Ultrasonic power reduction during phacoemulsification using adjunctive NeoSoniX technology

Ultrasonic power reduction during phacoemulsification using adjunctive NeoSoniX technology James A. Davison, MD Purpose: To compare the phacoemulsification times and powers used in 3 phacoemulsification machine configurations. Setting: Wolfe Eye Clinic, Marshalltown, Iowa, USA. Methods: A randomized prospective study of 410 consecutive cases was conducted. All cases were performed using the Alcon Legacy 20000 phacoemulsification machine. Configurations were the Standard Legacy 20000 machine (n Z 165), Advantec upgraded Legacy 20000 (n Z 112), and Advantec upgraded Legacy 20000 with NeoSoniX (n Z 133). Preoperative measurements included the patient’s age and cataract grade using the nuclear color (NC) scale of the Lens Opacities Classification System III (LOCS III). Intraoperative measurements included machine-measured phacoemulsification time and average percentage of maximum power expenditure. An independent statistician performed analysis of covariance on NC for each of the machine configurations. Results: The mean age in years and the NC value were similar in each group. There was no significant difference in phacoemulsification time in minutes among the 3 machines: Standard Z 1.17, Advantec Z 1.12, NeoSoniX Z 1.16. The average percentage of maximum power consumption was similar for Standard Legacy 20000 at 38.00% and Advantec Legacy 20000 at 37.97% but significantly less for Advantec Legacy 20000 with NeoSoniX at 27.56% (P!.001). With the NeoSoniX-incorporated machine, compared with Standard and Advantec, a 27.5% reduction in ultrasonic energy power expenditure was observed all grades of nuclear density. Conclusions: The addition of 15% amplitude NeoSoniX rotational energy reduced total ultrasonic power expenditure by 27.5% for all cataract nuclear densities. J Cataract Refract Surg 2005; 31:1015–1019 ª 2005 ASCRS and ESCRS

ince the advent of phacoemulsification,1 it has been recognized that ultrasonic energy can have deleterious effects on ocular structures, particularly the corneal endothelium.2–11 Concern increases when considering continuing cell loss demonstrated in several long-term

S

Accepted for publication July 20, 2004. Reprint requests to James A. Davison, MD, Wolfe Clinic, PC, 309 East Church Street, Marshalltown, Iowa 50158, USA. E-mail: jdavison@ wolfeclinic.com. ª 2005 ASCRS and ESCRS Published by Elsevier Inc.

studies.12,13 Various devices14–21 (Kelman phacoemulsification tip, personal communication, Alcon Surgical, August 2001) and surgical strategies (K. Nagahara, ‘‘Phaco chop,’’ film presented at the 3rd American– International Congress on IOL and Refractive Surgery, Seattle, Washington, USA, May 1993; K. Nagahara, MD, ‘‘Phaco-chop Technique Eliminates Central Sculpting and Allows Faster, Safer Phaco,’’ Ocular Surgery News, International Edition, October 10, 1993, pages 12–13)22–33 have been derived to reduce the amount of ultrasonic energy used during phacoemulsification. 0886-3350/05/$-see front matter doi:10.1016/j.jcrs.2004.09.025

ULTRASONIC POWER REDUCTION DURING PHACOEMULSIFICATION

In 2001, Alcon Surgical incorporated its Advantec NeoSoniX technologies into the Legacy 20000 phacoemulsification machine. The Advantec portion is a hardware and software upgrade of the machine, which incorporated improvements to increase operating efficiency (personal communication, Alcon Surgical, August 2001). This upgrade was required to utilize the NeoSoniX technology. NeoSoniX is a hardware software option, which includes a dedicated handpiece that produces rotary oscillations of the phacoemulsification tip of up to 2 degrees on both sides from neutral (measured as a percentage of maximum rotational amplitude) at 100 cycles per second (personal communication, Alcon Surgical, August 2001) (Figure 1). This oscillatory motion can be used alone or as an adjunct to ultrasonic energy. This oscillation effect has been suggested to reduce the amount of phacoemulsification energy required to remove the typical human cataractous nucleus.34 We examined whether the Advantec upgrade alone or the Advantec with NeoSoniX machine and handpiece configuration could produce a reduction in machine-measured phacoemulsification time and average power expenditure over a wide range of cataract densities as categorized within the Lens Opacities Classification System III (LOCS III).35

Materials and Methods A prospective randomized schedule was used to operate on patients with 1 of 3 Alcon Legacy 20000 machine configurations: standard Legacy 20000 (Standard), Advantec-upgraded Legacy 20000 (Advantec), and Advantecupgraded Legacy 20000 with NeoSoniX (NeoSoniX). Surgeries were carried out from June 29, 2001, through November 2, 2001. Patients had surgery and were recorded in consecutive fashion on each day of surgery. Two rooms in 1 location were used with 1 of the 3 machine configurations in each room. Rooms were alternated back and forth with the machine configuration set up in each room used the whole day. There was some variation in the availability of the Table 1.

Figure 1. The NeoSoniX handpiece features traditional longitudinal ultrasonic vibration amplitudes with a component of 6 2 degrees and 100 rotary oscillations per minute generated by an electric motor.

machines, which produced an imbalance in the total number of patients having surgery with each. The final number of patients were Standard, n Z 165; Advantec, n Z 112; and NeoSoniX, n Z 133. All cataracts were graded preoperatively at the slitlamp by the investigator (J.D.) according to the LOCS III.35 It has been shown previously that there is a correlation between phacoemulsification time and nuclear color (NC) scale values (ie, the amount of yellow brown color of the nucleus).36 Final intraoperative data correlations of this current study were similarly accomplished using the NC scale. All patients had surgery by 1 surgeon (J.D.) using a 2 groove–4 quadrant in situ fracture (divide and conquer) method, which included lidocaine 1% topical–intracameral anesthesia, temporal clear corneal incision, and Provisc (1% sodium hyaluronate) for capsulorhexis and intraocular lens (IOL) insertion, and straight 0.9 mm 45 degree ABS MicroFlare tip.17 Viscoat was (sodium hyaluronate 3%– sodium chondroitin 4%) employed during quadrant removal in patients with nuclei graded NC 4.0 or higher. With the exception of 15% NeoSoniX energy, all parameters including balanced salt solution (BSS) bottle height of 78 cm, maximum available amount of ultrasonic energy, maximum available vacuum, and aspiration flow rate were the same for each group (Table 1). Intraoperative data collected included machine-measured phacoemulsification time and machine-measured mean power used for each patient. For both machine-measured

Alcon Legacy 20000 phacoemulsification machine parameters.

Technique

Tip

In situ fracture 45  0.9 mm flare ABS

Step Groove

Power Mode

Power NeoSoniX Activation NeoSoniX Vacuum AFR Max (%) Threshold (%) Maximum (%) mm Hg cc/min

Continuous

90

0

15

50

14

Quadrant removal Continuous

70

0

15

500

35

ABS Z Aspiration Bypass System; AFR Z aspiration flow rate

1016

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phacoemulsification time and average percentage power expenditure, the dependent variable (ie, machine-measured phacoemulsification time or average percentage power expenditure) on NC was regressed, allowing for intercepts and slopes particular to the machine configuration. If there was no evidence of a difference among the slopes of the 3 machine configurations, a common slope was modeled for the 3 machines. If the common slope was not significantly different from zero, the covariate (NC) was dropped from the model and thus analysis of variance was used to test for differences among the machine configurations.

Table 2.

Mean phaco time and maximum power.

Parameter/Method

Estimate

SD

Standard

1.17

0.04

Advantec

1.12

0.05

AdvantecCNeoSoniX

1.16

0.03

Standard

38.00

0.87

Advantec

37.97

1.17

AdvantecCNeoSoniX

27.56

0.76

Phaco time (min)

Maximum power (%)

Results There was no significant difference in mean phacoemulsification time measured in minutes among the 3 machines: Standard Z 1.17, Advantec Z 1.12, NeoSoniX Z 1.16. The mean percentage power expenditure was similar for Standard Legacy 20000 at 38.00 and Advantec Legacy 20000 at 37.97, but NeoSoniX Legacy 20000 at 27.56 was significantly less than Standard and Advantec (P!.001) (Table 2). Even though there was a reduction in mean power expenditure for the NeoSoniX machine, there was no evidence of a significant difference in the slopes of plotted linear regressions of NC versus average power percentage among any of the 3 machine configurations. The common slope of NC (6 standard deviation) for the 3 machine configurations was 8.19 6 1.04 (ie, when NC increased by 1 unit, the average percentage power expenditure increased by 8.19 units for each of the 3 machine configurations) (Figure 2). Thus, when comparing the NeoSoniX-incorporated machine to the Standard-

equipped or Advantec-equipped Legacy 20000, there was a 27.5% reduction in ultrasonic energy power expenditure across all grades of nuclear density within the LOCS III system.

Discussion The mean range of the change in corneal endothelial cell density (ECD) losses after contemporary cataract surgery is to be reported between 1% and 23%.37 It has been demonstrated that increased phacoemulsification energy expenditure is associated with increased corneal ECD loss.11,28,31,38–40 Because of this, techniques and technology have evolved together with the intent to use less ultrasonic energy during phacoemulsification. Ultrasonic energy reductions have been achieved in 4 ways: (1) tip design17–19,21 (Kelman phacoemulsification tip, personal

Figure 2. Linear regression of average power percentage against LOCS III NC value for each of the 3 Legacy 20000 machine configurations.

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communication, Alcon Surgical, August 2001); (2) restricting energy into fractions of second pulses or bursts (Alcon Legacy 20000)33,41 and millisecond-level microbursts (AMO Sovereign)38 (Alcon Infinity); (3) using nonultrasonic energies such as sonic frequencies (Starr Surgical)42 and NeoSoniX-generated tip rotations (Alcon Legacy 20000, Alcon Infinity); and (4) pulsed water jet technology (Aqualase, Alcon Infinity). All of these technologies use a small incision to achieve lower ECD losses as an alternative to the large-incision-planned extracapsular cataract extraction, which uses no ultrasonic energy but is associated with a 12% decrease in ECD after surgery.43 This study demonstrates that the addition of a very small amount of adjunctive NeoSoniX rotational oscillation, as applied to 45 degree 0.9 mm straight phacoemulsification tips, substantially reduces the amount of machine-measured mean percentage phacoemulsification power expenditure and thus total ultrasonic energy exposure over all densities of nuclear hardness. Further studies are needed to prove the effectiveness of, and derive optimal rotational amplitudes for, different tip configurations as applied to different grades of cataract within the various stages of the phacoemulsification process. More important, studies are needed to correlate any changes in corneal ECD associated with its use.

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