- Email: [email protected]
Comparative clinical trial of ultrasound phacoemulsification with and without the WhiteStar system
J CATARACT REFRACT SURG - VOL 32, JANUARY 2006
Comparative clinical trial of ultrasound phacoemulsification with and without the WhiteStar system William Fishkind, MD, Brock Bakewell, MD, Eric D. Donnenfeld, MD, Aron D. Rose, MD, L. Andrew Watkins, MD, Randall J. Olson, MD
PURPOSE: To compare the postoperative outcomes of cataract surgery performed with the Sovereign 4.0 system or the Sovereign system with WhiteStar power modulation. SETTING: Ambulatory surgery centers at 4 sites in the United States. METHODS: This was a 3-month, open-label, randomized, parallel-group comparative clinical trial in patients with visually interfering cataract. Surgeons used the divide-and-conquer phacoemulsification technique for nuclear removal. An intraocular lens was implanted using the recommended insertion system. Primary operative outcome measures were equivalent phaco time (EPT), percentage of phaco power, amount of balanced salt solution used, and surgical complications. Patients were seen 1 day and 3 months after surgery. Postoperative outcome measures were the change in endothelial cell count from the preoperative visit to 3 months, corneal clarity, inflammation, and corneal thickness. RESULTS: The Sovereign with WhiteStar group had 48 patients and the Sovereign 4.0 group, 49 patients. Mean EPT and mean percentage of power were significantly lower in the Sovereign with WhiteStar group. Mean EPT was 6.67 seconds G 8.2 (SD) in the Sovereign with WhiteStar group and 8.59 G 9.3 seconds (P Z .01) in the Sovereign 4.0 group. Mean percentage of phaco power was 6.41% G 3.3% in the Sovereign with WhiteStar group and 8.51% G 4.9% in the Sovereign 4.0 group (P Z .01). The Sovereign with WhiteStar group lost significantly fewer endothelial cells (ÿ319.6 G 634.2 cells/mm2) than the Sovereign 4.0 group (ÿ430.3 G 594.6 cells/mm2) (P Z .01). Corneal clarity, cells and flare, and pachymetry were comparable with the exception of the 3-month visit. The mean change in baseline central pachymetry showed significantly less corneal thickening in the Sovereign with WhiteStar group. CONCLUSIONS: The Sovereign with WhiteStar power modulation system provides effective lens removal at lower levels of phaco power and ultrasound energy than the Sovereign 4.0 system. Lower ultrasound levels may reduce the risk for endothelial cell loss during phacoemulsification. J Cataract Refract Surg 2006; 32:45–49 Q 2006 ASCRS and ESCRS
Ultrasound cataract removal opened the door to smallincision cataract surgery for all densities of cataracts, but ultrasound power carries the risk for surgical trauma. Nucleofractis techniques, improved pump systems, vacuumassisted phaco, and interrupted phaco modes have reduced the amount of energy needed to remove the cataract, but ultrasound phacoemulsification continues to be a source of endothelial cell loss1–6 and tissue damage.7 The power to emulsify the lens for removal through the aspiration line comes from the longitudinal excursion of the phacoemulsification needle and ultrasonic power emitted at the tip of the needle. In continuous mode, power is Q 2006 ASCRS and ESCRS Published by Elsevier Inc.
applied continuously with no rest periods. Traditional pulse mode alternates power bursts and rests of equal duration, usually in the range of 50 to 100 msec. The WhiteStar system is a power control enhancement for the Sovereign phaco system. It uses a proprietary algorithm to provide micropulses of energy (microbursts) interspersed with very short periods of no power (microrests) in the range of 4 to12 msec. This pattern of microbursts and microrests produces more cavitation (cutting) energy than traditional continuous pulse or burst modes (M.E. Schafer, MD, ‘‘Cavitation Generation and Cavitational Effects in Phaco,’’ presented at the ASCRS Symposium 0886-3350/06/$-see front matter doi:10.1016/j.jcrs.2005.10.026
45
PHACOEMULSIFICATION WITH AND WITHOUT THE WHITESTAR SYSTEM
on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, April 2003). Microrests allow the tip to dissipate heat and reacquire nuclear fragments. The burst width and rest width are independently variable depending on the surgeon’s technique and preference for speed and power. Continuous power, traditional pulse, and WhiteStar modes are illustrated in Figure 1. The Sovereign system without WhiteStar has continuous pulse and burst modes but does not have micropulse technology. PATIENTS AND METHODS This 3-month, open-label, randomized parallel-group clinical trial compared the Sovereign WhiteStar system with the Sovereign 4.0 system. Five surgeons were to enroll approximately 18 patients for a total of approximately 90 cases. Each patient was randomly assigned to the WhiteStar group (Sovereign with WhiteStar) or the non-WhiteStar group (Sovereign 4.0 Group) according to a randomization schedule prepared by the study sponsor. All investigators were established board-certified cataract surgeons who currently used the WhiteStar System and who, within the past 6 months, used continuous pulse and/or burst modes with the Sovereign 4.0 System. Patients could be enrolled in the study if they had visually interfering senile or presenile cataract for which phacoemulsification extraction was planned. Potential patients were excluded if they had an ocular or systemic condition that would negatively affect the surgical outcome (eg, glaucoma, iritis, history of inflammation, or Fuchs’ dystrophy). Each investigator used his preferred phaco settings, and these were held constant from case to case at that investigator’s site. Preoperative, operative, and postoperative medications were administered according to the standardized regimen defined in the protocol. Surgeons used the divide-and-conquer phacoemulsification technique, applying different technique modifications depending on their level of comfort and expertise. Divide and conquer appeared to be a more popular nucleofractis technique than chopping at the time the study was conducted.8
Accepted for publication July 18, 2005. From the Fishkind and Bakewell Eye Care and Surgery Center (Fishkind, Bakewell), Tucson, Arizona, TLC Laser Eye Centers (Donnenfeld), Garden City, New York, The Eye Care Group (Rose), New Haven, Connecticut, Heights Eye Center (Watkins), Houston, Texas, and John A. Moran Eye Center (Olson), Salt Lake City, Utah, USA. Presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, Philadelphia, Pennsylvania, USA, April 2002. Supported by Advanced Medical Optics, Santa Ana, California, USA.
Figure 1. Graphic representation of continuous power, traditional pulse, and WhiteStar system ultrasound energy patterns in a 500 msec period.
An SI-40NB or SA-40NB intraocular lens (Advanced Medical Optics) was implanted using the Unfolder implantation system recommended for use with these lenses. The preoperative examination required documentation of the patient’s medication regimen, central endothelial cell count, corneal clarity, signs of inflammation, pachymetry (central and midway between the central cornea and limbus near the anticipated wound), intraocular pressure (Goldman applanation), and cataract density according to the nuclear color and opalescence grades of the Lens Opacities Classification System, revision III (LOCSIII)9. Primary operative outcome measures were equivalent phaco time (EPT), percentage of phaco power, amount of balanced salt solution (BSS) used following completion of the prime cycle, and surgical complications. Equivalent phaco time is a measure of the total ultrasound energy used in the procedure. If the power level is held at 50% throughout the procedure and the total time the needle is powered is 20 seconds, EPT is 50% 20 seconds or 10 seconds. Patients were seen at 1 day and 3 months. The postoperative clinical outcome measures were change in endothelial cell count from the preoperative visit to the 3-month visit, corneal clarity, corneal edema, cells and flare, pachymetry, and complications. The investigators determined cell/flare values and corneal clarity using 1 grading technique and were provided with consistent guidelines for classifying slitlamp observations. This study was sized to detect a 0.5 mean difference of grade in corneal clarity between groups with 80% power. Statistical comparisons between group means for the Sovereign with WhiteStar group and Sovereign 4.0 group were made for percentage phaco power used, BSS used, and pachymetry using the 2-sample t test. The Wilcoxon rank sum test was used to compare groups for EPT, change in endothelial cell count, signs of inflammation, and corneal clarity because these data are not normally distributed. Two-sided testing was performed with alpha set at 0.05.
No author has a financial or proprietary interest in any material or method mentioned.
RESULTS
Reprint requests to William J. Fishkind, MD, Fishkind and Bakewell Eye Care and Surgery Center, 5599 North Oracle Road, Tucson, Arizona 85704-3821, USA. E-mail: [email protected].
This study was conducted between November 2001 and April 2002. A total of 97 patients were enrolled at the
46
J CATARACT REFRACT SURG - VOL 32, JANUARY 2006
5 sites. Forty-eight patients were randomly assigned to the Sovereign with WhiteStar group and 49 to the Sovereign 4.0 group. Patients were followed for 3 months after surgery. Operative Variables
Table 1 shows the results for the operative variables. Mean EPT and mean percentage of power were significantly lower in the Sovereign with WhiteStar group than in the Sovereign 4.0 group (P Z.01). No operative parameter showed statistically significant differences when analyzed by grade of cataract. Most of the cataracts in both groups were grades 2C to 4C. The Sovereign with WhiteStar group had 2 cataracts at grade 1C, 5 at grade 5C, and 1 at grade 6C. The Sovereign 4.0 group had none at grade 1C, 1 at 5C, and none at 6C. No statistically significant differences were found in the amount of BSS used. Two patients (2/97; 2.1%) had operative complications, neither of which was technique related or machine related. One patient (Sovereign with WhiteStar group) had an unexpectedly complicated surgery due to zonular dehiscence and a very dense (4C) nucleus. At 3 months, the endothelial cell count and pachymetry were within normal limits, the cornea was clear (grade 0), and there were no complications. The second patient (Sovereign 4.0 group) had a very dense cataract (4C) and posterior capsule tear. At 3 months, endothelial cell count and pachymetry were within normal limits, the cornea clarity was grade 1, and there were no complications.
Endothelial cell count (cells/mm2)
PHACOEMULSIFICATION WITH AND WITHOUT THE WHITESTAR SYSTEM
0
WS Group
4.0 Group
-200 -400 -600 -800 -1000 -1200
P=0.01
Figure 2. Change in mean endothelial cell count from preoperative visit to 3 months.
Sovereign with WhiteStar group had grade 2 corneal clarity at the 3-month visit. This patient had guttata preoperatively and at all postoperative visits. Central and mid-pachymetry values were similar between the groups at both postoperative visits. The mean change in central pachymetry from baseline showed slightly less central corneal thickening in the Sovereign with WhiteStar group at 3 months. The difference from preoperative baseline was ÿ0.012 G 0.022 mm (SD) in the Sovereign with WhiteStar group and 0.001 G 0.025 mm in the Sovereign 4.0 Group (P Z.009) (Figure 3). No statistically significant between-group differences were identified for cells or flare. Most patients had 0 or C1 (trace) cells and 0 or C1 (trace) flare. Table 2 indicates postoperative corneal clarity and cell/flare value scores. No postoperative complications occurred in any patient.
Postoperative Variables
Table 1. Operative parameters.
Operative Parameters EPT (s) Phaco power (%) Amount of BSS used/case (mL)
Sovereign with WhiteStar Group (n Z 48)
Sovereign 4.0 Group (n Z 49)
P Value
6.67 G 8.2 6.41 G 3.3 128.75 G 55.2
8.59 G 9.3 8.51 G 4.9 140.82 G 64.7
.01* .01* .33†
Means G SD EPT Z equivalent phacotime *Wilcoxon rank sum † t test
DISCUSSION
The most interesting finding in this study was significantly less loss of endothelial cells in the Sovereign with 0.03 0.02
Pachymetry (um)
The Sovereign with WhiteStar group lost significantly fewer endothelial cells than the Sovereign 4.0 Group (Figure 2). Corneal clarity was comparable at all grades in the Sovereign with WhiteStar group and Sovereign 4.0 group at 1 day and 3 months (P Z .34). One patient in the
0.01 0.001
0 WS group
4.0 group
-0.01 -0.012 -0.02 -0.03 -0.04
P=0.009
Figure 3. Change in central pachymetry from preoperative visit to 3 months.
J CATARACT REFRACT SURG - VOL 32, JANUARY 2006
47
PHACOEMULSIFICATION WITH AND WITHOUT THE WHITESTAR SYSTEM
Table 2. Postoperative variables: distribution of corneal clarity and cell flare scores.
Grade, Percentage Parameter
None Trace Mild Moderate Severe (0) (1) (2) (3) (4)
Corneal clarity, 1 day 37.5 Sovereign with WhiteStar group (n Z 48) WhiteStar 4.0 group 29.2 (n Z 48) Corneal clarity, 3 months 93.6 Sovereign with WhiteStar group (n Z 47) WhiteStar 4.0 group 87.5 (n Z 48) Cell flare, 1 day Sovereign with 6.5 WhiteStar group (n Z 46) WhiteStar 4.0 group 6.3 (n Z 48) Cell flare, 3 months Sovereign with 4.3 WhiteStar group (n Z 46) WhiteStar 4.0 group 6.3 (n Z 48)
45.8
10.4
4.2
2.1
47.9
16.7
4.2
2.1
4.2
2.1
0.0
0.0
12.5
0.0
0.0
0.0
76.1
17.4
0.0
0.0
85.4
8.3
0.0
0.0
84.8
10.9
0.0
0.0
85.4
8.3
0.0
0.0
WhiteStar group. Minimizing endothelial cell damage is of paramount importance during phacoemulsification, as iatrogenic cell loss may occur with excessive intraocular manipulation, ultrasonic vibration, and heat generated by the phaco tip. Phacoemulsification using Sovereign with Whitestar software was faster and more energy efficient than surgery using the 4.0 system. The Sovereign with WhiteStar group had statistically significant lower EPT and lower phaco power despite having denser cataracts than the Sovereign 4.0 group. These findings may indicate a correlation between lower ultrasound levels introduced into the eye and less trauma to the corneal endothelium. This is consistent with previous reports6,10–13 evaluating ultrasound power levels, risk for thermal damage to the cornea, and the level of turbulence generated by the WhiteStar power modulations. Olson10 used a 21-gauge phaco needle, 21-gauge horizontal irrigating chopper, and bimanual technique with the Sovereign WhiteStar system in 18 consecutive patients with dense cataracts of 3C to 4C on a 4-point scale. Mean EPT was 1.4 G 1.3 seconds and mean phaco power level was 2.4% G 0.9%.
48
Soscia et al.11 tested the temperature-elevation effect of the WhiteStar system using a 19-gauge bare phaco needle in 2 fresh human eyebank eyes. They inserted a microthermister at the wound site to monitor temperature and applied full continuous power for 3 minutes followed by occluding 1 and then both fluid lines. At 100% continuous power with unoccluded lines, the maximum temperature reached 27.3 C. When the aspiration line was occluded and the irrigation line remained unoccluded, the temperature did not rise above 32.5 C. Only when both the aspiration and flow lines were occluded did the temperature rise to 45 C with continuous power. Donnenfeld et al.12 ran a temperature elevation test in 10 patients having bimanual phacoemulsification. All cataracts were nuclear sclerotic and grade 2 or 3 on a scale of 0 to 4. They inserted a thermocouple thermometer wire into the clear cornea directly adjacent to the wound and removed the cataracts with a 20-gauge needle without an irrigation sleeve. The maximum corneal wound temperature ranged from 24 C to 34 C. Eyes maintained corneal clarity with no signs of thermal damage to the wound. The endothelial cell loss at 3 months was 7%. In 2002, Tsuneoka et al.6 reported on endothelial cell loss in a large study comprising 637 eyes. They used a 20gauge or 21-gauge sleeveless phaco needle to remove the crystalline lens through a 1.4 mm incision using 4 different phaco machines, Legacy 20000 (Alcon), Sovereign, CV24000 (Nidek), and Pulser (Optikon). The mean operating time was 8 minutes, 42 seconds, with harder cataracts requiring the longer surgery time and more infusion solution. Endothelial cell counts in 312 eyes (48.9% of eyes in the study) at 3 months or later showed a loss of cells associated with cataract densities. Mean endothelial cell counts decreased by 4.6% in eyes with grade 1, 6.9% in eyes with grade 2, 10.8% in eyes with grade 3, and 15.6% in eyes with grade 4 or higher cataract densities (using the Emery-Little classification of nuclear hardness). In the current study, no significant differences were observed between groups in postoperative corneal clarity grade or change in corneal clarity from preoperatively, indicating that the WhiteStar system is comparable to 4.0 software regarding the maintenance of good corneal clarity. It should be noted that a higher percentage of eyes in the Sovereign with WhiteStar group had corneal clarity rated at grade 0 (clear) at 1 day and 3 months than in the Sovereign 4.0 group. This may be correlated with power itself or with the effect that power modulations have on fluid flow inside the anterior chamber. Oki13 used a model of the anterior chamber to examine the effect of 4 power modesdcontinuous, short pulse, and WhiteStar DB and CFdon fluid flow inside the chamber. The rapid back and forth excursions of the phaco needle generated dynamic waves that vibrated
J CATARACT REFRACT SURG - VOL 32, JANUARY 2006
PHACOEMULSIFICATION WITH AND WITHOUT THE WHITESTAR SYSTEM
against the interior surface of the chamber. The vibration velocity and amplitude of displacement of the outer surface of the chamber were captured by laser Doppler vibrometry. Fluid flow inside the chamber was captured at 4000 frames per second by Schlieren photography. The WhiteStar CF setting produced half the peak vibration velocity and half the displacement amplitude of continuous mode. Schlieren photography showed intense pressure waves with continuous and short pulse modes and substantially diminished waves with both WhiteStar modes. These tests showed that pressure waves created with the WhiteStar system had a more modest impact on the inner aspect of the anterior chamber model than traditional power modes. Steinert and Schafer (R.F. Steinert, ‘‘Thermal Energy and Turbulence with WhiteStar and Conventional Phacoemulsification,’’ presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, April 2003) used high-resolution digital ultrasound imaging to analyze fluid velocity and motion at the phaco tip using Sovereign continuous power and WhiteStar CF settings in a model of the anterior chamber. They used a 20-gauge tip, flow set at 40 cc/second, vacuum at 200 mm Hg, and power settings of 25%, 40%, 55%, and 70%. Fluid velocity correlated positively with higher phaco powers. The WhiteStar CF mode had decreased fluid velocity away from the tip than the continuous power mode at all 4 power settings. Fluid flow moving away from the tip in the presence of aspiration flow of 40 cc/second may aid in keeping nuclear fragments near the tip and away from the corneal endothelium. The differences between groups in mean change in pachymetry were statistically significant at 3 months for central pachymetry. The WhiteStar group had less central thickness (edema) than the 4.0 group. Although the difference was too small to be clinically significant in either group, less central corneal thickening at 3 months may indicate better postoperative recovery in the WhiteStar group than in the 4.0 group. The current study demonstrates that the Sovereign with WhiteStar power modulation system provides effective lens
removal at lower levels of phaco power and ultrasound energy than the Sovereign 4.0 system. Lower ultrasound levels may have a protective effect on the corneal endothelium directly or by the effect that the ultrasound power modulations exert on the surgical environment.
REFERENCES 1. Dick HB, Kohnen T, Jacobi FK, et al. Long-term endothelial cell loss following phacoemulsification through a temporal clear corneal incision. J Cataract Refract Surg 1996; 22:63–71 2. Hayashi K, Hayashi H, Nakao F, et al. Risk factors for corneal endothelial injury during phacoemulsification. J Cataract Refract Surg 1996; 22: 1079–1084 3. Dı´az-Valle D, Benı´tez del Castillo Sa´nchez JM, Castillo A, et al. Endothelial damage with cataract surgery techniques. J Cataract Refract Surg 1998; 24:951–955 4. Vajpayee RB, Kumar A, Dada T, et al. Phaco-chop versus stop-andchop nucleotomy for phacoemulsification. J Cataract Refract Surg 2000; 26:1638–1641 5. Beltrame G, Salvetat ML, Driussi G, et al. Effect of incision size and site on corneal endothelial changes in cataract surgery. J Cataract Refract Surg 2002; 28:118–125 6. Tsuneoka H, Shiba T, Takahashi Y. Ultrasonic phacoemulsification using a 1.4 mm incision: clinical results. J Cataract Refract Surg 2002; 28:81–86 7. Sugar A, Schertzer RM. Clinical course of phacoemulsification wound burns. J Cataract Refract Surg 1999; 25:688–692 8. Leaming DV. Practice styles and preferences of ASCRS membersd2001 survey. J Cataract Refract Surg 2002; 28:1681–1688 9. Chylack LT Jr, Wolfe JK, Singer D, et al. The Lens Opacities Classification System III; the Longitudinal Study of Cataract Study Group. Arch Ophthalmol 1993; 111:831–836 10. Olson RJ. Clinical experience with 21-gauge manual microphacoemulsification using Sovereign WhiteStar technology in eyes with dense cataract. J Cataract Refract Surg 2004; 30:168–172 11. Soscia W, Howard JG, Olson RJ. Microphacoemulsification with WhiteStar; a wound-temperature study. J Cataract Refract Surg 2002; 28:1044–1046 12. Donnenfeld ED, Olson RJ, Solomon R, et al. Efficacy and wound-temperature gradient of WhiteStar phacoemulsification through a 1.2 mm incision. J Cataract Refract Surg 2003; 29:1097–1100 13. Oki K. Measuring rectilinear flow within the anterior chamber in phacoemulsification procedures. J Cataract Refract Surg 2004; 30: 1759–1767
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49
Comparative clinical trial of ultrasound phacoemulsification with and without the WhiteStar system William Fishkind, MD, Brock Bakewell, MD, Eric D. Donnenfeld, MD, Aron D. Rose, MD, L. Andrew Watkins, MD, Randall J. Olson, MD
PURPOSE: To compare the postoperative outcomes of cataract surgery performed with the Sovereign 4.0 system or the Sovereign system with WhiteStar power modulation. SETTING: Ambulatory surgery centers at 4 sites in the United States. METHODS: This was a 3-month, open-label, randomized, parallel-group comparative clinical trial in patients with visually interfering cataract. Surgeons used the divide-and-conquer phacoemulsification technique for nuclear removal. An intraocular lens was implanted using the recommended insertion system. Primary operative outcome measures were equivalent phaco time (EPT), percentage of phaco power, amount of balanced salt solution used, and surgical complications. Patients were seen 1 day and 3 months after surgery. Postoperative outcome measures were the change in endothelial cell count from the preoperative visit to 3 months, corneal clarity, inflammation, and corneal thickness. RESULTS: The Sovereign with WhiteStar group had 48 patients and the Sovereign 4.0 group, 49 patients. Mean EPT and mean percentage of power were significantly lower in the Sovereign with WhiteStar group. Mean EPT was 6.67 seconds G 8.2 (SD) in the Sovereign with WhiteStar group and 8.59 G 9.3 seconds (P Z .01) in the Sovereign 4.0 group. Mean percentage of phaco power was 6.41% G 3.3% in the Sovereign with WhiteStar group and 8.51% G 4.9% in the Sovereign 4.0 group (P Z .01). The Sovereign with WhiteStar group lost significantly fewer endothelial cells (ÿ319.6 G 634.2 cells/mm2) than the Sovereign 4.0 group (ÿ430.3 G 594.6 cells/mm2) (P Z .01). Corneal clarity, cells and flare, and pachymetry were comparable with the exception of the 3-month visit. The mean change in baseline central pachymetry showed significantly less corneal thickening in the Sovereign with WhiteStar group. CONCLUSIONS: The Sovereign with WhiteStar power modulation system provides effective lens removal at lower levels of phaco power and ultrasound energy than the Sovereign 4.0 system. Lower ultrasound levels may reduce the risk for endothelial cell loss during phacoemulsification. J Cataract Refract Surg 2006; 32:45–49 Q 2006 ASCRS and ESCRS
Ultrasound cataract removal opened the door to smallincision cataract surgery for all densities of cataracts, but ultrasound power carries the risk for surgical trauma. Nucleofractis techniques, improved pump systems, vacuumassisted phaco, and interrupted phaco modes have reduced the amount of energy needed to remove the cataract, but ultrasound phacoemulsification continues to be a source of endothelial cell loss1–6 and tissue damage.7 The power to emulsify the lens for removal through the aspiration line comes from the longitudinal excursion of the phacoemulsification needle and ultrasonic power emitted at the tip of the needle. In continuous mode, power is Q 2006 ASCRS and ESCRS Published by Elsevier Inc.
applied continuously with no rest periods. Traditional pulse mode alternates power bursts and rests of equal duration, usually in the range of 50 to 100 msec. The WhiteStar system is a power control enhancement for the Sovereign phaco system. It uses a proprietary algorithm to provide micropulses of energy (microbursts) interspersed with very short periods of no power (microrests) in the range of 4 to12 msec. This pattern of microbursts and microrests produces more cavitation (cutting) energy than traditional continuous pulse or burst modes (M.E. Schafer, MD, ‘‘Cavitation Generation and Cavitational Effects in Phaco,’’ presented at the ASCRS Symposium 0886-3350/06/$-see front matter doi:10.1016/j.jcrs.2005.10.026
45
PHACOEMULSIFICATION WITH AND WITHOUT THE WHITESTAR SYSTEM
on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, April 2003). Microrests allow the tip to dissipate heat and reacquire nuclear fragments. The burst width and rest width are independently variable depending on the surgeon’s technique and preference for speed and power. Continuous power, traditional pulse, and WhiteStar modes are illustrated in Figure 1. The Sovereign system without WhiteStar has continuous pulse and burst modes but does not have micropulse technology. PATIENTS AND METHODS This 3-month, open-label, randomized parallel-group clinical trial compared the Sovereign WhiteStar system with the Sovereign 4.0 system. Five surgeons were to enroll approximately 18 patients for a total of approximately 90 cases. Each patient was randomly assigned to the WhiteStar group (Sovereign with WhiteStar) or the non-WhiteStar group (Sovereign 4.0 Group) according to a randomization schedule prepared by the study sponsor. All investigators were established board-certified cataract surgeons who currently used the WhiteStar System and who, within the past 6 months, used continuous pulse and/or burst modes with the Sovereign 4.0 System. Patients could be enrolled in the study if they had visually interfering senile or presenile cataract for which phacoemulsification extraction was planned. Potential patients were excluded if they had an ocular or systemic condition that would negatively affect the surgical outcome (eg, glaucoma, iritis, history of inflammation, or Fuchs’ dystrophy). Each investigator used his preferred phaco settings, and these were held constant from case to case at that investigator’s site. Preoperative, operative, and postoperative medications were administered according to the standardized regimen defined in the protocol. Surgeons used the divide-and-conquer phacoemulsification technique, applying different technique modifications depending on their level of comfort and expertise. Divide and conquer appeared to be a more popular nucleofractis technique than chopping at the time the study was conducted.8
Accepted for publication July 18, 2005. From the Fishkind and Bakewell Eye Care and Surgery Center (Fishkind, Bakewell), Tucson, Arizona, TLC Laser Eye Centers (Donnenfeld), Garden City, New York, The Eye Care Group (Rose), New Haven, Connecticut, Heights Eye Center (Watkins), Houston, Texas, and John A. Moran Eye Center (Olson), Salt Lake City, Utah, USA. Presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, Philadelphia, Pennsylvania, USA, April 2002. Supported by Advanced Medical Optics, Santa Ana, California, USA.
Figure 1. Graphic representation of continuous power, traditional pulse, and WhiteStar system ultrasound energy patterns in a 500 msec period.
An SI-40NB or SA-40NB intraocular lens (Advanced Medical Optics) was implanted using the Unfolder implantation system recommended for use with these lenses. The preoperative examination required documentation of the patient’s medication regimen, central endothelial cell count, corneal clarity, signs of inflammation, pachymetry (central and midway between the central cornea and limbus near the anticipated wound), intraocular pressure (Goldman applanation), and cataract density according to the nuclear color and opalescence grades of the Lens Opacities Classification System, revision III (LOCSIII)9. Primary operative outcome measures were equivalent phaco time (EPT), percentage of phaco power, amount of balanced salt solution (BSS) used following completion of the prime cycle, and surgical complications. Equivalent phaco time is a measure of the total ultrasound energy used in the procedure. If the power level is held at 50% throughout the procedure and the total time the needle is powered is 20 seconds, EPT is 50% 20 seconds or 10 seconds. Patients were seen at 1 day and 3 months. The postoperative clinical outcome measures were change in endothelial cell count from the preoperative visit to the 3-month visit, corneal clarity, corneal edema, cells and flare, pachymetry, and complications. The investigators determined cell/flare values and corneal clarity using 1 grading technique and were provided with consistent guidelines for classifying slitlamp observations. This study was sized to detect a 0.5 mean difference of grade in corneal clarity between groups with 80% power. Statistical comparisons between group means for the Sovereign with WhiteStar group and Sovereign 4.0 group were made for percentage phaco power used, BSS used, and pachymetry using the 2-sample t test. The Wilcoxon rank sum test was used to compare groups for EPT, change in endothelial cell count, signs of inflammation, and corneal clarity because these data are not normally distributed. Two-sided testing was performed with alpha set at 0.05.
No author has a financial or proprietary interest in any material or method mentioned.
RESULTS
Reprint requests to William J. Fishkind, MD, Fishkind and Bakewell Eye Care and Surgery Center, 5599 North Oracle Road, Tucson, Arizona 85704-3821, USA. E-mail: [email protected].
This study was conducted between November 2001 and April 2002. A total of 97 patients were enrolled at the
46
J CATARACT REFRACT SURG - VOL 32, JANUARY 2006
5 sites. Forty-eight patients were randomly assigned to the Sovereign with WhiteStar group and 49 to the Sovereign 4.0 group. Patients were followed for 3 months after surgery. Operative Variables
Table 1 shows the results for the operative variables. Mean EPT and mean percentage of power were significantly lower in the Sovereign with WhiteStar group than in the Sovereign 4.0 group (P Z.01). No operative parameter showed statistically significant differences when analyzed by grade of cataract. Most of the cataracts in both groups were grades 2C to 4C. The Sovereign with WhiteStar group had 2 cataracts at grade 1C, 5 at grade 5C, and 1 at grade 6C. The Sovereign 4.0 group had none at grade 1C, 1 at 5C, and none at 6C. No statistically significant differences were found in the amount of BSS used. Two patients (2/97; 2.1%) had operative complications, neither of which was technique related or machine related. One patient (Sovereign with WhiteStar group) had an unexpectedly complicated surgery due to zonular dehiscence and a very dense (4C) nucleus. At 3 months, the endothelial cell count and pachymetry were within normal limits, the cornea was clear (grade 0), and there were no complications. The second patient (Sovereign 4.0 group) had a very dense cataract (4C) and posterior capsule tear. At 3 months, endothelial cell count and pachymetry were within normal limits, the cornea clarity was grade 1, and there were no complications.
Endothelial cell count (cells/mm2)
PHACOEMULSIFICATION WITH AND WITHOUT THE WHITESTAR SYSTEM
0
WS Group
4.0 Group
-200 -400 -600 -800 -1000 -1200
P=0.01
Figure 2. Change in mean endothelial cell count from preoperative visit to 3 months.
Sovereign with WhiteStar group had grade 2 corneal clarity at the 3-month visit. This patient had guttata preoperatively and at all postoperative visits. Central and mid-pachymetry values were similar between the groups at both postoperative visits. The mean change in central pachymetry from baseline showed slightly less central corneal thickening in the Sovereign with WhiteStar group at 3 months. The difference from preoperative baseline was ÿ0.012 G 0.022 mm (SD) in the Sovereign with WhiteStar group and 0.001 G 0.025 mm in the Sovereign 4.0 Group (P Z.009) (Figure 3). No statistically significant between-group differences were identified for cells or flare. Most patients had 0 or C1 (trace) cells and 0 or C1 (trace) flare. Table 2 indicates postoperative corneal clarity and cell/flare value scores. No postoperative complications occurred in any patient.
Postoperative Variables
Table 1. Operative parameters.
Operative Parameters EPT (s) Phaco power (%) Amount of BSS used/case (mL)
Sovereign with WhiteStar Group (n Z 48)
Sovereign 4.0 Group (n Z 49)
P Value
6.67 G 8.2 6.41 G 3.3 128.75 G 55.2
8.59 G 9.3 8.51 G 4.9 140.82 G 64.7
.01* .01* .33†
Means G SD EPT Z equivalent phacotime *Wilcoxon rank sum † t test
DISCUSSION
The most interesting finding in this study was significantly less loss of endothelial cells in the Sovereign with 0.03 0.02
Pachymetry (um)
The Sovereign with WhiteStar group lost significantly fewer endothelial cells than the Sovereign 4.0 Group (Figure 2). Corneal clarity was comparable at all grades in the Sovereign with WhiteStar group and Sovereign 4.0 group at 1 day and 3 months (P Z .34). One patient in the
0.01 0.001
0 WS group
4.0 group
-0.01 -0.012 -0.02 -0.03 -0.04
P=0.009
Figure 3. Change in central pachymetry from preoperative visit to 3 months.
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PHACOEMULSIFICATION WITH AND WITHOUT THE WHITESTAR SYSTEM
Table 2. Postoperative variables: distribution of corneal clarity and cell flare scores.
Grade, Percentage Parameter
None Trace Mild Moderate Severe (0) (1) (2) (3) (4)
Corneal clarity, 1 day 37.5 Sovereign with WhiteStar group (n Z 48) WhiteStar 4.0 group 29.2 (n Z 48) Corneal clarity, 3 months 93.6 Sovereign with WhiteStar group (n Z 47) WhiteStar 4.0 group 87.5 (n Z 48) Cell flare, 1 day Sovereign with 6.5 WhiteStar group (n Z 46) WhiteStar 4.0 group 6.3 (n Z 48) Cell flare, 3 months Sovereign with 4.3 WhiteStar group (n Z 46) WhiteStar 4.0 group 6.3 (n Z 48)
45.8
10.4
4.2
2.1
47.9
16.7
4.2
2.1
4.2
2.1
0.0
0.0
12.5
0.0
0.0
0.0
76.1
17.4
0.0
0.0
85.4
8.3
0.0
0.0
84.8
10.9
0.0
0.0
85.4
8.3
0.0
0.0
WhiteStar group. Minimizing endothelial cell damage is of paramount importance during phacoemulsification, as iatrogenic cell loss may occur with excessive intraocular manipulation, ultrasonic vibration, and heat generated by the phaco tip. Phacoemulsification using Sovereign with Whitestar software was faster and more energy efficient than surgery using the 4.0 system. The Sovereign with WhiteStar group had statistically significant lower EPT and lower phaco power despite having denser cataracts than the Sovereign 4.0 group. These findings may indicate a correlation between lower ultrasound levels introduced into the eye and less trauma to the corneal endothelium. This is consistent with previous reports6,10–13 evaluating ultrasound power levels, risk for thermal damage to the cornea, and the level of turbulence generated by the WhiteStar power modulations. Olson10 used a 21-gauge phaco needle, 21-gauge horizontal irrigating chopper, and bimanual technique with the Sovereign WhiteStar system in 18 consecutive patients with dense cataracts of 3C to 4C on a 4-point scale. Mean EPT was 1.4 G 1.3 seconds and mean phaco power level was 2.4% G 0.9%.
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Soscia et al.11 tested the temperature-elevation effect of the WhiteStar system using a 19-gauge bare phaco needle in 2 fresh human eyebank eyes. They inserted a microthermister at the wound site to monitor temperature and applied full continuous power for 3 minutes followed by occluding 1 and then both fluid lines. At 100% continuous power with unoccluded lines, the maximum temperature reached 27.3 C. When the aspiration line was occluded and the irrigation line remained unoccluded, the temperature did not rise above 32.5 C. Only when both the aspiration and flow lines were occluded did the temperature rise to 45 C with continuous power. Donnenfeld et al.12 ran a temperature elevation test in 10 patients having bimanual phacoemulsification. All cataracts were nuclear sclerotic and grade 2 or 3 on a scale of 0 to 4. They inserted a thermocouple thermometer wire into the clear cornea directly adjacent to the wound and removed the cataracts with a 20-gauge needle without an irrigation sleeve. The maximum corneal wound temperature ranged from 24 C to 34 C. Eyes maintained corneal clarity with no signs of thermal damage to the wound. The endothelial cell loss at 3 months was 7%. In 2002, Tsuneoka et al.6 reported on endothelial cell loss in a large study comprising 637 eyes. They used a 20gauge or 21-gauge sleeveless phaco needle to remove the crystalline lens through a 1.4 mm incision using 4 different phaco machines, Legacy 20000 (Alcon), Sovereign, CV24000 (Nidek), and Pulser (Optikon). The mean operating time was 8 minutes, 42 seconds, with harder cataracts requiring the longer surgery time and more infusion solution. Endothelial cell counts in 312 eyes (48.9% of eyes in the study) at 3 months or later showed a loss of cells associated with cataract densities. Mean endothelial cell counts decreased by 4.6% in eyes with grade 1, 6.9% in eyes with grade 2, 10.8% in eyes with grade 3, and 15.6% in eyes with grade 4 or higher cataract densities (using the Emery-Little classification of nuclear hardness). In the current study, no significant differences were observed between groups in postoperative corneal clarity grade or change in corneal clarity from preoperatively, indicating that the WhiteStar system is comparable to 4.0 software regarding the maintenance of good corneal clarity. It should be noted that a higher percentage of eyes in the Sovereign with WhiteStar group had corneal clarity rated at grade 0 (clear) at 1 day and 3 months than in the Sovereign 4.0 group. This may be correlated with power itself or with the effect that power modulations have on fluid flow inside the anterior chamber. Oki13 used a model of the anterior chamber to examine the effect of 4 power modesdcontinuous, short pulse, and WhiteStar DB and CFdon fluid flow inside the chamber. The rapid back and forth excursions of the phaco needle generated dynamic waves that vibrated
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against the interior surface of the chamber. The vibration velocity and amplitude of displacement of the outer surface of the chamber were captured by laser Doppler vibrometry. Fluid flow inside the chamber was captured at 4000 frames per second by Schlieren photography. The WhiteStar CF setting produced half the peak vibration velocity and half the displacement amplitude of continuous mode. Schlieren photography showed intense pressure waves with continuous and short pulse modes and substantially diminished waves with both WhiteStar modes. These tests showed that pressure waves created with the WhiteStar system had a more modest impact on the inner aspect of the anterior chamber model than traditional power modes. Steinert and Schafer (R.F. Steinert, ‘‘Thermal Energy and Turbulence with WhiteStar and Conventional Phacoemulsification,’’ presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, April 2003) used high-resolution digital ultrasound imaging to analyze fluid velocity and motion at the phaco tip using Sovereign continuous power and WhiteStar CF settings in a model of the anterior chamber. They used a 20-gauge tip, flow set at 40 cc/second, vacuum at 200 mm Hg, and power settings of 25%, 40%, 55%, and 70%. Fluid velocity correlated positively with higher phaco powers. The WhiteStar CF mode had decreased fluid velocity away from the tip than the continuous power mode at all 4 power settings. Fluid flow moving away from the tip in the presence of aspiration flow of 40 cc/second may aid in keeping nuclear fragments near the tip and away from the corneal endothelium. The differences between groups in mean change in pachymetry were statistically significant at 3 months for central pachymetry. The WhiteStar group had less central thickness (edema) than the 4.0 group. Although the difference was too small to be clinically significant in either group, less central corneal thickening at 3 months may indicate better postoperative recovery in the WhiteStar group than in the 4.0 group. The current study demonstrates that the Sovereign with WhiteStar power modulation system provides effective lens
removal at lower levels of phaco power and ultrasound energy than the Sovereign 4.0 system. Lower ultrasound levels may have a protective effect on the corneal endothelium directly or by the effect that the ultrasound power modulations exert on the surgical environment.
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