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Brunescent lenses removed safely, effectively with cold phaco
System reduces amount of energy in the eye, trauma-producing turbulence is also lessened
Ophthalmology Times

Philadelphia-The Sovereign WhiteStar system is a revolutionary "cold" phaco technology that is unique in its ability to emulsify the most brunescent nuclei without any risk of a wound burn, according to David F. Chang, MD, who reported on his experience with WhiteStar (AMO, Irvine, CA) here at the annual meeting of the American Society of Cataract and Refractive Surgery.

"Cold phaco is a prominent topic this year, because in the United States, we can now purchase at least three different 'cold' phaco systems. In addition to WhiteStar, both laser phaco and sonics (Staar Surgical) are pure cold phaco systems that allow us to remove the lens without any significant heating of the phaco tip," said Dr. Chang, clinical pro-fessor of ophthalmology at the University of California, San Francisco and is in private practice in Los Altos, CA.

"The promise of cold phaco has always been twofold. First, we would like to improve safety, by eliminating the risk of a wound burn and by decreasing the amount of energy introduced, which, in turn, might lessen endothelial trauma," he said. "Second, bimanual phaco would become possible if the coaxial irrigation sleeve were no longer needed to cool the phaco tip," Dr. Chang explained. He has performed more than 700 cases using the WhiteStar system.

However, Dr. Chang asserts that we should use brunescent nuclei as the true test of the benefits of any new phaco technology.

"These cataracts challenge us with a poor red reflex and a greater risk of wound burn, endothelial cell loss, and posterior capsule rupture," he said. "Therefore, these are the cases where we want to have any additional help that new technology can give us. This is why it has been disappointing that neither laser phaco nor sonics is effective for re-moving denser lenses."

WhiteStar can handle the brunescent lens because it still delivers full-power ultrasound. Clinically significant heat is prevented by a new paradigm of pulse mode. Dr. Chang calls this "hyperpulse" because the pulse rates are on the order of ten times more than those traditionally used. In addition, the ratio of the phaco "off" versus the phaco "on" duration can be set at 4:1, compared with traditional pulse, which is 1:1. In other words, the pause between pulses is four times as long as the individual pulses.

"It is this dramatic increase in the frequency and duration of the rest periods that keeps the tip cool," Dr. Chang explained. "This has led to overall reduction in average equivalent phaco time (EPT) compared with non-WhiteStar cases using the same technique, machine, and settings.

"An unanticipated benefit of hyperpulse is a dramatic increase in nuclear followability," Dr. Chang reported. "This is particularly obvious with brunescent lenses, where there is typically excessive chatter and turbulence. This is because rigid fragments cannot mold into the mouth of the phaco tip and are kicked away by the increased stroke lengths that define higher phaco power.

"This increased turbulence of nuclear particles may be a significant factor in the greater endothelial cell loss that occurs with brunescent lenses," Dr. Chang concluded.

Because the ultrasound is interrupted so frequently with WhiteStar, the overall repelling force of the vibrating phaco tip is drastically reduced, which allows the vacuum to hold material at the tip better. "This decrease in chatter and turbulence is probably much safer for the endothelium in these challenging cases," Dr. Chang noted.

Dr. Chang presented a consecutive series of the first thirty brunescent 4+ lenses he removed using the WhiteStar system.

"The range in EPT was from 6 to 30 seconds. The average EPT for the 30 lenses was 9.1 seconds, using a vertical phaco chop technique with no sculpting," he reported. "The primary clinical difference in these brunescent lenses was clearer corneas immediately postoperatively than I was accustomed to, using the same Sovereign handpiece and fluidics without WhiteStar. I attribute this to the very obvious improvement in followability with WhiteStar."

Dr. Chang noted that while bimanual phaco may be of limited value until paracentesis-injectable IOLs are developed, WhiteStar offers important advantages for conventional phaco.

"Besides reducing the EPT, and eliminating the risk of wound burn, the reduction in particulate turbulence with dense nuclei is safer for the endothelium," Dr. Chang concluded. After so much research has gone into alternatives to ultrasound energy, he suggested that it is ironic that hyperpulse ultrasound seems to be the best "cold" technology yet.

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