ARTICLE Comparison of the effect of AquaLase and NeoSoniX phacoemulsification on the corneal endothelium Nada Jirásková, MD, PhD, Jana Kadlecová, MD, Pavel Rozsı́val, MD, PhD, Jana Nekolová, MD, Jana Pozlerova, MD, Zlatica Dúbravská, MD PURPOSE: To compare the extent of corneal endothelial cell loss and pachymetry changes in 2 age-based groups of patients who had cataract removal by AquaLase (Alcon) phacoemulsification in 1 eye and NeoSoniX (Alcon) phacoemulsification in the contralateral eye. SETTING: Department of Ophthalmology, University Hospital, Hradec Králové, Czech Republic. METHODS: This prospective clinical study comprised 28 patients younger than 80 years (Group A) and 28 patients 80 years or older (Group B) with bilateral cataract having lens removal using AquaLase in the right eye and NeoSoniX in the left eye. The nuclei were graded clinically on the basis of hardness. The endothelial cell count (ECC), pachymetry, and best corrected visual acuity (BCVA) were evaluated preoperatively and postoperatively. The mean ECC and pachymetry values (GSD) were calculated in each group, with differences between right and left eyes analyzed using the paired t test. RESULTS: In Group A, the differences in the postoperative changes in ECC and pachymetry between AquaLase and NeoSoniX were not statistically significant. In Group B, there were statistically significant differences in postoperative changes in ECC and pachymetry, with the results better in the AquaLase eyes. The BCVA immediately after surgery was better than preoperatively in all eyes. CONCLUSION: The results suggest that AquaLase cataract extraction is safe for the endothelium, even in older patients with harder cataracts and a lower ECC count preoperatively. J Cataract Refract Surg 2008; 34:377–382 Q 2008 ASCRS and ESCRS Phacoemulsification is now the preferred technique for cataract removal.1–4 Continuous improvement in technology and technique have made cataract surgery safer and more efficient.5–7 The quest for lens extraction with reduced intraocular energy resulted in power modulations and supplemental energy sources, which have improved outcomes.8–10 Conventional ultrasound (US) phacoemulsification is created in a handpiece when power is applied to piezoelectric crystals that convert the electrical energy into mechanical vibrations of the phaco needle. The phaco needle tip is used to emulsify the lens material at US frequencies generally between 25 KHz and 62 KHz, which creates thermal and cavitational energy that has the potential to damage the cornea. The NeoSoniX handpiece (Alcon) delivers oscillatory sonic and axial US energy separately or in combination. The phaco tip has a variable rotational oscillation up to 2 degrees at an approximate frequency of 100 Hz. This lower frequency does not produce significant thermal Q 2008 ASCRS and ESCRS Published by Elsevier Inc. energy and thus minimizes the risk for thermal injury. Previous studies11 suggest that US coupled with oscillatory motion is more efficient than axial energy alone. The AquaLase liquefaction device (Alcon), one of the more recent phacoemulsification technologies, uses warm pulses (57 C) of balanced salt solution (BSS) to strain and dissolve the lens for aspiration. Within the AquaLase handpiece, 4 mL fluid pulses are generated as current passes between electrodes. These pulses then travel from the handpiece into the tip of the instrument and eventually into the eye. The fluid pulses pass through a channel in the outer sleeve of the tip and exit through a single small opening located in the lumen of the polymer application tip near its distal end. Aspiration of the liquefied lens material occurs through the central lumen of the tip. The BSS pulses are delivered at a maximum rate of 50 Hz, and the magnitude of the pulses can be linearly controlled by depressing the footpedal. 0886-3350/08/$dsee front matter doi:10.1016/j.jcrs.2007.10.033 377 378 EFFECT OF AQUALASE AND NEOSONIX ON CORNEAL ENDOTHELIUM The purpose of this study was to evaluate the effect of AquaLase and NeoSoniX technology on corneal endothelial cells during phacoemulsification. PATIENTS AND METHODS This prospective clinical study included patients with bilateral lens opacification scheduled for cataract surgery at the Department of Ophthalmology, University Hospital, Hradec Králové. Patients were selected from the department queue. For patients to be eligible for the study, both eyes had to have cataract, preferably with similar density grades. Patients with ocular surface disease, endothelial or stromal corneal dystrophy, or corneal scars were excluded. The study purpose, procedures, and responsibilities were explained to all potential participants, and informed consent was obtained from all selected patients. Patients were divided into 2 groups based on age. Group A comprised patients younger than 80 years and Group B, patients 80 years or older. Before surgery, a complete eye examination was performed. The examination included distance best corrected visual acuity (BCVA) using Snellen optotypes, endothelial cell density (ECD), and pachymetry using a specular microscope (Noncon Robo Pachy SP-9000, Konan Medical). Cataracts were graded clinically on the basis of hardness according to the Buratto classification2 (1 to 5 scale). Patients with a very hard nucleus (grade 5 to brown or black rock hard cataracts) were not included in the study. Surgery was performed by 1 of 2 surgeons (N.J., P.R.); both eyes of each patient were operated on by the same surgeon. Phacoemulsification was performed using topical anesthesia, a 3.0 mm limbal incision, and AquaLase in the right eye and NeoSoniX in the left eye. The standard soft polymer needle (flared at the tip) with a 1.10 mm inner diameter and 1.32 mm outer diameter was used in all AquaLase cases and a 30-degree round 1.10 mm flared ABS tip, in all NeoSoniX cases. The phaco settings were modified for each cataract grade with both lens removal modalities (Tables 1A and 1B). Sodium hyaluronate 3%–chondroitin sulfate 4% with sodium hyaluronate 1% (DuoVisc) was used as an ophthalmic viscosurgical device (OVD) in all eyes. The dispersive OVD (sodium hyaluronate 3.0%–chondroitin sulfate 4.0% [Viscoat]) was used during creation of the capsulorhexis and the cohesive OVD (sodium hyaluronate 1.0% Accepted for publication October 23, 2007. From the Department of Ophthalmology, University Hospital, Hradec Králové, Czech Republic. No author has a financial or proprietary interest in any material or method mentioned. Presented in part at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Diego, California, USA, April 2007. Supported in part by research project MZO 00179906 from the Ministry of Health, Prague, Czech Republic, and in part by a grant from Alcon, Fort Worth, Texas, USA. Corresponding author: Nada Jirásková, MD, PhD, Department of Ophthalmology, University Hospital, Sokolska 581, 500 05 Hradec Králové, Czech Republic. E-mail: jirasnad@fnhk.cz. [Provisc]), for intraocular lens (IOL) insertion. In all eyes, a single-piece IOL (AcrySof, Alcon) was implanted in the bag using the Monarch II injector system. Postoperatively, all patients received topical tobramycin 3.0 mg/mL–dexamethasone 1.0 mg/mL (TobraDex) 5 times daily for 2 weeks followed by dexamethasone 1.0 mg/mL 3 times daily for 2 weeks. Patients were examined 1 day, 1 week, and 1, 3, and 6 months after surgery. At each visit, refraction was performed and BCVA was measured using Snellen optotypes. The ECD and pachymetry were evaluated 1 week and 1, 3, and 6 months after surgery. The mean pachymetry and ECD values were calculated. Statistical analysis of the postoperative changes in pachymetry and endothelial cell count (ECC) between right eyes and left eyes in both groups was performed using the paired t test. All mean values are reported with their standard deviation. RESULTS The 56 patients were divided into 2 groups. The mean age in Group A (n = 28) (younger than 80 years) was 63 years (range 50 to 65 years). The mean age in Group B (n = 28) (80 years or older) was 83 years (range 80 to 93 years). Group B had a higher frequency of harder nuclei (Figure 1). No eye having NeoSoniX phacoemulsification had a cataract of grade 4. Phacoemulsification Parameters AquaLase Table 2A shows the median phacoemulsification values for AquaLase according to nuclear grade. The median AquaLase time was 0.3 seconds (range 0 to 4.3 seconds) in Group A and 0.9 seconds (range 0.1 to 3.8 seconds) in Group B. The number of pulses ranged from 0 (soft lens; only irrigation/aspiration using high vacuum was used) to 5280 (hard cataract, grade 4). The median number of pulses was 493 in Group A and 1410 in Group B. Fixed flow and vacuum were used in all cases, with a dynamic rise of 2 or 3 (Table 1A). The mean peak vacuum was 537 G 77 mm Hg (median 542 mm Hg; range 369 to 729 mm Hg) in Group A and 520 G 118 mm Hg (median 570 mm Hg; range 60 to 596 mm Hg) in Group B. NeoSoniX Table 2B shows the median phacoemulsification values for NeoSoniX according to nuclear grade. The median phaco power was 5.95% (range 0% to 16.5%) in Group A and 5.00% (range 2.0% to 21.0%) in Group B. The median effective phaco time was 7.2 seconds (range 0 to 16.1 seconds) in Group A and 7.0 seconds (range 1.3 to 22.6 seconds) in Group B. Fixed flow and vacuum were used in all cases, with a dynamic rise of 3 or 4 (Table 1B). The mean peak vacuum was 532 G 77 mm Hg (median 548 mm Hg; range 380 to 696 mm Hg) in Group A and 570 G 29 mm Hg J CATARACT REFRACT SURG - VOL 34, MARCH 2008 379 EFFECT OF AQUALASE AND NEOSONIX ON CORNEAL ENDOTHELIUM Table 1A. AquaLase settings by cataract grade. Cataract Grade 1 2 3 4 Linear Magnitude (% @ pps) Burst (%) 60 @ 40 80 @ 50 100 @ 50 100 @ 50 50 50 50 70 Fluidics (cm), Fixed Flow (cc/min), Fixed Vacuum (mm Hg) 96, 36, 500 100, 40, 550 105, 40, 600 105, 40, 650C Dynamic Rise 2 2 3 3 pps Z pulses per second (median 553 mm Hg; range 545 to 625 mm Hg) in Group B. Surgical Outcomes Figure 2 shows the mean ECC values and Figure 3 shows the mean pachymetry values in Group A and Group B preoperatively as well as 1 week and 1, 3, and 6 months postoperatively. In Group A, the differences in postoperative changes in ECC and pachymetry between the right eye (AquaLase) and left eye (NeoSoniX) were not statistically significant. In Group B, there were statistically significant differences in postoperative changes in ECC and pachymetry, with the results better in AquaLase eyes. Figure 4 shows the P value for ECC (A) and pachymetry (B) in both groups at each postoperative visit. The BCVA improved in all eyes immediately after surgery and remained stable during the entire follow-up (Figure 5). In Group B, 16 patients (57%) had incipient age-related macular degeneration, which was the cause of the worse results in this group. DISCUSSION The art and science of cataract removal by Kelman US phacoemulsification12,13 are continually evolving. Improvements in technique and technology have made the procedure safer and more efficient than in the past. Each surgeon should incorporate new developments to achieve the greatest possible benefit for patients. The Infiniti Vision System is the newest addition to Alcon’s line of phacoemulsification machines. It has various options for lens removal including traditional US, NeoSoniX, AquaLase, and torsional OZil. NeoSoniX was introduced as an upgrade to the Alcon Legacy; in addition to conventional US phacoemulsification, the NeoSoniX option adds oscillations up to 2 degrees at an approximate frequency of 100 Hz. The addition of oscillatory movement improves surgeon control and occlusion management and enhances cutting performance, allowing lower energy production, with a resultant lower risk for intraoperative damage, and providing better surgical outcomes.11,14 Rather than using mechanical US energy from a vibrating phaco needle, the AquaLase handpiece uses warm pulses of BSS to emulsify the lens material for aspiration.15,16 AquaLase potentially reduces the risk for damage to intraocular tissues because the fluid pulses are quickly dampened in the eye’s fluid environment. This effect rapidly diminishes elsewhere in the eye; thus, there is no radiating US pressure wave. The other fundamental difference between AquaLase and conventional US phacoemulsification is that there is no possibility of an incision burn from AquaLase. In conventional US lens removal, thermal tissue damage at the incision site is a potential complication with significant sequelae.17,18 The solution used by AquaLase is warmed to 57 C, and experimental measurement of internal wound temperature has shown that no incision heat is generated, even at full power.16 The softer AquaLase tip is more capsule friendly, and there is a decreased risk for posterior capsule rupture. We have been using the Infiniti Vision System since July 2004. Based on our experience, the learning curve for AquaLase is short for experienced US Table 1B. NeoSoniX settings by cataract grade. Cataract Grade 1 2 3 4 Fixed Burst (% for ms) NeoSoniX Amplitude (%) Fluidics (cm), Fixed Flow (cc/min), Fixed Vacuum (mm Hg) Dynamic Rise 25 for 50 30 for 20 50 for 20 70 for 80 50 60 70 80 60, 36, 400 90, 40, 550 90, 40, 600 100, 40, 650C 3 3 3 4 J CATARACT REFRACT SURG - VOL 34, MARCH 2008 380 EFFECT OF AQUALASE AND NEOSONIX ON CORNEAL ENDOTHELIUM 30 2,900 ECC (cells/mm2) 25 number of eyes group A AquaLase nuclear grade 1 nuclear grade 2 nuclear grade 3 nuclear grade 4 20 15 10 2,800 group A NeoSoniX 2,700 group B AquaLase group B NeoSoniX 2,600 2,500 2,400 2,300 2,200 5 2,100 2,000 0 group A preop groupB 1 week 1 month 3 months 6 months Figure 1. Comparison of the nuclear density between AquaLase and NeoSoniX. Figure 2. Comparison of mean ECC values between AquaLase and NeoSoniX preoperatively and postoperatively (ECC Z endothelial cell count). phacoemulsification surgeons. We routinely use the quick-chop technique19 with NeoSoniX or OZil. We found that AquaLase liquefaction is performed more efficiently with prechopping of the nucleus. We found that once the pieces are created, whether by grooving, chopping, or prechopping, it is best to remove them with as little tip motion as possible. This is achieved using fixed flow and fixed vacuum to optimize occlusion. In the present study, both AquaLase and NeoSoniX were safe and efficient methods of cataract removal. There was minimal loss of endothelial cells and changes in the corneal thickness after surgery in both eyes of patients in both groups. Statistically significantly less postoperative endothelial cell loss and pachymetry changes in elderly patients with harder nuclei and primary disabled endothelium after AquaLase cataract removal suggests this method is ‘‘friendly’’ to the corneal endothelium. Despite the longer AquaLase time and higher number of pulses, the results were better in eyes having AquaLase than in eyes having NeoSoniX. The only limitation of AquaLase we found is that it is not as effective as NeoSoniX or OZil in eyes with rock hard cataract (grade 5). The use of axial US energy coupled with oscillations of the tip with NeoSoniX appears more effective for these hard lenses. AquaLase easily extracts all cataracts of grade 1 and 2 and efficiently removes dense cataracts (grade 3 and many grade 4). For these reasons, eyes with black or brown mature cataract (grade 5) were not included in this study. One reason we believe AquaLase performed so well is the fluidics of the Infiniti Vision System. We were able to safely use high vacuums (400 to 650C mm Hg) and high flow rates (40 mL/min) with full occlusion of the aspiration port. We consider AquaLase a promising new technology. Because it is very difficult to rupture the posterior capsule using AquaLase, the device is excellent for polishing the capsule and removing lens epithelial cells. Although AquaLase is especially well suited to refractive lens procedures and pediatric cataract, extraction of hard and dense nuclei is also possible. Several studies20,21 have evaluated corneal endothelial cell injury during phacoemulsification with IOL implantation. Operative factors associated with endothelial cell loss include older age, total amount of US energy, high nucleus grade, greater infusion volume and turbulence of the irrigating solution, ricocheting of nuclear fragments, and IOL and/or instrument contact. Ophthalmic viscosurgical devices play an Table 2A. Median AquaLase values by cataract grade. Table 2B. Median NeoSoniX values by cataract grade. Median Cataract Grade 1 2 3 4 AquaLase Time (s) Number of Pulses Peak Vacuum (mm Hg) 0.09 0.35 0.70 2.60 126 490 1180 3440 468.5 544.0 592.0 536.0 Median Cataract Grade Median Phaco Power (%) Phaco Time (s) Peak Vacuum (mm Hg) 20.45 29.75 42.00 2.30 6.95 8.10 493.5 550.5 595.0 1 2 3 J CATARACT REFRACT SURG - VOL 34, MARCH 2008 381 EFFECT OF AQUALASE AND NEOSONIX ON CORNEAL ENDOTHELIUM 0.9 585 group A AquaLase group A NeoSoniX group B AquaLase group B NeoSoniX 580 0.8 0.7 570 mean BCVA PACHYMETRY (µ) 575 565 560 555 550 group A AquaLase group A NeoSoniX group B AquaLase group B NeoSoniX 0.6 0.5 0.4 0.3 0.2 545 0.1 540 0.0 535 preop 1 week 1 month 3 months 6 months preop 1 week 1 month 3 months 6 months Figure 3. Comparison of the pachymetry values between AquaLase and NeoSoniX preoperatively and postoperatively. Figure 5. Comparison of the mean BCVA values between AquaLase and NeoSoniX preoperatively and postoperatively. important role by protecting endothelial cells and maintaining space in the anterior chamber or capsular bag. Based on their physical properties, OVDs can be divided into 2 groups: high viscosity cohesive and low viscosity dispersive. Cohesive agents are good at maintaining space, while dispersive agents are retained better in the anterior chamber. In this study, dispersive Viscoat was used for capsulorhexis creation and cohesive Provisc for IOL insertion in all eyes to create the same conditions for phacoemulsification and allow comparison of the effect of the surgical method on the endothelial cell loss. 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