Microburst mode offers advantages in phaco chop technique
With the Alcon Infiniti, phaco time and phaco power were lower in microburst mode than in burst/pulse mode.
The Alcon Infiniti Vision System has many advantages over its predecessor, the AdvanTec Legacy console, one of which is microburst technology. Using microburst, a surgeon can efficiently and rapidly defragment and remove the nucleus. I perform a chopping technique for all of my cataract surgeries. By not creating a groove before chopping (as is done with the stop-and-chop technique), I use less phaco power in the eye (Figure 1). It is accordingly more essential that the burst mode work well to embed the phaco tip in the nucleus for the first chop (Figure 2).
Like many surgeons who perform a pure chopping technique, I used to switch to a pulse mode for quadrant removal after chopping the nucleus into quadrants. With the Infiniti, the burst duration can be decreased to 5 ms bursts, as opposed to 30 ms on the AdvanTec Legacy. In terms of phaco-on time, the AdvanTec Legacy is preset at 50% on and 50% off. With the Infiniti, both the on and off times in the burst mode can be independently adjusted from 5 ms to 500 ms. I noticed that if I did not switch from burst to pulse mode, quadrant removal occurred more rapidly in many cases. Although the pulse mode was safe for quadrant removal, I was retaining good control of the nucleus with a pure burst setting using microburst durations.
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Images: Pandit RT
I decided to investigate which method of ultrasound use would be most efficient. I performed phacoemulsification with posterior chamber IOL implantation on sequential patients with 2+ to 3+ nuclear sclerotic cataracts and no other anterior chamber abnormalities. In all patients, a 1.1 mm flare tip with a vertical chopping technique was performed. After breaking the nucleus into halves (Figure 3), two additional chops were performed to divide the nucleus into four quadrants (Figure 4). For all patients, ultrasound power in burst mode was set at a maximum of 60% with linear control, vacuum at 525 mm Hg (fixed) and aspiration flow rate of 50 (fixed) with a dynamic rise of 1. For the first 10 patients, dubbed the burst/pulse group, I initiated phaco chop with a burst setting (20 ms on, 40 ms off) and followed in pulse mode (40 pulses per second at 65% on time) for quadrant removal. For the next set of 10 patients, I performed chopping and quadrant removal using burst mode only (20 ms on, 40 ms off). This was called the burst-only group.
I compared total phaco time, phaco power and effective phaco time in the two groups. The results can be seen in Table 1. These data suggest that the burst-only method results in more efficient surgery, confirming my subjective impression during surgery. The average phaco power was similar between the two groups, but the time spent in phaco mode was less for the burst-only group, and the effective phaco power used was also less. Both groups had similar postoperative outcomes.
Next I evaluated different combinations of on and off time in burst mode. In my chopping technique, I found that 5 ms of on time was too short to adequately embed into the nucleus and retain the initial purchase for effective vertical chopping. On the other hand, an on time of greater than 20 ms seemed excessive and unnecessary. I collected data on 20 additional patients with 2+ to 3+ nuclear sclerotic cataracts undergoing surgery with burst-only phaco chop. For the first 10 patients, I used an on time of 10 ms and an off time of 20 ms (10/20 group), and for the next 10 patients I used an on time of 10 ms and an off time of 30 ms (10/30 group). The results can be seen in Table 2. As these data would suggest, there was not a great difference between phaco energy used in the different combinations of on and off time in burst mode. Intraoperatively, however, I felt more comfortable and in better control of quadrant removal with the 10/30 group. Overall, I felt quadrant removal with both of these groups proceeded more rapidly than with the initial burst-only group using 20 ms on and 40 ms off.
At this time, I prefer to use burst-only at settings of 10 ms on and 30 ms off for my entire nuclear removal, from initial embedding up to final quadrant removal. Burst mode offers excellent nuclear defragmentation with similar control as pulse mode, while at the same time decreasing the total amount of phaco energy used. The theoretic advantage of hyperpulse (ie, less chatter of nuclear fragments and more flow toward the phaco tip) was not apparent to me when compared with the microburst settings above, which also resulted in minimal chatter and excellent followability of fragment removal. Efficiency was also improved by avoiding the extra step of changing from a burst to pulse setting when beginning quadrant removal. And finally, by staying in one mode during the entire nuclear removal, it was easier and quicker to switch between chopping and quadrant removal. In some cases, I prefer to debulk the nucleus by removing the first two quadrants before chopping the remaining half of the nucleus. One can change easily between chopping and quadrant removal as many times as needed on any individual case without having to change any settings.
For more information:
- Rahul T. Pandit, MD, is a clinical assistant professor of ophthalmology at Baylor College of Medicine. He can be reached at Medical Center Ophthalmology, 6624 Fannin St., Suite 2100, Houston, TX 77030; 713-796-0120; fax: 713-796-0897; e-mail: email@example.com; Web site: www.houstoneyemd.com. Dr. Pandit has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Alcon can be reached at 6201 South Freeway, Fort Worth, TX 76134; 817-293-0450; fax: 817-568-6142; Web site: www.alconlabs.com.