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‘Cold’ ultrasound MICS as safe as laser and effective as standard phaco, surgeon says
Study shows that so-called cold ultrasound is quick and efficient in removing hard nuclei.
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| “Cold” ultrasound microincision cataract surgery. Erbium laser microincision cataract surgery. Microincision cataract surgery with WhiteStar produces a low increase in temperature of the tip. Images: Franchini A |
FLORENCE — “Cold” ultrasound microincision phacoemulsification with the Sovereign with WhiteStar system is a promising technology for cataract surgery, according to Alessandro Franchini, MD, of Florence University Eye Hospital.
“It combines the safety of laser with the efficiency of standard ultrasound phaco and maintains the same level of performance over the entire range of nucleus hardness,” he said.
In a study, Dr. Franchini compared the results of this technique with laser phaco using an Er:YAG laser.
“Back in the early ’90s, I was one of the first advocators of erbium laser phaco because it allowed for a truly small, astigmatically neutral incision. However, I was aware that the technique could only work for soft nuclei. With +2 nucleus density, the procedure could take three times longer than standard ultrasound phaco,” he said.
In 2002, when it was demonstrated that a rapid sequence of microbursts and microrests with the WhiteStar system on the Advanced Medical Optics Sovereign phaco system could significantly reduce the amount of ultrasound energy and heat delivered to the eye, Dr. Franchini tried the new technique and was enthusiastic about its results.
Comparing procedures
The study compared the outcomes of 81 sleeveless bimanual MICS procedures using the Sovereign with WhiteStar technology with results from 206 eyes operated with the Phacolase MCL 29 Er:YAG laser system (Asclepion Meditec).
In both groups, the surgery was performed through 1-mm incisions.
For the ultrasound procedures, Dr. Franchini said a new set of instruments was designed to operate through watertight incisions.
A trapezoidal tunnel rather than a rectangular one was created for easier and safer maneuvering in the anterior chamber. Capsulorrhexis was performed either with a needle, special forceps or an erbium laser.
“Through 1-mm incisions, thermal capsulorrhexis is easier and safer, but there is a higher risk of capsule breaks during phacoemulsification,” he said.
Nucleus fragmentation was performed with a phaco-chop technique, which helped maintain a constant irrigation flow. Dr. Franchini said he found that a rounded-tip irrigating chopper allowed greater safety.
In both groups, the incision was enlarged to 2.7 mm after phacoemulsification to insert the IOL. The AMO Sensar with OptiEdge was used in all patients and inserted with the Unfolder Emerald injection system.
Significant time difference
Equivalent phaco time (EPT) was compared to laser time, and visual outcome, endothelial cell count and corneal pachymetry were compared between the two groups.
“The difference in average phaco time was highly significant between the two groups. It amounted to 4.6 seconds (range 0.5 to 18.7 seconds) in the ultrasound group and to 1 minute and 48 seconds (range 11 seconds to 18.5 minutes) in the laser group. In both groups the EPT was closely related to the hardness of the nucleus, but the ultrasound system remained efficient when compared with dense nuclei, although very low levels of energy were used. With the laser procedure, the additional time required for nuclei +3 to +4 was incomparably longer,” Dr. Franchini said.
No significant differences were found for the other parameters. Uncorrected visual acuity at 1 day and 3 months was comparable, corneal edema was observed in about 15% of the patients regardless of the technique used, and the increase in corneal thickness the day after surgery was similar in the two groups. Endothelial cell loss at 6 months was just over 2% in both groups.
One of the main concerns regarding sleeveless ultrasound surgery is the possibility of producing corneal burns at the incision site. The Phacolase was safe, Dr. Franchini said, because after 30 seconds of continual use in normal conditions, the temperature of the tip increased by only 2.6°C, compared to 30°C in 30 seconds of old standard ultrasonic devices. However, the WhiteStar technology was found to have comparable safety standards because the temperature at the phaco tip also increased by about 2°C to 3°C and always remained below 42°C, he said.
“Below this temperature, there is no risk at all that corneal burns, corneal shrinkage or haze may occur,” he noted.
Surgical tips
Dr. Franchini said that most surgeons can perform ultrasound microincision surgery and that no learning curve is needed to switch from one-handed to bimanual technique. However, some adjustments are required to adapt the usual surgical maneuvers to a smaller incision.
“Above all, it is important to ensure that incisions are perfectly watertight throughout the procedure to maintain a stable chamber. The irrigating chopper should constantly provide sufficient irrigation. Avoid highly cohesive viscoelastics that could increase ocular tension, and remove the substance completely before you begin hydrodissection. At the end of the procedure, remember to remove the phaco tip before the irrigating chopper to prevent anterior chamber collapse,” he said.
Dr. Franchini said he believes ultrasound MICS is “the best and definitive solution from every point of view,” as it allows for efficiency and safety through a microincision.
“It’s funny to think that our long search for a safer alternative to ultrasound ended up with ultrasound,” he said.
For Your Information:
- Alessandro Franchini, MD, can be reached at Istituto di Oculistica, Università di Firenze, Viale Morgagni 85, 50134 Firenze, Italy; 39-055-411765; fax: 39-055-4377749; e-mail: oculist@unifi.it or alessandrofranchini@yahoo.it. Dr. Franchini is a paid consultant for Advanced Medical Optics.
- Advanced Medical Optics can be reached at 1700 E. St. Andrews Place, Santa Ana, CA 92799; 800-449-3060; fax: 866-872-5635; Web site: www.amo-inc.com.
- Michela Cimberle is an OSN Correspondent based in Asolo, Italy.