Purpose
To compare the safety and efficacy of microcoaxial phacoemulsification surgeries performed with the OZil Intelligent Phaco torsional mode (Alcon Laboratories, Inc., Fort Worth, USA) and combined torsional/longitudinal ultrasound mode using 45 degree aperture angled tips.
Design
Prospective randomized clinical trial.
Methods
setting : Maltepe University, Istanbul. patient population : Eighty eyes of 80 cataract patients were randomly assigned to 2.2 mm microcoaxial phacoemulsification using the OZil Intelligent Phaco torsional mode (Group 1) or combined torsional/longitudinal ultrasound mode (Group 2). observation procedure : Intraoperative fluid and energy usage and postoperative examinations were evaluated. main outcome measures : Ultrasound time, cumulative dissipated energy, longitudinal and torsional ultrasound amplitudes, mean operation time, mean volume of fluid used, and surgical complications.
Results
Both groups included 40 eyes. Mean ultrasound time, cumulative dissipated energy, and longitudinal and torsional ultrasound amplitudes in Group 1 were 58.21 ± 33.81 seconds, 7.74 ± 6.23, 0.45 ± 0.30, and 26.30 ± 12.60%, respectively, and these parameters in Group 2 were 64.75 ± 30.23 seconds, 12.61 ± 6.21, 26.32 ± 5.85, and 40.98 ± 8.33%, respectively. Cumulative dissipated energy and longitudinal and torsional amplitudes were found to be significantly lower in Group 1 ( P = .001, P < .001, P < .001). Mean volumes of fluid used in Groups 1 and 2 were 73.30 ± 19.87 cc and 107.07 ± 21.82 cc, respectively ( P < .001).
Conclusion
With the aid of a 45 degree aperture angled tip, the OZil Intelligent Phaco torsional mode provided more effective lens removal than the combined torsional/longitudinal ultrasound mode, with a lower cumulative dissipated energy and volume of fluid used.
Phacoemulsification has allowed surgeons to perform cataract operations using very small corneal incisions. The energy needed to emulsify the lens material is transferred by the ultrasonically vibrating tip. Although this energy is delivered efficiently to the nucleus owing to recent advances in techniques and technologies, it still carries some risk of injury to the delicate ocular structures, such as the corneal endothelium, especially in hard cataracts.
Conventional longitudinal phacoemulsification occurs by the forward and backward movement of the tip. The energy is delivered directly to the nucleus by the forward movement of the tip, which is also called the active part of the cycle. However, the same energy is also delivered to the eye during the backward movement. This passive part of the cycle creates no effective cutting, but friction and heat production still continues. The forward kick could also cause repulsion of the lens material, especially if the vacuum is not strong enough to hold the fragments.
To increase the efficiency of the ultrasonic emulsification, a new energy delivery system, called torsional phaco, was developed in January 2006 when Alcon Surgical incorporated OZil torsional into the Infiniti Vision System (Alcon Laboratories, Inc., Fort Worth, USA). Unlike conventional longitudinal phacoemulsification, which emulsifies the lens with forward and backward movements of the phaco tip, OZil torsional technology produces a side-to-side motion of the phaco tip. Efficiency is increased with this technology because it does not produce repulsion; instead, it breaks up the nucleus by shearing and not by the conventional jackhammer effect. Because clogging decreases the efficiency of torsional ultrasound by inducing the loss of the optical shearing plane, the Intelligent Phaco upgrade, which delivers a very small amount (short pulse) of longitudinal ultrasound just after reaching the preset maximum vacuum level, was added to the OZil torsional technology to further increase its efficiency. Tip anatomy is a very important determinant for energy delivery efficiency. Therefore, we designed a study to analyze the behavior of a 22 degree bent tip with a 45 degree aperture angle and to compare the intraoperative and short-term outcomes of phacoemulsification using the OZil Intelligent Phaco torsional mode with the combined torsional/longitudinal ultrasound mode.
Methods
This prospective randomized comparative study was conducted at the Maltepe University and Basaksehir State Hospital Ophthalmology Departments from June 1, 2012 to December 30, 2012. Eighty eyes of 80 patients who attended our clinic with the diagnosis of cataract were enrolled in the study. Patients were excluded if they had other ocular or systemic disease that could affect their vision. Patients with significant pseudoexfoliation or using medications with a high risk of intraoperative floppy iris syndrome were also excluded. After providing informed consent, patients with similar nucleus density grades were randomly distributed to the surgery groups. The study was in adherence with the tenets of the Declaration of Helsinki, and the Institutional Review Board (Maltepe University Ethics Committee for Clinical Researches) approved this prospectively designed study. A block randomization method was used to equalize the sample sizes in both groups.
Routine preoperative examinations were performed. The Lens Opacities Classification System II (LOCS II) was used for nucleus grading. Equal numbers of eyes were distributed into the groups for each nucleus density grade. All of the procedures were performed by experienced surgeons (F.H. and C.Y.). A standard quick-chop technique was used with the Infiniti Vision System in the OZil Intelligent Phaco torsional mode and the combined torsional/longitudinal ultrasound mode. A 0.9 mm 45 degree mini-flared 22 degree bent tip was used in all of the operations. The holding surface of the 45 degree tip was 0.68 mm 2 . The outer and inner diameters of the port were 0.91 and 0.81 mm, respectively. The outer and inner diameters of the shaft were 0.82 and 0.57 mm, respectively. For the torsional Intelligent Phaco mode, the torsional continual model with an 80% amplitude was selected. The Intelligent Phaco pulse was set at 70% of the longitudinal torsional ratio. The Intelligent Phaco vacuum threshold was 95% of the maximum vacuum, and the pulse length was 10 ms. For the combined torsional/longitudinal ultrasound mode, the maximum longitudinal and torsional ultrasound amplitudes were set at 40% and 60%, respectively. The pulse frequency was 10 pulses per second, and the duty cycles of the longitudinal and torsional ultrasound were 35% and 65%, respectively. The fluid settings were the same for both groups. The bottle height was set at 100 cm, aspiration was 32 cc/min, maximum vacuum was 330 mmHg, and dynamic rise was 1.
All patients received peribulbar anesthesia with 4 mL of 0.125 mg/mL epinephrine and 2 g/mL lidocaine (Jetocaine; Adeka, Co., Ltd, Istanbul, Turkey) before surgery. A 2.2 mm self-sealing limbal incision was made by the intrepid ClearCut 2.2 mm dual-bevel metal keratome (Alcon Laboratories, Inc., Fort Worth, USA) on the steep axis. Sodium hyaluronate 3.0% and sodium chondroitin sulfate 4.0% (Viscoat; Alcon Laboratories, Inc., Fort Worth, USA) were used to reform the anterior chamber and to protect the corneal endothelium. A 5.5- to 6-mm continuous curvilinear capsulorrhexis was created with a 26 gauge needle. Trypan blue 0.4% (Rhex ID; Appasamy Associates , Chennai, India) was used to improve the visualization of the capsule in cases with dense cataracts. A hydrophilic acrylic intraocular lens was inserted with the injector system through a 2.2 mm incision into the bag. The wound was sealed by stromal hydration.
The primary outcome measures were the ultrasound time, cumulative dissipated energy, longitudinal and torsional ultrasound amplitudes, mean operation time, mean volume of balanced salt solution used, and surgical complications. Patients were seen 1, 7, and 30 days after surgery. The postoperative outcome measures were the anterior chamber reactions, change in corneal clarity, central corneal thickness, and final best-corrected visual acuity. The levels of inflammation and corneal edema 1 day post operation were evaluated on a subjective 4-point scale ( Table 1 ). The central corneal thickness was also measured on the first day postoperatively using a Nidek Ultrasound-4000 combined A-B scan ultrasound and pachymeter (Nidek devices; Nidek Co., Ltd, Japan). The preoperative keratometry measurements and postoperative first month best-corrected visual acuity measurements were performed using a Nidek Tonoref II (Nidek).
| Grade | Severity | Anterior Chamber Reaction | Postoperative Corneal Edema |
|---|---|---|---|
| Grade 0 | None | No cells or flare | No Descemet striae or epithelial edema |
| Grade 1 | Mild | 1–3 cells per 16 × beam field | Subtle Descemet striae or edema around the incision |
| Grade 2 | Moderate | 3–10 cells per 16 × beam field | Obvious Descemet striae or wound edema; patchy epithelial edema still allowing good visualization of the iris detail |
| Grade 3 | Severe | More than 10 cells per 16 × beam field | Obvious Descemet striae and wound edema; diffuse epithelial edema not allowing good visualization of the iris detail |
SPSS 12.0 software was used for the statistical analyses. Paired-samples and independent-samples t tests were used to test the differences in the ultrasound time, cumulative dissipated energy, ultrasound amplitudes, mean operation times, mean volume of balanced salt solution used, central corneal thickness changes, and best-corrected visual acuity measurements. The χ 2 test was used to compare the nucleus density grades, corneal edema, and anterior chamber reaction grades. A P < .05 was considered statistically significant.
Results
A total of 80 eyes (80 patients) were enrolled in the study and divided into 2 groups. Both groups had 40 eyes (40 patients). The mean patient age was similar in the OZil Intelligent Phaco torsional mode group (Group 1) and the combined torsional/longitudinal ultrasound mode group (Group 2) ( P = .697).
The demographic data of the patients in both groups showed similar distributions ( Table 2 ). The χ 2 test showed the distributions of the sex and the operated eyes of the patients were similar in both groups ( P = .485, P = .499). The mean nucleus grade in both groups was 2.80 ± 1.01.
| Groups | Sex Distribution | Operated Eyes | Mean (±SD) Age (y) |
|---|---|---|---|
| Group 1 a (N = 40) | 24 male (60%) | 16 right (40%) | 68.32 ± 7.77 |
| Group 2 b (N = 40) | 27 male (67.5%) | 19 right (47.5%) | 68.62 ± 8.41 |
| P value | .485 | .499 | .869 |
a Group 1: 2.2 mm phacoemulsification surgeries performed by the OZil Intelligent Phaco torsional mode.
b Group 2: 2.2 mm phacoemulsification surgeries performed by the combined torsional/longitudinal ultrasound mode.
In the analyses of the surgical outcomes of the groups, the mean ultrasound time was found to be similar, whereas the mean cumulative dissipated energy and longitudinal and torsional amplitudes and volumes of the balanced salt solution used were found to be significantly lower in Group 1 ( Table 3 ) ( P = .364, P = .001, P < .001, P < .001, P < .001, respectively). The mean operation time was also found to be significantly lower in Group 1 ( P = .019). No intraoperative complications were observed in any of the patients.
| Groups | Ultrasound Time | Cumulative Dissipated Energy | Longitudinal Ultrasound Amplitude | Torsional Ultrasound Amplitude | Mean Operation Time | Mean Volume of Balanced Salt Solution |
|---|---|---|---|---|---|---|
| Group 1 a | 58.21 ± 33.81 s | 7.74 ± 6.23 | 0.45 ± 0.30 | 26.30 ± 12.60% | 888.37 ± 165.25 s | 73.30 ± 19.87 cc |
| Group 2 b | 64.75 ± 30.23 s | 12.61 ± 6.21 | 26.32 ± 5.85 | 40.98 ± 8.33% | 1083.63 ± 501.48 s | 107.07 ± 21.82 cc |
| P value | P = .364 | P = .001 | P < .001 | P < .001 | P = .019 | P < .001 |
a Group 1: 2.2 mm phacoemulsification surgeries performed by the OZil Intelligent Phaco torsional mode.
b Group 2: 2.2 mm phacoemulsification surgeries performed by the combined torsional/longitudinal ultrasound mode.
A biomicroscopic evaluation of the postoperative anterior chamber reactions and postoperative corneal edema showed mild changes in both groups. The mean anterior chamber reactions in Groups 1 and 2 were 0.30 ± 0.46 and 0.62 ± 0.66, respectively ( P = .013). The mean corneal clarity changes in Groups 1 and 2 were 0.37 ± 0.58 and 0.70 ± 0.64, respectively ( P = .021). A significantly reduced reaction and significantly reduced corneal clarity changes were observed in Group 1.
Postoperative first-day corneal thickness measurements revealed an increase in both groups. Significantly reduced central corneal thickness changes were observed in Group 1 ( P < .001). No postoperative complications such as synechiae, fibrin formation, or endophthalmitis were observed in any of the patients in the short-term follow-up period.
At 30 days, the mean best-corrected visual acuity values were 0.01 ± 1.30 logMAR in Group 1 and 0.04 ± 1 logMAR in Group 2 ( P = .001). Significantly better visual acuities were observed in Group 1 than in Group 2 in terms of the final best-corrected visual acuity measurements.
The groups were further divided into 4 subgroups according to the nucleus density grades ( Table 4 ). Although less ultrasound time was used in Group 1 for all densities, statistical significance was observed only for the Grade 1 subgroups ( P = .013). The cumulative dissipated energy was significantly lower in Group 1 for all the density grades (grade 1, P = .004; grade 2, P < .001; grade 3, P < .001; grade 4, P = .002). The mean volume of balanced salt solution used was significantly lower in Group 1 for all the density grades (grade 1, P = .003; grade 2, P < .001; grade 3, P < .001; grade 4, P = .001). The mean central corneal thickness change was lower in Group 1 for all densities and was statistically significant for grade 1, grade 3, and grade 4 densities (grade 1, P = .003; grade 2, P = .072; grade 3, P = .001; grade 4, P < .001).
