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DISCUSSION 1

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The discussions featured in this supplement to Retina Today are based on panel discussions held during the 2008 American Academy of Ophthalmology meeting in Atlanta.

David S. Boyer, MD, is a Clinical Professor of Ophthalmology at the University of Southern California Keck School of Medicine, Department of Ophthalmology in Los Angeles. Dr. Boyer is a member of the Retina Today Editorial Board.
Timothy G. Murray, MD, MBA, FACS, is Professor of Ophthalmology and Radiation Oncology at the Bascom Palmer Eye Institute, University of Miami Miller School of Medicine.
Stanislao Rizzo, MD, is at the Eye Surgery Clinic, Santa Chiara Hospital, in Pisa, Italy. Dr. Rizzo is a member of the Retina Today Editorial Board.
Pravin U. Dugel, MD, is Managing Partner of Retinal Consultants of Arizona and Founding Member of the Spectra Eye Institute in Sun City, AZ. Dr. Dugel is a member of the
Retina Today Editorial Board.
Peter K. Kaiser, MD, is in the Vitreoretinal Department at the Cole Eye Institute, Cleveland Clinic. Dr. Kaiser is a member of the Retina Today Editorial Board.

David S. Boyer, MD: Key features of the CONSTELLATION Vision System (Alcon Laboratories, Inc., Fort Worth, TX) that distinguish this system from other technology for vitreoretinal surgical procedures include high-speed cut rate and duty cycle control. How do these features translate to practice?

Stanislao Rizzo, MD: High cutting speed is important for safety because it should translate to less traction on the retina. Duty cycle is important because it allows me a new variable to control flow.

Timothy G. Murray, MD, MBA, FACS: For highervolume vitreoretinal surgeons, the CONSTELLATION system is revolutionary. For the first time in my experience, technology is not an impediment in surgery. I prefer to cut at high rates, taking small pieces of tissue and minimizing the translational forces on the peripheral tissue. The limitation with previous technology is primarily the inability to maintain good flow at high cut rates. In core vitrectomy, I will use an openbias cutter operating at 5000 cpm, and I can now switch to a closed duty cycle and shave tissue off the retinal surface with no movement to the detached or attached retina. So, for the first time, we are able to maintain 5000 cpm with the ability to have the flow characteristics for both core vitrectomy and those consistent with detached retina manipulation.

Dr. Boyer: Dr. Dugel, can you explain duty cycle control and its importance to complication prevention?

Pravin U. Dugel, MD: Duty cycle is an important parameter, albeit a newer concept to retina surgeons. By definition, duty cycle is the percentage of time that the cutter is open compared to the overall cut cycle time. Although there are specific percentages that can be assigned to the duty cycle, we usually refer to three: closed bias, open bias, and 50/50. In closed bias, the cutter mouth is closed most of the time and flow is reduced; in open bias, it is open and flow is increased. In 50/50, as one would assume, the amount of open-time and closed-time is equal and flow is moderate.

Duty cycle allows the surgeon to change flow without changing cut rate or vacuum, which is a significant improvement over the spring technology we have been using. As cutting rates were increasing, the limits of the spring-loaded cutter were maximized and the port was unable to stay open long enough for such fast cut rates. For example, with the ACCURUS (Alcon Laboratories, Inc.) at 2500 cpm, the port is only open approximately 30% to 40% of the cutting time. The new design of the ULTRAVIT cutter contains no springs, so there are two separate air lines, which means that duty cycle is completely in the control of the surgeon. One can cut at 5000 cpm and keep an open-bias duty cycle, eliminating the problem of decreasing flow.

Finally, duty cycle allows for excellent followability when dealing with fibrous tissue or retained lens material.

Dr. Boyer: When converting from 20-gauge vitrectomy to 23- or 25-gauge surgery, are there cases you would avoid?

Dr. Rizzo: I might avoid cases of macular pucker because the vitreous can be unpredictable.

Dr. Dugel: I have performed 23-gauge surgery for 2 years, and would not avoid any cases with this technology. In fact, I would propose that it is the hardest cases in where the features on the CONSTELLATION become most useful. For example, a combined traction and rhegmatogenous retinal detachment can begin with a core-mode setting at 4000 cpm to 5000 cpm, and open-bias duty cycle, and vacuum of 400 mm Hg to 500 mm Hg. The detached retina can then be addressed in shave mode, keeping the cut speed at 5000 cpm, with an open duty cycle to reduce the flow. After shave mode is complete, the cut rate can be decreased to 3000 cpm, and the duty cycle can be adjusted to open-bias, allowing the surgeon to address the fibrous tissue.

The cutter on the CONSTELLATION is specifically designed for small-gauge surgery, as opposed to previous technology that basically took large-gauge instrumentation and shrunk it down to fit, using the same basis for fluidics.

On the CONSTELLATION, the cutter is not just a cutter anymore. Port optimization, which moves the port closer to the tip of the probe enables me to have better flow control with duty cycle, but also makes the cutter a multifunctional tool, reducing my need for horizontal and vertical scissors.

Peter K. Kaiser, MD: The CONSTELLATION Vision System also offers the ability to micropulse and proportionately control reflux. The cassette on the CONSTELLATION allows an increase of fluid that is proportional to the circumstances. For example, if you are operating on a patient with diabetes who begins to bleed, you can switch to proportional reflux mode and the fluid will increase to the extent where it effectively pushes the blood out of the way.

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