AquaLase VERSUS NeoSoniX – A COMPARISON STUDY

AIMS
To compare the metrics and surgical outcome when using Infiniti AquaLase and NeoSoniX cataract removal modalities.


METHODS
This prospective clinical study involved 50 patients with bilateral cataracts and lens removal using AquaLase in the right eye and NeoSoniX in the left eye. Best corrected visual acuity (BCVA), endothelial cell density and pachymetry were evaluted pre- and postoperatively. Statistical analysis was performed using the Wilcoxon Signed- Rank Test.


RESULTS
Preoperative mean pachymetry was 569 +/- 31 mu in the right eye (RE) and 560 +/- 37 mu in the left eye (LE), mean endothelial cell density 2744 +/- 418 cells/mm(2) (RE) and 2730 +/- 472 cells/mm(2) (LE). One week after operation pachymetry was 576 +/- 52 mu (RE) and 583 +/- 72 mu (LE) and endothelial cell density 2388 +/- 586 cells/mm(2) (RE) and 2463 +/- 615 cells/mm(2) (LE). One month after surgery pachymetry was 556 +/- 43 mu (RE) and 559 +/- 44 mu (LE) and endothelial cell density 2368 +/- 52 cells/mm(2) (RE) and 2495 +/- 548 cells/mm(2) (LE). BCVA improved in all eyes and was 0.8 or better on the first postoperative day.


CONCLUSIONS
Both the NeosoniX and AquaLase minimize intraoperative damage to ocular structures.

Conventional ultrasonic (US) phacoemulsifi cation is created in a handpiece when power is applied to piezoelectric crystals which convert the electrical energy into mechanical vibrations of the phaco needle.The phaco needle tip is used to emulsify the lens material at ultrasonic frequencies generally between 25 KHz and 62 KHz, which creates both thermal and cavitational energy with potential damage to the cornea.NeoSoniX handpiece delivers oscillatory sonic and axial ultrasonic 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 produces no signifi cant thermal energy and thus minimizes the risk for thermal injury.Previous studies 11 suggest that US coupled with oscillatory motion is more effi cient than just applying axial energy alone.
The AquaLase liquefaction device is one of the most recent innovations in phacoemulsifi cation.Warmed pulses (57 °C) of balanced salt solution (BSS) are used to strain and dissolve the lens for aspiration.Within the AquaLase handpiece, 4 μL fl uid 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 fl uid 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 liquefi ed 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 foot-pedal depression.
The purpose of this study was to compare the metrics and surgical outcome using AquaLase and NeoSoniX cataract removal modalities.

MATERIALS AND METHODS
This prospective clinical study included 50 patients with bilateral lens opacifi cation scheduled for cataract surgery at the Department of Ophthalmology, University Hospital, Hradec Králové.Patients were selected from the waiting list.To be eligible for the study, both eyes had to have cataract preferably with similar grades of density.Patients with ocular surface disease, endothelial or stromal corneal dystrophies as well as corneal scars, macular degeneration or any conditions that would aff ect postop-erative visual recovery were excluded.The purpose, procedures, and responsibilities were explained to all potential participant, and informed consent was obtained.
Before surgery, a complete eye examination was performed.Best corrected distance visual acuity was measured using Snellen optotypes, endothelial cell density and pachymetry using specular microscope CONAN NONCON ROBO.Cataracts were graded clinically on the basis of their hardness according to the Buratto classification 2 (grade 1-5 scale).Patients with very hard nucleus (grade 5 -brown or black hard-rock cataracts) were not included in this study.Surgery was performed by two surgeons (NJ, PR), one surgeon per patient (both eyes).Phacoemulsifi cation was performed under topical anesthesia via 3.0 mm limbal incision using AquaLase in the right eye and NeoSoniX in the left eye.The standard AquaLase soft polymer needle (fl ared at the tip) with a 1.1 inner diameter and a 1.32 mm outer diameter was used in the case of AquaLase procedures and a 30-degree round 1.1 mm fl ared ABS tip in the cases of NeoSoniX use.The phaco settings were modifi ed for each cataract grade on both lens removal modalities (Table 1 and 2).AcrySof Single Piece IOLs (Alcon) were implanted in the bag through a Monarch II injector system.All patients received topical tobramycin 3.0 mg /mL and dexamethasone 1.0 mg/mL (Tobradex ® ) fi ve times daily for 2 weeks postoperatively, followed by dexamethasone 1,0 mg/mL (Dexamethason ® ) three times daily for 2 weeks.
Best corrected Snellen visual acuity at a distance was measured on the fi rst postoperative day, 1 week and 1 month after surgery.Endothelial cell density and pachymetry were evaluated 1 week and 1 month after surgery.The mean values of pachymetry and endotellial cell density were calculated, as well as standard deviation (SD) of the means in each group.Statistical analysis of the postoperative changes of pachymetry (diff erence between the postoperative and preoperative values) and ECC (diff erence between the preoperative and postoperative values) was performed using the Wilcoxon Signed-Rank Test, which compares, pair by pair, the rank values of the selected variables, and displays the count of positive and negative diff erences.

Phacoemulsifi cations Metrics
The mean AquaLase time was 1.04 ± 1.16 seconds.Number of pulses varied from 0 (soft lens where only irigation/aspiration using high vacuum was employed) to 5280 (hard cataract grade 4).The median value was 975 pulses, the mean value was 1353 ± 1407 pulses.Fixed fl ow and vacuum were used in all AquaLase cases, the dynamic rise was chosen 2 or 3 (Table 1).The peak vaccum varied from 141 mmHg to 729 mmHg, median 545, mean 520 ± 95 mm Hg.
In the NeoSoniX phacoemulsifications the mean phaco power was 6.9 ± 4.7 % and the mean eff ective phaco time was 7.14 ± 5.8 seconds.Fixed fl ow and vacuum were used in all eyes and the dynamic rise was 3 or 4 (table 2).The peak vacuum varied from 380 to 696 mmHg, median 549.5, mean 545.7 ± 62.1 mmHg.

DISCUSSION
The art and science of cataract removal through Kelman ultrasonic phacoemulsifi cation 12,13 is constantly evolving -continual improvements in phaco technique and technology have made the procedure more safe and effi cient than was possible in the past.Surgeons need to encorporate new developments to achieve the greatest possible patient benefi t.
The Infi niti Vision System (Alcon Laboratories, Fort Woth, Texas) is the newest addition to the Alcon line of phacoemulsifi cation instruments.It off ers various options for lens removal, including traditional ultrasound, NeoSoniX and AquaLase.NeoSoniX was originally introduced as an upgrade of the Alcon Legacy and in addition to conventional US phacoemulsifi cation, the NeoSoniX option adds oscillations up to 2 degrees at an approximate frequency 100 Hz.The addition of oscillattory movement improves surgeon control and occlusion management, enhances cutting performance, allowing lower energy production with resultant lower risk of intraoperative damage and better surgical outcomes 11,14 .
Rather than using mechanical US energy from a vibrating phaco needle, the AquaLase handpiece uses warmed pulses of balanced salt solution (BSS) to emulsify the lens material for aspiration 15,16 .AquaLase off ers the advantage of potentially reducing the risk of damage to intraocular tissues because the fl uid pulses are quickly dampened in the eye's fl uid environment.The attenuation eff ect very rapidly spreads elsewhere in the eye -there is no radiating ultrasonic pressure wave.The other fundamental diff erence between AquaLase and conventional US phacoemusifi cation is that there is no possibility of incision burn from AquaLase.In conventional US lens removal, thermal tissue damage at the incision site is a potential complication with signifi cant sequellae 17,18 .The solution used by AquaLase is warmed to 57°C, and experimental measurement of internal wound temparature has shown that no incision heat is generated even at full power 16 .The softer AquaLase tip is more capsule friendly and there is decreased risk of rupture of the posterior capsule.In this limited series we have not seen any of this intraoperative complication.
We have been using the Infi niti Vision System since July 2004.We now routinely use only NeoSoniX or AquaLase in 100 % of our cases.Based on our own experience, there is a short learning curve for the experienced US phacoemulsifi cation surgeon in adopting AquaLase.We perform routinely quick-chop technique when using NeoSoniX.We have found that AquaLase liquefaction is performed more effi ciently with prechopping of the nucleus.Once the pieces are created -whether by grooving, chopping or prechopping, we found it benefi cial to remove them with as little motion of the tip as possible.This was achieved by using fi xed fl ow and fi xed vacuum to optimize occlusion.
Both AquaLase and NeoSoniX proved to be safe and effi cient for cataract removal in our survey.There was minimal change in corneal thickness after surgery with the results slightly better in the AquLase group.There was no signifi cant loss of the endothelial cells in either groups.
The only limitation of AquaLase that we have found is that it is not as eff ective as NeoSoniX in the case of harder cataracts (grade 4 and 5).With these harder lenses, the NeoSoniX use of axial US energy coupled with oscillations of the tip appears more eff ective.AquaLase easily extracts all cataracts of grade 1 and 2. With prechopping of the nucleus, AquaLase is also able to effi ciently remove dense cataracts of grade 3 and many of grade 4. For those cases, where lens density was too hard for effi cient AquaLase use, we were able to easily transition to the NeoSoniX handpiece with minimal eff ort.
One of the reasons we suspect that AquaLase is so successful is through the impressive fl uidics of the Infi niti Vison System.We found we were able to safely use high vacuums (400 to 650+ mm Hg) and high flow rates (40 mL/min) with full occlusion of the aspiration port.
The AquaLase is one of the most promising new technologies available today and the techniques for its use are still evolving.Because it is exceedingly diffi cult to rupture the posterior capsule while using AquaLase, this modality is excellent for polishing the capsule and removing lens epitelial cells.AquaLase is especially well suited to refractive lens procedures and pediatric cataracts.With prechopping of the nucleus we now use AquaLase in 60-70 % of our cataract cases in which we are removing even hard and dense nuclei.

CONCLUSUION
In conclusion, the results of our bilateral 50 patient study demonstrated that both Infiniti AquaLase and NeoSoniX modalitis using the Infiniti Vision System provided similar high-quality post-operative results There was a statistical signifi cant diff erence in the postoperative changes for pachymetry with better results in AquaLase group using the Wilcoxon Signed-Rank Test one month later.The inherent design of AquaLase essentially eliminates the possibility of wound site thermal injury.The softer tip is more capsule friendly.Since our study appears to show that AquaLase provides similar and perhaps slightly improved outcomes, it is a method we try to use on all cataracts of grades 1-3.We believe this new techology minimizes intraoperative damage to ocular structures and maximizes the level and rapidity of visual rehabilitation.

Fig. 1 .
Fig. 1.Mean pachymetry values and standard deviations in AquaLase and NeoSoniX groups preoperatively, 1 week and 1 month after operation.At one month follow-up there was a statistically signifi cant diff erence between both groups in the postoperative changes (diff erence between postoperative and preoperative values) *.

Fig. 2 .
Fig. 2. Mean endothelial cell density values and standard deviations in AquaLase and NeoSoniX groups preoperativelly, 1 week and 1 month after operation

Table 1 .
AquaLase settings for each cataract grade

Table 2 .
NeoSoniX settings for each cataract grade.

Table 3 .
Status of the cornea on the fi rst postoperative day in AquaLase and NeoSonix groups.