ByErin L. Boyle

December 01, 2005

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Bimanual MICS improves with increased experience

Some surgeons claim microincision cataract surgery is an improvement over standard phaco. Others cite potential problems.

ByErin L. Boyle

While experience with microincision cataract surgery continues to grow around the world, there is still wide debate about its efficacy. Some surgeons say the procedure is a safer and more precise technique than standard phaco. They say MICS renders cataract surgery less invasive and less traumatic when performed properly. Other surgeons still express skepticism about the technique’s value, saying it offers no clear advantage while taking longer and requiring increased skill on the part of the surgeon.

I. Howard Fine

I. Howard Fine, MD, who is perhaps the leading exponent of MICS in the United States, asserts that MICS has better fluidics than coaxial phaco because it is a step closer to the ideal in cataract surgery — a completely closed system.

Dr. Fine, speaking at the American Society of Cataract and Refractive Surgery meeting in Washington, said two smaller incisions offer many benefits over the standard, one-incision phaco technique.

“We have improved followability, we can use the irrigating stream of fluid as a manipulator to bring the material to the phaco tip, and we think we have more stable chambers,” Dr. Fine stated. “We think it’s the safest, least invasive lens technique for refractive lens exchange.”

Endothelial cell loss

A common concern regarding MICS has been the loss of endothelial cells following the procedure, according to George Beiko, MD, FRCS. After using MICS with good results for more than 2 years, he said he wanted to perform a study to counter reports of up to 50% cell loss with the procedure. His study examined two groups – patients undergoing standard phaco or bimanual MICS.

“As we know, there is a natural endothelial cell loss, with a decrease of about 0.3% to 0.5% cells per year, and our surgery certainly influences this in that there is loss at the time of cataract surgery,” Dr. Beiko said.

The study found that both groups had nearly identical endothelial cell loss of about 12.4%, he said.

“At the very least, we are getting the same amount of cell loss with MICS as we are with conventional phaco. And this study also highlights that you have to audit your procedure on a periodic basis,” he said.

In the 30-patient study he used the Advanced Medical Optics Sovereign phacoemulsifier with WhiteStar technology. Dr. Beiko performed nucleus removal at the iris plane. The balanced salt solution had no additives. At the end of the case, intracameral cefuroxime and dexamethasone were injected into the eye.

“When looking at endothelial cell loss, we have to look at how we measure it. We know the measurements are reproducible when done with one instrument, but numbers are not interchangeable,” he said.

In a separate study of 100 patients, Rita Mencucci, MD, also recently found no statistically significant difference between standard phaco and bimanual phaco regarding endothelial cell loss.

Dr. Mencucci cited many factors that can damage endothelium in both phaco procedures, including corneal distortion, nuclear fragmentation, IOL contact and release of free radicals. For the MICS procedure, there is another issue as well: the surgeon’s inexperience with the new technique, she said.

“In MICS, there might also be present a learning curve, a longer surgical time at the beginning,” Dr. Mencucci said. Despite this, she said, her study found no difference in endothelial cell loss between the two procedures.

Note of caution

Some surgeons advise caution before fully embracing MICS. Reasons to be cautious include the fact that MICS can cause leakage and increase the risk of infection from multiple incisions, said Robert H. Osher, MD.

Dr. Osher said he investigated the MICS technique for 2 years. After extensive research, he switched back to a coaxial phaco technique. In an interview with Ocular Surgery News, Dr. Osher said he found that MICS “had significant drawbacks without significant advantages.” Drawbacks include a higher level of surgical skill required, less efficiency because of lower vacuum and aspiration rates with lower infusion through the smaller tip, and longer surgery time.

He said he found the primary drawback to be that patients’ corneas do not look as clear on day 1 postop as he has seen with standard coaxial phaco in studies he has previously published regarding early, uncorrected vision. The incisions were also not as watertight as he would have expected for coaxial phaco, he said.

“As a result, I started another project entirely, and that is to keep the same theoretical advantages of a smaller incision, which we know is inevitable in ophthalmology, even though there is not a smaller IOL available in the United States,” Dr. Osher said. “We know there will be one, but again, we can’t make an unwise movement forward and say we’re going to make a smaller incision and sacrifice all the IOL advantages which we currently have.”

Hydrochop for MICS

Other surgeons are also working to find appropriate techniques to safely perform MICS. Hideharu Fukasaku, MD, said he has devised a chopping instrument that uses water to split open the nucleus. The “hydrochopper” makes MICS easier and faster in nuclei of any degree of hardness, he said.

Hideharu Fukasaku, MD [photo]
Hideharu Fukasaku

Dr. Fukasaku said the hydrochopper has two distally placed ports that allow water jets to be generated deep within the cataractous nucleus. The chopper is first pushed into the lens to split it and then pushed again into each of the halves, ultimately forming four quadrants that can easily be emulsified using phaco power.

He said the technique has a number of advantages over other MICS techniques. It is difficult to divide a hard nucleus with a bulky irrigating chopper, he said. The hydrochopping technique makes MICS much easier, safer and faster, especially in hard nuclei, he said.

“The surgeon can always see the instruments,” Dr. Fukasaku said. “Blind maneuvering behind the iris is not necessary with the hydrochop technique.”

Performing MICS

At this year’s ASCRS meeting, Dr. Fine detailed how he performs MICS.

He said he creates two incisions, one on the left that is slightly horizontal and one on the right that is slightly vertical, so he can coordinate the two instruments more comfortably.

After creating the incisions, he performs cortical cleaving hydrodissection and then hydro-expresses the lens out of the bag. The irrigator is held on top of the lens, and a steady stream of irrigation is directed into the eye. He said there is no chance of abrading the corneal endothelium with the nucleus because it is remote from the endothelium, separated by the irrigator.

He carousels the lens in the plane of the capsulorrhexis, equidistant from both the corneal endothelium and the posterior capsule. He performs this maneuver with zero ultrasound, using fluidics alone. Then the phaco tip is tilted back into the bag and the entire cortical envelope jumps out of the capsule.

MICS with WhiteStar

According to Richard B. Packard, MD, FRCS, FRCOphth, AMO’s WhiteStar technology has changed the way surgeons think about phaco power and has influenced virtually every other manufacturer of phaco machines to change the way they deliver power. That change assists in the performance of the MICS procedure, he said.

Richard B. Packard, MD, FRCS, FRCOphth [photo]
Richard B. Packard

“What it did was give us micropulse as a phaco energy,” he said. “Bursting and resting means that you get a decrease in buildup of heat at the tip, and also reduced pulse forces.”

John R. Kearney, MD, described his technique using the WhiteStar technology with a phaco-flip technique and the ultimate soft-shell viscoelastic technique. In the soft-shell technique, Healon5 (sodium hyaluronate, Advanced Medical Optics) and balanced salt solution are used together in a sealed or closed system, Dr. Kearney said. He said the Healon5 protects the cornea and the use of the two different viscosity materials allows precise control through 1.1-mm incisions.

Dr. Kearney said he used an aspiration rate of 26 cc/minute when the nucleus was not occluding the phaco tip. He said he wanted a low flow when the tip was not occluded, but more steady suction when occluded. He said the threshold was set at 35 so that there was not too much suction when the rise occurred. The maximum vacuum was set at 400 mm Hg.

A long pulse was used to create a hole in the nucleus, at 4 pulses per second, Dr. Kearney said. The phaco flip in the safe zone was controlled and efficient, he said.

Wound temperature

Rosa Braga-Mele, MD, FRCSC [photo]
Rosa Braga-Mele

Rosa Braga-Mele, MD, FRCSC, conducted a study using MICS with advanced power modulation technology, evaluating wound temperature with the Bausch & Lomb Millennium phacoemulsifier. She said she found no significant temperature rises.

“The newer power modulations are safe and effective for MICS, and there’s a flexibility of programs to fit your needs,” she said.

She examined the wound temperature associated with the advanced power modulations in an in vitro setting in porcine eyes. The operation was conducted with two clear corneal incisions of 1.4-mm width, to fit the Microflow needle and a 20-gauge irrigation cannula. A modified sleeve was used to secure a thermocouple to the exposed phaco needle 2 mm behind the tip.

“You’re measuring the temperature of the actual phaco needle because, if you were just measuring the wound temperature, there’s a lot of fluid around that wound, so you might be cooling it,” she said.

The Millennium showed no significant temperature rise in these initial studies and no trauma or wound burns in the clear corneas on day 1, Dr. Braga-Mele said. The new custom-control software with the Millennium now has programmable linear power, she said.

“What I like about the new fixed burst mode is that it’s variable duty cycle pulse without thinking about it. So I can put it on 4 msec on, 4 msec off, which is essentially 125 pulses/second; or 6 msec on, 18 msec off, which is essentially 75 pulses/second with a 30% duty cycle. It’s less thinking for me and so easier for me to do,” Dr. Braga-Mele said.

For Your Information:

George Beiko, MD, FRCS, can be reached at 180 Vine St., Suite 103, St. Catharine’s, ON L2R 7P3 Canada; +1-905-687-8322; fax: +1-905-687-8766; e-mail: george.beiko@sympatico.ca.

Rosa Braga-Mele, MD, FRCSC, can be reached at 245 Danforth Ave., Suite 200, Toronto, Canada M4K 1S2; +1-416-462-0393; fax: +1-416-462-3612; e-mail rbragamele@rogers.com.

I. Howard Fine, MD, is a clinical professor of ophthalmology at the Casey Eye Institute at Oregon Health & Science University in Portland and in clinical practice with Drs. Fine, Hoffman & Packer, LLC. He can be reached at 1550 Oak St., Suite 5, Eugene, OR 97401 U.S.A.; +1-541-687-2110; fax: +1-541-484-3883; e-mail: hfine@finemd.com; Web site: www.finemd.com.

Hideharu Fukasaku, MD, can be reached at Yokohama S.T. Building 1-11-15 Kitasaiwai, Nishi-ku Yokohama, Japan 220-0004; +81-45-3250055; fax: +81-45-325-0054; e-mail: h-f-eye@po.lijnet.or.jp.

John R. Kearney, MD, can be reached at 135 County Highway 128, Johnstown, NY 12095 U.S.A.; +1-518-762-2020.

Rita Mencucci, MD, can be reached at Università degli Studi di Firenze, Clinica Oculistica II, Viale Morgagni 85, 50134 Firenze, Italy; +39-055-411-765; fax: +39-055-437-7749; e-mail: rita.mencucci@unifi.it.

Robert H. Osher, MD, can be reached at the Cincinnati Eye Institute, 10494 Montgomery Road, Cincinnati, OH 45242 U.S.A.; +1-513-984-5133; fax: +1-513-936-4881; e-mail: rhosher@cincinnatieye.com.

Richard B. Packard, MD, FRCS, FRCOphth, can be reached at The Prince Charles Eye Unit, King Edward VII Hospital, St. Leonards Road, Windsor, Berkshire SL4 3DP, United Kingdom; +44-1753-860441; fax: +44-1753-636487; e-mail: eyequack@vossnet.co.uk.

Erin L. Boyle is an OSN Staff Writer who covers all aspects of ophthalmology.