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Erbium laser cataract surgery is now bimanual, easier and safer to perform
Phacoemulsification is performed through a 1-mm incision, with a newly designed tip for better aspiration.
VENICE, Italy — The most recent prototype of Er:YAG laser (Phacolase; Asclepion-Meditec AG, Jena, Germany) allows a more effective and even safer emulsification of the lens in laser cataract surgery. Alessandro Franchini, MD, one of the pioneers of the technique, spoke about its latest improvements at the Venice 2000 meeting here.
“The advantage of erbium over other types of laser energy is that its 2.94 µm wavelength corresponds to the maximum peak of water absorption. Since in the eye we are working in water, the erbium laser gives us the safety of low penetration [about 1 µm] without energy dispersion in the surrounding tissues,” Dr. Franchini said.
Improved delivery system
---The new tip for laser phaco is tapered to prevent obstructions.
“We have been consistently performing laser cataract surgery with the erbium YAG laser for more than 5 years now and have been able to progressively introduce significant improvements, both in the technique and in the hardware and software of the machine,” Dr. Franchini said.
Whereas the first prototype worked on a low frequency and high energy rate, the latest has inverted the proportion between the two values. The repetition rate is variable between 10 and 100 Hz, the energy rate between 10 and 50 mJ.
“We have progressively lowered the energy and increased the frequency, as this produces considerable advantages,” he said. “With an increased frequency, the laser works more as a continuous laser, allowing a better adherence of the fragments to the tip and a good vacuum.”
Important modifications also have been introduced in the design and materials of the handpiece.
A crucial step was the choice of the best fiber to transmit the energy from the source to the delivery system.
“Zirconium fluoride is the best known material to transmit infrared radiation,” Dr. Franchini said. “However, it has the disadvantages of toxicity and poor flexibility.”
The problem was overcome by changing the end section of the fiber with a quartz fiber. “Quartz is non-toxic, biocompatible, flexible and cheap. It is only a small portion of the fiber so that only a low attenuation of the laser transmission is produced.”
The design of the tip also has been changed. The new version presents a tapered end that resolves all obstruction and aspiration problems.
“With the old design, fragments could easily be trapped inside the tip, especially where the aspiration tube was curved,” Dr. Franchini said. “With this new tapered tip, the entrance is the narrower part of the system, and fragments that are aspirated will never be large enough to cause obstruction.”
Bimanual technique
--- Capsulorrhexis can be performed using the laser.
From 1995 to 1997, Dr. Franchini participated with two other centers in Europe in a pilot study, which allowed the Phacolase to obtain CE marking. Following an international protocol, all the operations were performed with a monomanual technique. After the conclusion of the project, Dr. Franchini has switched to a bimanual technique.
Two paracenteses of 1 mm are performed at the 2-o’clock and the 10-o’clock positions. A capsulorrhexis is performed with a needle, with specially designed forceps or with the laser tip.
“I believe the needle is still the best choice,” Dr. Franchini said. “Both the laser tip and the forceps require a slightly wider incision. A 1.5-mm incision makes no difference in terms of postoperative astigmatism. However, it is not as watertight as a 1-mm incision when using, as we do, a sleeveless tip. And this can create serious problems in maintaining the anterior chamber depth.”
As the surgeon explained, in laser phacoemulsification, the capsulorrhexis should be larger than in ultrasound phacoemulsification, to avoid contact of the tip with the rhexis edge in the following stages of surgery.
“Even the slightest contact of the laser tip would tear the edge of the capsulorrhexis. It happened to me six times during the pilot study,” he said.
When performing laser capsulorrhexis, a high frequency and low energy rate is applied to avoid mini tears. In this way, the pulsed mode of the laser is almost transformed into a continuous mode, and a smooth, continuous rhexis can be obtained.
“We haven’t yet discovered the perfect technique for laser phacoemulsification,” Dr. Franchini said. “At present, the classical divide-and-conquer is still the safest option. More advanced techniques need a higher vacuum, which we are still unable to provide. However, as the new tip has an increased aspiration power, experienced surgeons also can try a phaco-chop technique, especially when operating very hard nuclei.”
The final target of laser cataract surgery is an IOL that can be fitted through a 1-mm incision. An injectable lens will be the solution in years to come. So far, the market offers intermediate solutions, which allow a minimal enlargement of the incision.
Dr. Franchini uses a 5.5-mm foldable silicone IOL (STAAR [Monrovia, Calif.] Model AQ 2017V/AA 4207VF) that can be fitted through a 2.5- to 2.7-mm incision.
Latest results
---The divide-and-conquer technique is still the safest method for bimanual laser phaco.
A total of about 400 patients have been operated with the Phacolase by Dr. Franchini. He presented the clinical results obtained in a group of 58 patients operated between 1998 and 1999 with a bimanual technique and a follow-up of almost 6 months. Patients were chosen at random, so that their cataracts were at different stages of development.
Emulsification time, pulse rate and energy rate were closely related to nucleus hardness.
The average emulsification time was 4 minutes and 48 seconds, ranging between a minimum of 1 minute and 6 seconds and a maximum of 18 minutes and 32 seconds. The average number of spots was 3,114, ranging between 840 and 14,320. The average energy was 31.1 J, ranging between 8.4 J and 143.3 J.
“The average energy we used is 10 to 100 times less than what is needed with ultrasound,” Dr. Franchini said.
More than 6 months after surgery, the mean endothelial cell loss was 2.123%.
Corneal thickness was measured immediately before surgery and at day 1 postop. The average increase was 5.82%. The difference with the average increase of a control group of patients who underwent ultrasound phacoemulsification (9.101%) was statistically significant (P<.005).
“Our results confirm that laser phacoemulsification is no longer confined to pure experimentation, but is now playing an important role in everyday clinical practice,” Dr. Franchini said.
“Opinions also have gradually changed in the past few years. Five years ago, there was a lot of skepticism regarding the possibility of using laser rather than ultrasound in cataract surgery. Nowadays, both surgeons and companies are showing an increasing interest in it.”
Venice 2000 was sponsored by Ocular Surgery News, the Italian Association of Cataract and Refractive Surgery and the International Society of Refractive Surgery.
For Your Information:
- Alessandro Franchini, MD, can be reached at works at Istituto di Oculistica, Università di Firenze, Viale Morgagni 85, 50134 Firenze, Italy; (39) 055-411765; fax: (39) 055-4377749; e-mail: oculist@cesit1.unifi.it. Dr. Franchini has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.