Hyperpulse mode found more efficient for hard nuclei

San Francisco-The hyperpulse mode of the Millennium Microsurgical System (Bausch & Lomb) more efficiently breaks up hard nuclei with a shorter average absolute phacoemulsification time than the pulse mode, with less postoperative corneal edema, Chee-Chew Yip, MMed, FRCS, reported at the American Society of Cataract and Refractive Surgery annual meeting.

"Advanced phacoemulsification is a very efficient procedure and minimizes the heat that is generated to decrease damage to the intraocular structures," Dr. Yip explained. He is a consultant, department of ophthalmology, Alexandra Hospital and Tan Tock Seng Hospital, Singapore. "Therefore, most phaco systems tend to use high vacuum and lower phaco time and power. The power is one modification that uses ultrasound energy in a continuous pulse mode. The hyperpulse is a newer modification in the Custom Control Software that delivers the energy in much more frequent pulses in a much lower duty cycle, which refers to the percentage of time that phaco energy is on in each power cycle."

Dr. Yip and colleagues evaluated the efficiency and safety of the pulse and hyperpulse mode in the Millennium Microsurgical System.

"It is interesting to note that for the hyperpulse mode a much higher pulse-i.e., 65 pulses per second compared with 10 pulses in the pulse mode-and a much lower duty cycle-i.e., 35% compared with 50%, respectively-are used," he said.

One hundred ninety-three eyes were included in the study; 84 eyes underwent cataract surgery using the pulse mode and 109 eyes using the hyperpulse mode.

Preoperatively, the investigators measured the IOP and best-corrected visual acuity, and graded the cataracts based on the degree of nuclear sclerosis. The cataracts were divided into soft and hard cataracts, with hard defined as nuclear sclerosis of 3+ or greater. Intraoperatively, the investigators measured the average phaco power, the elapsed phaco time, and the absolute phaco time, which is the time when the power is on 100%. At postoperative day 1, they measured the best-corrected visual acuity and determined the presence of postoperative corneal edema.

Dr. Yip reported that the two groups were comparable in age, sex, race, and lens density.

"For the group of patients with soft cataracts (n = 84), there was no difference between the pulse group and the hyperpulse group in the average phaco power and the absolute phaco power (10.5 ± 3.0% and 6.6 ± 3.2 seconds, respectively, and 11.7 ± 4.1% and 6.5 ± 4.3 seconds, respectively) (p = 0.068 and p = 0.981, respectively). However, for the patients with hard cataracts (n = 109), the absolute phaco time was much shorter in the group of patients treated using the hyperpulse mode compared with those treated using the pulse mode (11.7 ± 5.0 seconds compared with 15.4 ± 7.4 seconds, respectively) (p = 0.007). However, the mean phaco power used in the hyperpulse group was slightly higher than in the pulse group (16.6 ± 3.0% versus 14.9 ± 3.3%, p = 0.026)," Dr. Yip reported.

Regarding the best-corrected LogMAR visual acuity postoperatively, the groups with soft cataracts had improvement and the results on the first postoperative day were similar for both groups. The patients with hard cataracts had better LogMAR visual acuity postoperatively (p = 0.036) if they were treated using the hyperpulse mode compared with the pulse mode.