post-traumatic cataracts of not high density, zonular laxity and some congenital cataracts.

Anesthesia

•Topical anesthesia: Generally, the laser photolysis, can be done using topical anesthesia

0.75percent bupivacaine plus 2 percent lidocaine 2 drops every 5 minutes before surgery, with supplemental intracameral preservative-free 1 percent lidocaine diluted

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1:1 in balanced salt solution (BSS). Additionally we can use to add sedation with 1 mg ½ of Dormicum and 0.5 mg of Limifen, upon patient needs.

However, we may prefer to use other anesthesia options in order to eliminate intraoperative eye movements, especially in young anxious patients and according to the surgeon’s preference.

•Peribulbar anesthesia with 8 cc of 0.75 percent, bupivacaine and 2 percent lidocaine plus Tiomucase to help the diffusion in the orbit: Special attention should be taken in the anesthesia of high myopic eyes with posterior staphyloma. Mild venous sedation is used when necessary, specially to decrease the pain sensation during the injection of the anesthetic solution. In this case we use 1 mg per kg of Propofol EV.

•Retrobulbar anesthesia has been abandoned in our hands, specially in the elongated myopic eye, due to the risk of globe perforation.

•General anesthesia is not necessary unless requested as in very young patients.

•Sub-tenonian anesthesia with blunt Fukasaku cannula (Katena, products. Inc. Denville; New Jersey, USA. Ref. K7–4002) of 1 percent lidocaine, provides an alternative option specially with sclerocorneal approach in high myopes.

Then a light compression with the Honan balloon is applied for 5 minutes, 15 minutes before surgery.

FIGURE 38.4 First paracentesis with a 1.4 mm calibrated blade at 2 O’clock position

Surgical Technique with Dodick Laser Phacolysis: Our Experience

We have operated 45 patients with this device with cataract density of +1/+3, and all except the first five cases, under topical anesthesia. We perform first two watertight paracentesis in clear cornea 90° apart, at 10 and 2 O’clock with 1.4 mm blade (V-Lance Knife, Alcon Surgical, Fig. 38.4) followed by the injection of 1 percent lidocaine preservative-free diluted 1:1 in BSS. Two different viscoelastic solutions are used in the anterior chamber, first Viscoat (Alcon Cusi’, Barcelona, Spain) to protect the endothelium, then Celoftal (Alcon Cusi’, Barcelona, Spain) to increase volume in the

anterior chamber (AC). A 5.5 mm continuous curvilinear capsulorhexis (CCC), is performed with Condon capsulorhexis forceps (John Weiss, Milton Keynes, England. Ref. 0101566), which is the only one that we have found effective through the watertight incision (Fig. 38.5). After the hydrodissection of the cortex and nucleus with a flat cannula, we introduce first the irrigation cannula with two-port side, at 2 O’clock incision, then the phaco laser tip at 10 O’clock incision. The laser lysis of the cataract can be described as “touch, pulse, aspiration”.11 In fact the ablation of the nucleus begins applying

FIGURE 38.5 Continuous curvilinear capsulorhexis (CCC) with Condon forceps through the 1.4 mm incision

lightly the probe on the anterior surface of the cataract then a pulse of laser is delivered at the lower laser set power with vacuum level of 250 mm Hg using the Venturi pump of the Accurus device (Alcon Ref. 8065740238): and the fragment is aspirated (Figs 38.6A and B). We have found less effective the peristaltic pump used previously in our initial cases. The nucleus is cracked after creating a deep initial groove, as soon as is possible. When all the nucleus is aspirated, we insert at 10 O’clock position the aspiration cannula decreasing the vacuum till 100 mmHg and we finish to clean the cortex remnants (Fig. 38.7). After the injection of a dispersive cohesive viscoelastic solution like methylcellulose Celoftal (Alcon Cusi’, Barcelona, Spain) in the capsular bag, we enlarge the 10 O’clock incision up to 3.2 mm and we implant a foldable IOL (Figs 38.8A and B). The procedure terminates with the aspiration of the viscoelastic solution using specific I/A cannula (Geuder, GmbH, Heidelberg, Germany. Ref. G-32774; G-32769) in continuous irrigation and hydrating the two wound with BSS (Figs 38.9 and 38.10).

The reason why we perform two watertight incisions is because this procedure utilizes high vacuum, so it is necessary to work in a closed pressurized surrounding, the only drawback is the needs to screw a bit the tips into the incision.

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FIGURE 38.6A Laser lysis and aspiration of the nucleus

FIGURE 38.6B Aspiration of cortical material

Usually with +1/+2 density cataracts, 40 to 100 pulses are sufficient to complete the procedure, while with +3 density we use about 300 to 400 pulses. The bottle of BSS is fixed 75 cm high from the patient’s head.

If placed at a higher level, the excessively high intraocular pressure (IOP), may induce initial vagal response to the patient due to the induction of oculo-vagal reflex.

FIGURE 38.7 Cleaning of the cortical cells with the aspiration cannula

FIGURE 38.8A Implantation of a foldable IOL with Buratto IOL folder forceps, after enlarging the incision up to 3.2 mm

Transition from Phacoemulsification

The transition from the US phacoemulsification to the photolysis system is easy, the surgeon has only to be customized on working in a pressurized anterior chamber.

Converting into Phacoemulsification

If for any reason the surgeon has to interrupt the photolysis technique, for instance when the nucleus is harder than what he expected, before entering with the phaco tip, he has first to enlarge the 10 O’clock incision up to 3.2 mm, then to avoid the anterior chamber collapse due to the excessive

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FIGURE 38.8B Implantation of an injectable acrylic IOL, after enlarging the incision up to 3.2 mm

FIGURE 38.9 Aspiration of viscoelastic solution with I/A cannulas

outflow of fluidics, has to stitch the 2 O’clock paracentesis. In this way, it is possible to complete the operation as the usual phacoemulsification.

Cataract Surgery and Clear Lens Extraction in High Myopia with Photolysis Laser System: Our Technique

In high myopic patients, in whom we implant a non-foldable IOL, the AL-3 (Domilens, Chiron Vision, Lyon, France) we use a scleral approach.

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traditional ultrasound phacoemulsification. In this regard Dodick referred that in his last series of cases, he found that the endothelial cell loss ranged from 0 to 6 percent, and no change in corneal thickness following the procedure occurred.5

Posterior Capsule Rupture

In our experience we had only two cases of capsular breaks due to the use of the highlaser power setting used in soft cataracts. Generally no specific postoperative complications happened to our cases, anyway we cannot refer any about other surgeon’s experiences. No other complications were observed. Corneal edema, even minimal, was never observed at the slit-lamp examination, even at the early postoperative period.

Advantages and Disadvantages

This system appears to be safer for the corneal endothelial cells, for the posterior capsule, and the iris. Practically no heat production is produced and there are no corneal burns. The ergonomic shape of the handpiece gives to the surgeon a more comfortable way of working. Moreover we emphasize the low energy and the low fluidics used, the stability of the anterior and posterior chamber during the procedure, the quietness if compared to the traditional phacoemulsificator device and most important of all the “minimal” incision surgery (less than 2 mm), VS the “small” incision surgery (more than 2 mm). The procedure itself has low cost, considering the quartz fiber, the handpiece and the disposable titanium target. For the moment only the laser system has high cost. Technically the only limitation is the hard cataract.

Future Trends

The big target pursued by all the surgeons to perform a cataract operation with the “Minimal” incision, seems finally to be catch, and the old dream of injecting a malleable, clear polymer trough a small capsulotomy, capable of accommodation, brings to our memory the Phacoersatz idea.13 Now the biggest effort has to be done by the company interested on inert polymer that could really mimic the human lens and its characteristic accommodation ability. We can imagine that the new kind of IOLs, could be liquid, injectable and made of silicone, hydrogel or collagen.11

Summary

More than 20 years have passed since Kelman introduced the US phaco system,1 till Dodick presented his first laser phacolysis cataract extraction.2–4 From that moment different types of phaco lasers have been tried. Actually only two-laser system are used for this purpose: (i) the Nd: YAG laser, and the Er: YAG laser. Our personal experience is referred to the Dodick laser photolysis device. The undoubted advantages (Table 38.1) of this technique are: the minimal incision, the safety for the endothelium, the very low

rate of posterior capsular rupture, no heat production at the tip and consequently no corneal burns, the very delicate and controllable way of cataract removal, the minimal or practically absent intra/postoperative complications and the safe and fast learning curve. The main technical limitation is represented by the high-density cataracts. Today the most important indication seems to be the surgical treatment of high degree of refractive errors through clear-lens extraction and IOL implantation (phaco refractive cataract surgery). Our experience with high myopic patients, seems to confirm the suitability of this device in order to avoid any complications in treating this particular kind of eyes.12 Because of the safety of this technique, other indications could be—subluxated lens, zonular laxity, post-traumatic cataracts and congenital cataracts. Now, to make use properly of the advantages brought by this “Minimal incision surgery”, we must wait for the technical improvements in the development of new IOLs materials.

References

1.Kelman CD: Phacoemulsification and aspiration—a new technique of cataract removal, a preliminary report. Am J Ophthalmol 64:23–35, 1967.

2.“Use of Neodymium-YAG laser for removal of cataracts is reported”. Ophthalmology Times 1:1989.

3.“First Laser Phacolysis proves a success”. Ophthalmology Times, 1991.

4.Dodick JM, Sperber LTD, Lally JM et al: Nd: YAG laser phacolysis of human cataractous lens—a case report. Arch Ophthalmol 111:903–04, 1993.

5.Aasuri MK, Basti S: Laser cataract surgery. Current Opinion in Ophthalmology 10:53–58, 1999.

TABLE 38.1 Dodick’s photolysis laser system: settings (Prof. Jorge L. Alio’, Instituto Oftalmologico de Alicante)

6.Dodick JM: Laser phacolysis of the human cataractous lens. Dev Ophthalmol 22:58–64, 1991.

7.Dodick JM, Lally JM, Sperber LTD: Lasers in cataract surgery. Current Opinion in Ophthalmology 4(1):107–09, 1993.

8.Dodick JM, Cristiansen J: Experimental studies on the developement and propagation of shock waves created by the interaction of short Nd: YAG laser pulses with a titanum target—possible implications for Nd: YAG laser phacolysis of the cataractous human lens. J Cataract Refract Surg 17:794–97, 1991.

9.Lewin PA, Bhatia R, Zhang Q et al: Characterization of optoacoustic surgical devices. IEEE Transaction on Ultrasonics, and Frequency Control 43(4):1996.

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10.Alzner E, Grabner G: Dodick laser phacolysis: termal effects. J Cataract Refract Surg 25:800– 03, 1999.

11.“Laser Lens Lysis—a new approach to very small incision cataract surgery” Cataract and Refractive Surgery Euro Times, 6:1997.

12.Dorothy SP Fan, Dennis SC Lam, Kenneth KW Li: Retinal complications after cataract extraction in patients with high myopia. Ophthalmology 106:688–92, 1999.

13.Haefliger E, Parel JM, Fantes F et al: Accommodation of an endocapsular silicone lens (phacoersatz) in non human primate. Ophthalmology 94:471–77, 1987.