Cool laser blasts way to micro-incision cataract surgery

By Roibeard O'hÉineacháin

NICE - Cataract extraction using the Dodick Laser PhotolysisTM system (ARC, Switzerland) is as fast as conventional ultrasound phacoemulsification and allows the surgeon to work with ultra-small incisions with minimal trauma and no risk of burns to the eye.

More than that, new specially designed IOLs also allow for completion of the procedure without enlarging the wound, inventor and developer Jack Dodick MD, FACS told the XX ESCRS Congress.

He noted that the Dodick Laser Photolysis system is now being used in over 100 centres worldwide and over 5,000 cases have been performed with it. It is currently the only FDA-approved laser system for cataract removal.
"The Dodick Laser Photolysis system for cataract removal should no longer be categorised as experimental or investigational but as alternative to ultrasound phacoemulsification," he asserted.

The laser cataract removal system uses an indirect Nd:YAG laser to generate shock waves by striking a titanium target at the end of an aspirating hand piece.
The flexible quartz fibre probe does not generate heat, which eliminates the risk of corneal burn. As a result, the probe may be inserted through a 1.4 mm or smaller incision, since no sleeve is necessary.

New intraocular lenses which can be inserted through such tiny incisions have provided further impetus for the adoption of the micro-incision technology, Dr Dodick pointed out.
He noted, for example, that German specialist Wolfram Wehner MD currently performs 80% of his cataract procedures from beginning to end with ultra-small incisions using Dodick Photolysis and AcriTec™ IOLs which he inserts without enlarging the wound.

"Before these new lenses were available, people would ask what the advantage was of being able to remove a cataract through a 1.4 mm incision when you are going to have to implant the lens through a 3.0 mm.

"Now, like history repeating itself with ultrasound phacoemulsification, there is a small-incision lens and that is an excellent motivation to adapt to the newer technology," he said.
Dr Wehner uses a bi-manual procedure. He inserts the combination laser/aspiration probe, which has an outside diameter of 1.2 mm, through a 1.4 mm incision.

In a second 1.4 mm incision, he inserts a special irrigating chopper which he designed himself called the Wehner Spoon, Dr Dodick explained.
In his first 849 cases using the Dodick photolysis system, Dr Wehner was able to complete the procedures in cataracts between grades one to four from beginning to end in under 10 minutes and in grades one to two in nine minutes or less.

"One of the biggest misconceptions about laser cataract surgery is that all lasers are the same and it is slow. It is not, at least with this technology, and the procedure time drops dramatically with new high vacuum tubing advances.
"So I can make a categorical claim that this procedure is as fast and sometimes faster in 1+ and 2+ cataracts," Dr Dodick said.

In addition, the laser system releases very little energy into the eye. In 225 consecutive cases measured by Andrew Miller MD in New York, 185 cataract extractions required 1.0 J or less of laser energy, 38 required 1.0 J to 2.0 J and only two required more than 2.0 J.

"The only report in the literature concerning ultrasound energy is a four-year-old study by DeVries and at that time cataract extractions involved between 700 J and 1,100 J depending on the technique.

"I'm sure that has dropped tremendously with the focus on high vacuum but the input energy with the laser cataract removal really is infinitely small," Dr Dodick noted.
The Dodick Laser Photolysis system has a Venturi phacoemmulsifation unit. It also has combined features for posterior segment surgery including vitrectomy light pipe and silicone oil injection.

Recent modifications include a smaller 0.9 mm probe now undergoing beta testing that may be inserted through a 1.0 mm incision. The new probe is completely disposable after one use and should become available in the first quarter of 2003.

Another advance which has now been implemented is new high vacuum tubing. The tubing provides greater vacuum creation and 'hold' with less total fluid flowing through the eye and has increased both the efficiency and safety of the procedure.
"Most of the publications on endothelial cell loss after ultrasound phacoemulsification are based on the premise that it correlates with the amount of energy put into the eye but I don't think that that is necessarily so. I think the amount of fluid passed through the eye is a contributing factor," Dr Dodick said.

One surprising and as yet unexplained possible advantage the laser system may have over ultrasound is a reduced rate of posterior capsule opacification (PCO).
In a study carried out by Lindsey Smithen MD in New York, the PCO detection and treatment rates in 100 eyes undergoing cataract removal with Dodick Photolysis were only 1.0%. That compared with PCO detection and treatment rates of 7.5% in 100 eyes undergoing conventional ultrasound phacoemulsification.
"We don't know why this occurs but we are investigating it further. Perhaps the laser also has an effect on the germinal epithelium in the equatorial zone of the eye.

"And while these are early days, it's worth pointing out that we have here a technology that could enable us to purposely ablate the germinal epithelial cells in the periphery after cataract removal. In this way, we might perhaps cure PCO and that's very much on our front burner right now," Dr Dodick said.

One argument against learning to operate the Dodick Laser Photolysis system is the development of enhanced forms of ultrasound phacoemulsification which also allow for micro-incision cataract removal.
Several proponents of such systems voiced their scepticism about the usefulness of the laser method when ultrasound can achieve the same results and do so in cataracts of every degree of hardness.

Spanish ophthalmologist, Carlos Verges MD told the conference that he has used all three types of laser cataract removal procedures - the Dodick Photolysis System, the Nd:YAG laser direct ablation and the erbium laser.
However, in his opinion the broader applicability of newer ultrasound systems, particularly the AMO Sovereign WhiteStarTM, made them easier to use than the laser systems.

"For me, the best arrangement is the one that is most simple. If I have one system that enables me to perform all kinds of cataracts, it is better. We complicate all our surgery if we need more than one system even if it is in the same place," Dr Verges said.
Richard Packard MD, who is also a proponent of the WhiteStar, concurred with Dr Verges and suggested that the time when laser could have contributed in a useful way to cataract surgery may have already passed.

"I think we need to analyse why laser phacoemulsification exists at all. The first time I saw Dr Dodick describe the procedure was actually in the late 1980s. It was of interest then because of the way ultrasound was performed at that time and because laser at that stage was going to give us the possibility of small-incision surgery.

"Since that time ultrasound has moved on and as a result most if not all of the arguments for laser cataract removal have virtually disappeared," Dr Packard said.
Israeli ophthalmologist Ehud Assia MD suggested the strongest point in favour of laser cataract removal was its novelty.

"Currently, the only advantage for laser machines is their name. Patients love lasers. Otherwise, ultrasound does better in all other parameters but the future will tell which type of system prevails," Dr Assia said.

Dr Dodick countered these arguments by pointing out that his laser system is a rapidly developing technology and can already perform as well if not better in the removal of most cataracts. In addition, he noted that the reduction of energy, less risk of PCO and absolutely no risk of corneal burns were advantages that could not be denied nor for that matter could be deliverable by ultrasound.

Many surgeons are using the WhiteStar programming with a sleeve and many have noted that their wounds seal better. This re-introduces the idea of low-grade corneal burns existing at a higher rate than clinically noted and may be a source of unexpected postoperative astigmatism.

"I'm a student of history and ultrasound was invented at my hospital by Charlie Kelman in 1967. I was there on the day the first ultrasound procedure took 61 minutes of ultrasound time and four hours and five minutes of surgery.

"Many surgeons took the position that there was no reason to bother. The remarks of Dr Packard remind me so much today of those same comments made of phacoemulsification some 35 years ago. So I have the patience to develop and adopt a promising new technology," Dr Dodick said.

He added that it will not be for a handful of ophthalmologists to decide which technology will bring true reproduceable microincision cataract surgery. The best technology will obviously prevail, he said.

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