Cold phaco heats up as new era dawns

Barbara Boughton in San Francisco

THE latest innovations in cold phaco systems offer new capabilities that allow surgeons to move up to the next step in cataract surgery-bi-manual micro-incision phaco, according to I. Howard Fine MD, who presented updated clinical results comparing six phaco systems at the annual conference of the ASCRS.
In a comparison study involving 200 eyes, the Millennium phacoburst system (Bausch & Lomb) produced 20/40 or better in 100% of patients at up to 24 hours following cataract surgery. The Sovereign WhiteStar™ (AMO) system produced 20/40 results in 94% of patients while the Legacy® NeoSonix (Alcon) had the same results in 96% of patients. The AMO Diplomax®, Staar Wave and Mentor (Paradigm) lagged behind with 81%, 79%, 54% of patients respectively achieving 20/40 or better post-op.

A previous study, comparing these technologies, was published the Journal of Cataract and Refractive Surgery in 2001 by Dr Fine and his colleagues. Neither the Millennium nor WhiteStar were available at the time of that study. Both promise improved technology and outcomes, and neither produced any oedema or striae during the 24 hours post-operative period.
The Millennium's phacoburst technology had an average phaco time of 3.10 seconds and 8.8% average power. The WhiteStar had an effective phaco time of 1.55 seconds and 1.8% average power.

"The microbursts of the new Millennium provide enhanced cavitational energy, which leads to fabulous results. The outcomes are dramatically better than with the Millennium pulse technology," Dr Fine said.
He acknowledged that the WhiteStar outcomes were also excellent, stressing that both the Millennium phacoburst and WhiteStar were capable of going to the next step in refractive surgery- bi-manual micro-incision phaco, which at present he is routinely using.

He compared results with the Millennium pulse technology versus the Millennium with burst mode software. With the pulse system, the effective phaco time for the Millennium was 5.4 seconds versus 3.1 seconds with phacoburst. The average phaco power was 13% with pulse technology, but only 8.8% with phacoburst. Ninety one percent of patients had clear corneas at 24 hours after surgery with the earlier system, while 100% had clear corneas with phacoburst.

Visual outcomes were also dramatically improved with the phacoburst technology. Ninety one percent of patients achieved 20/40 UCVA with the original system in the 24-hour follow-up period while 100% reached this level with the phacoburst. Moreover, 61% of patients in the phacoburst group achieved 20/25 UCVA in the immediate pre-operative period.

"You can get your control of burst length and rest length down to the millisecond range. The Sovereign also has great fluidics."
The Sovereign WhiteStar offers eight programmable duty cycles in which burst length and rest length are independently variable from 4 milliseconds in length up to 150 milliseconds.

The Millennium offers dual linear technology, which gives the surgeon the ability to control ultrasonics and aspiration simultaneously and independently. The new foot pedal has been refined and is now very user friendly, Dr Fine commented.
"With each increment of improvement in phaco technology, we improve outcomes, and we add new options for competitive refractive surgery procedures," he said.
Microphaco

Dr Olson predicts that with new technologies available on systems such as WhiteStar, cataract surgeons will soon be performing procedures with incisions as small as 1.0mm.
With continuous microphaco, wound burns are often a real possibility. However, with the WhiteStar system, this concern is allayed and safety is increased, commented Dr Olson in another presentation at the ASCRS conference.
In a previous study Dr Olson and colleagues reported that the maximum wound temperature reached 32.4 degrees C in cadaver eyes when occluded. For the experiment, the WhiteStar was set at CF (meaning one-third on and two-thirds off at 100% power for three minutes.

Another study by J Donnenfeld, (in press, Journal of Cataract and Refractive Surgery) found that maximum wound temperatures ranged from 24 degrees C to 36 degrees C in the eyes of 10 patients. However, another recent study showed that when tested in air, the Legacy remained cooler. As a result, Dr Olson decided to test the Legacy against the WhiteStar in a real world setting with two cadaver eyes, 18 hours post-mortem.
The researchers clamped the aspiration tube for 10 seconds to simulate occlusion. Temperature was measured within the wound using a microthermistor. With power at 50% and flow at 12 ml/minute, the WhiteStar achieved cooler temperatures more consistently. The Legacy, however, achieved higher temperatures overall but on multiple occasions dropped out as temperature rose. Similar results were achieved when WhiteStar and Legacy were tested for standard phaco with sleeve procedures and microphaco without sleeves.

Because the Legacy handpiece maintains stroke length, it decreases its energy output when not loaded, most dramatically in air. The WhiteStar at similar settings puts out more power) than the Legacy when tested in air, but it puts out less power in real world situations because it detracts its power not its stroke length, Dr Olson reported.
Olson noted that choosing irrigating choppers with technologies such as WhiteStar in microphaco is a vital decision. He prefers the MST Duet, which he said has a superior flow rate compared to other choppers he has tested.

Randall Olson
John A. Moran Eye Center, Salt Lake City, Utah, US
Randall.olson@hsc.utah.edu
I. Howard Fine
Eugene, Oregon, US
sherrie@finemd.com

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