Biaxial microincision versus coaxial small-incision cataract surgery in complicated cases

ARTICLE

Biaxial microincision versus coaxial small-incision cataract surgery in complicated cases Sabine Kurz, MD, Frank Krummenauer, PhD, Hagen Thieme, MD, H. Burkhard Dick, MD

PURPOSE: To evaluate and compare the results of biaxial microincision and coaxial small-incision surgery in patients with cataract with coexisting exfoliation syndrome, uveitis, anterior or posterior synechias, phacodonesis, or previous intraocular surgery over an 8-week follow-up. SETTING: Department of Ophthalmology, Mainz University, Mainz, Germany. METHODS: Eyes were prospectively assigned (1:1) to have biaxial microincision (<1.5 mm) phacoemulsification or coaxial small-incision (2.8 mm) phacoemulsification using pulsed ultrasound energy (Sovereign WhiteStar) with variable duty cycles followed by implantation of a microincision intraocular lens. Intraoperative and postoperative complications, corrected distance visual acuity (CDVA), laser flare photometry values, effective phacoemulsification time (EPT), and endothelial cell count (ECC) were evaluated. RESULTS: The study enrolled 94 eyes. There were no statistically significant differences between the techniques in intraoperative or postoperative complications. The most frequent postoperative complications were corneal edema surrounding the incision (40%, biaxial group; 35%, coaxial group), pupil distortion (3% versus 7%), and fibrin exudation (3% versus 3%). No other postoperative complications occurred. The median EPT was statistically significantly shorter (1.34 seconds versus 5.4 seconds) and the median phaco power significantly lower (3.3% versus 12.9%) in the biaxial group than in the coaxial group (P<.001). There were no differences between groups in CDVA, laser flare photometry values, or ECC. CONCLUSIONS: The EPT was shorter and the mean phaco power lower with biaxial phacoemulsification, perhaps because of better access of the phaco handpiece for grooving the nucleus with this technique. The 2 techniques were comparable in intraoperative and postoperative complications. Financial Disclosure: No other author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2010; 36:66–72 Q 2010 ASCRS and ESCRS

Biaxial microincision clear corneal cataract surgery has gained increasing interest by cataract surgeons during the past few years. The method, which was first described by Shearing et al.1 in 1985, uses a smaller incision than previous techniques. Unlike conventional coaxial phacoemulsification, biaxial phacoemulsification uses a separate irrigation instrument and a sleeveless phaco tip to remove the cataractous lens. Irrigation during phacoemulsification is through a separate irrigating chopper instead of through the phaco handpiece. The chopper provides irrigation to the anterior chamber, and the phaco handpiece acts as a bare needle without a sleeve to emulsify and aspirate the nuclear fragments. Thus, biaxial phacoemulsification can be performed through an incision smaller than 1.5 mm. The goal of this study was to evaluate the short-term and intermediate outcomes of biaxial microincision 66

Q 2010 ASCRS and ESCRS Published by Elsevier Inc.

phacoemulsification versus coaxial small-incision phacoemulsification in complicated cases. The main outcome measures were intraoperative and postoperative complications, visual acuity, laser flare photometry values, and endothelial cell loss. PATIENTS AND METHODS This prospective clinical trial included patients admitted for elective unilateral cataract surgery and intraocular lens (IOL) implantation. An independent local ethical board committee approved the clinical trial before the start of the study. All patients provided written informed consent before inclusion in the study. The patients were randomly assigned (1:1 block randomization) to have biaxial microincision phacoemulsification or conventional coaxial phacoemulsification. All eyes were difficult cases based on an increased risk for intraoperative or postoperative complications, which was determined at the 0886-3350/10/$dsee front matter doi:10.1016/j.jcrs.2009.07.036

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preoperative examination. Preoperatively, all patients had a complete medical history and ophthalmologic examination to establish potential suitability for participation in the study. Figure 1 shows the inclusion criteria for the study. The exclusion criteria were (1) low lens opacification (%grade 3) on the Lens Opacities Classification System III (LOCS)2 opalescence scale and an otherwise healthy eye and (2) poor compliance.

Surgical Technique On the day of surgery, the pupil was dilated with 1 drop each of tropicamide 0.5% and phenylephrine 0.5%. One drop of diclofenac was applied during the time of pupil dilation. All patients had retrobulbar anesthesia and lid block injections (bupivacaine 0.5% and lidocaine 2%). The same surgeon (H.B.D.), who was experienced in biaxial and coaxial phacoemulsification, performed all surgeries. For both techniques, the same surgical equipment was used and pulsed ultrasound energy was applied.

Biaxial Microincision Phacoemulsification A 1-step 1.5 mm corneal incision was created parallel to the limbus with the front of a trapezoid steel keratome (Nanoedge, Geuder AG). The incision was at the 11 o’clock position. A second 1.0 mm incision was made at the 2 o’clock position for the irrigation sleeve. The anterior chamber was filled with sodium hyaluronate 1% (Healon). After a continuous curvilinear capsulorhexis was created with a 24-gauge self-bent needle, hydrodissection and hydrodelineation were performed. Using his right hand, the surgeon inserted a Teflon-coated 20-gauge phaco needle (Abbott Medical Optics, Inc.) through the 11 o’clock incision. Using his left hand, the surgeon inserted a Dick 19-gauge irrigating chopper (Geuder AG) with 2 irrigation ports to the side in the 2 o’clock incision.

Coaxial Phacoemulsification A 2-step 2.75 mm clear corneal tunnel incision was created at the 12 o’clock position with a clear corneal diamond keratome. Two 1.0 mm paracenteses were made with a steel keratome at the 10 o’clock and 2 o’clock positions. The anterior chamber was filled with an ophthalmic viscosurgical device (OVD). Capsulorhexis, hydrodissection, and hydrodelineation were performed as in biaxial microincision phacoemulsification. For phacoemulsification, a 19-gauge phaco needle (Abbott Medical Optics, Inc.) with a sleeve and 2 side ports for irrigation was inserted through the clear corneal tunnel. A second instrument (Neuhann manual chopper, Geuder AG) was inserted through the paracentesis at the 2 o’clock position.

Submitted: March 12, 2009. Final revision submitted: July 15, 2009. Accepted: July 15, 2009. From the Departments of Ophthalmology, Johannes GutenbergUniversity (Kurz, Thieme), Mainz, and Ruhr University (Dick), Bochum, and the Clinical Epidemiology and Health Economy Unit (Krummenauer), Dresden University of Technology, Dresden, Germany. Corresponding author: Sabine Kurz, MD, Department of Ophthalmology, Johannes Gutenberg-University, Langenbeckstrasse 1, 55101 Mainz, Germany. E-mail: [email protected].

Figure 1. Inclusion criteria (LOCS Z Lens Opacities Classification System).

Both Techniques The Koch and Katzin3 stop-and-chop technique was used to groove the nucleus. The following settings were used with a Sovereign phaco machine (WhiteStar, version 6 software, Abbott Medical Optics, Inc.): maximum phaco power 55%, bottle height 57 cm, aspiration rate 29 cc/min, and maximum vacuum 50 mm Hg. For emulsification and aspiration of the nucleus, the following settings were used: maximum phaco power 40%, bottle height 76 cm, aspiration rate 30 cc/min, and maximum vacuum 300 mm Hg. Pulsed phaco energy was used with a duty cycle (percentage time of active ultrasound per second) of 33% (equivalent to pulse rate of 1:2) and an irrigation pressure of 58 cc/min. Residual cortex removal and posterior capsule polishing were performed using bimanual irrigation/aspiration through the nasal and temporal incisions. The anterior chamber and capsular bag were reinflated with an OVD. An aspheric acrylic microincision IOL with an overall length of 11.0 mm and a 6.0 mm optic (36 A, Acri.Tec/Carl Zeiss Meditec) was implanted in the capsular bag using an injector (Acri-Shooter A1-4205, Acri.Tec GmbH). In the biaxial

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group, the microincision was enlarged from 1.5 mm to 1.7 mm for IOL implantation; the incision was not enlarged in the coaxial group. The OVD was removed and replaced with a balanced salt solution. All incisions were left sutureless. At the end of the procedure, the wounds were checked for leakage and found to be watertight. The effective phaco time (EPT) (applied pulsed ultrasound time in seconds after conversion to 100% phaco power) and the phaco power were recorded for each surgery. At the end of the operation, complications were documented. The surgeon rated the degree of surgical difficulty on a scale of 1 to 5 (very easy to very difficult). The day after surgery, all patients received topical prednisolone-21-acetate, with the dose according to individual circumstances. They also received gentamicin drops 3 times a day.

Clinical Examinations The same examiner performed all preoperative and postoperative examinations. The preoperative examination included slitlamp evaluation (anterior and posterior segment, intraocular pressure [IOP]), corrected distance visual acuity (CDVA), visual acuity measurement with a laser interference retinometer, axial length and anterior chamber depth measurement by optical biometry (IOLMaster, Carl Zeiss Meditec), and astigmatism evaluation by corneal topography (Technomed C-Scan). In addition, the endothelial cell count (ECC) was determined by noncontact specular microscopy (Endothelial Analysis System, Rhine-Tec) and aqueous flare was quantified by laser flare photometry (FM-500, Kowa). One day after surgery, patients were asked to assess intraoperative pain on a scale of 1 to 5 (no pain to very painful) and operative stress on a scale of 1 to 3 (no stress to very stressful). The CDVA, IOP, and laser flare values were determined at 1, 3, and 7 days. Postoperative complications were documented at each visit. Eight weeks postoperatively, the CDVA was measured and the ECC and astigmatism were determined by C-scan topography (central 0.0 to 3.0 mm zone).

Table 1. Criteria for preoperative diagnosis of complicated eye. Criterion Pseudoexfoliation syndrome Pupil diameter %5.0 mm Preexisting zonulysis Lentodonesis Previous corneal perforation Posterior synechias (total) Circular posterior synechias Previous vitrectomy Previous trabeculectomy Previous iridotomy Relevant corneal scars Corneal guttae Mature cataract Traumatic cataract Myopia O26.0 D Hyperopia !21.5 D Deep-set eye Shallow anterior chamber

Eyes (n) 17 25 12 16 2 13 7 8 12 8 2 11 4 2 8 13 2 9

nonparametric box whisker plots. For significance comparisons in continuous repeated measurements, the sign test was applied and the 2-sample Wilcoxon test used for group comparisons along continuous endpoints. For statistical analysis, logMAR visual acuity was converted to decimal notation and vice versa as described by Westheimer.4 Results of significance tests were summarized by P values. Evaluation of the primary clinical endpoint was by a 2-sample Wilcoxon test at a significance level of 5%; P values derived by analysis of secondary endpoints were not adjusted for multiplicity and, therefore, indicated local statistical significance when P!.05.

RESULTS

Statistical Analysis

Preoperative Patient Data

The primary clinical endpoints of the study, which determined the study sample size, were identification of statistically significant differences between treatment groups in intraoperative and postoperative complications. Patients were randomized 1:1 to the 2 treatment groups without stratification for putative confounders; random numbers were generated by an independent biometrician (F.K.) using SPSS software for Windows (version 10.0, SPSS, Inc.). A sample size of 47 was chosen to achieve a statistical power of 80% or more for the group comparison along with the study’s primary clinical endpoint using a 2-sample Wilcoxon test at a 5% significance level. This confirmatory test was determined to detect a clinically relevant intergroup difference in the primary clinical endpoint based on the required statistical power of 80% at the 5% significance level. The same biometrician performed all numerical and graphic evaluations using SPSS software for Windows (version 13.0). Data description was based on medians and quartiles for continuous endpoints and on absolute and relative frequencies for categorical endpoints. Comparisons of repeated measurements in continuous endpoints were evaluated using intraindividual differences and ratios. The graphic representation of continuous data was based on

Ninety-four eyes (94 patients) were enrolled in the study. There were 47 eyes in each group. Table 1 shows the criteria for preoperative diagnosis of complicated eye. Some patients had more than 1 criterion. A pupil smaller than 0.5 mm and pseudoexfoliation were the most common conditions. Table 2 shows the preoperative and intraoperative parameters. There was no statistically significant difference between the biaxial group and coaxial group in any parameter. Table 3 shows the distribution of preoperative lens opacification. The most common opacification was LOCS III grade 3 (69% biaxial group, 56% coaxial group). There was no statistically significant difference between the groups in lens opacity grade. Difficulty of Surgery and Patient Ratings The surgeon rated the biaxial procedure as very easy to easy in 2 cases (6%), medium in 9 cases (26%), and

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Table 2. Preoperative and intraoperative parameters.

Table 3. Distribution of preoperative lens opacification using slitlamp biomicroscopy (LOCS2) and objective quantification using the lens opacity meter.

Group Parameter Sex, n (%) Female Male Age (y) Median Range CDVA Median Range SE (D) Median Range Visual acuity (retinometer) Median Range Axial length (mm) Median Range IOL power (D) Median Range IOP (mm Hg) Median Range Laser flare (ph/msec) Median Range Pupil diameter (mm) Horizontal Median Range Vertical Median Range ECC (cells/mm2) Median Range

Biaxial

Coaxial

22 (63) 13 (37)

27 (66) 14 (34)

P Value .814

.569 74 69 to 78

75 68 to 79

20/80 20/200 to 20/50

20/80 20/200 to 20/40

0.88 3.75 to 0.88

0.63 4.31 to 0.38

.271

Group Exam LOCS II LOCS III LOCS IV Lens opacity meter Median Range

Biaxial

Coaxial

P Value

9 24 2

16 23 2

.468 .468 .468 .905

39 30–49

40 29–50

LOCS Z Lens Opacities Classification System

.535

.571 20/33 0 to 20/20

20/33 0 to 20/20

23.0 19.5 to 32.0

23.0 20.0 to 31.0

22.0 32.0 to 2.0

23.0 31.0 to 0.0

15 11 to 17

14 11 to 18

.511

.650

.790

.311 9 7 to 17

8 7 to 14

6 5 to 7

6 5 to 8

6 5 to 7

6 5 to 8

2787 2578 to 3060

2854 2585 to 3122

.979

.811

they had no pain during surgery and 7 (17%) said they felt slight discomfort; no patient said the surgery was very painful. The difference between groups was not statistically significant (P Z .638). Intraoperative and Postoperative Complications The overall complication rate was 23% in the biaxial group and 24% in the coaxial group; the difference was not statistically significant (P Z 1.000). There were no statistically significant differences in intraoperative or postoperative complications between the 2 groups. Intraoperative In the biaxial group, iris defects occurred in 4 eyes, zonular tears in 2 eyes, and small cracks in the peripheral IOL optic in 2 eyes. In the coaxial group, iris defects occurred in 4 eyes, zonular tears in 2 eyes, and posterior capsule rupture with vitreous prolapse in 1 eye. In these cases, anterior vitrectomy was necessary. Intraoperatively, endothelial opacification was seen in 1 eye and a small crack in the peripheral optic during IOL implantation occurred in another eye.

.708

CDVA Z corrected distance visual acuity; ECC Z endothelial cell count; IOL Z intraocular lens; IOP Z intraocular pressure

difficult to very difficult in 24 cases (68%). The surgeon rated the coaxial procedure as very easy to easy in 5 cases (12%), medium in 14 cases (34%), and difficult to very difficult in 22 cases (54%). The difference between techniques was not statistically significant (P Z .505). In the biaxial group, 24 patients (69%) said they had no pain during surgery and 8 (23%) said they felt slight discomfort; 1 patient (3%) said the surgery was very painful. In the coaxial group, 31 patients (76%) said

Postoperative In the biaxial group at 1 day, corneal epithelial edema at the incision site was seen in 14 eyes (40%), fibrinous reaction in the anterior chamber in 1 eye (3%), and pupil distortion in 1 eye (3%). At 3 days, the corneal edema was unresolved in 10 eyes (30%), 2 eyes (6%) had fibrin in the anterior chamber, and 1 eye (4%) had pupil distortion. At 1 week, the corneal edema was unresolved in 3 eyes (8%), 2 eyes (6%) had fibrin, and 1 eye (3%) had pupil distortion. In the coaxial group at 1 day, corneal epithelial edema at the incision site was seen in 14 eyes (35%), pupil distortion in 3 eyes (7%), and fibrinous reaction in the anterior chamber in 1 eye (3%). At 3 days, the corneal edema was unresolved in 8 eyes (20%), 3 eyes (7%) had pupil distortion, and 1 eye (3%) had fibrin in the anterior chamber. At 1 week, the corneal

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Table 4. Corrected distance visual acuity over time. Corrected Distance Visual Acuity Exam Preoperative Median Range Postoperative 1 day Median Range 3 days Median Range 1 week Median Range 8 weeks Median Range

Biaxial Group

Coaxial Group

20/80 20/200–20/50

20/80 20/200–20/40

20/60 20/100–20/40

20/60 20/100–20/40

20/50 25/100–20/25

20/40 25/100–20/30

20/40 20/60–20/25

20/30 20/60–20/25

20/30 20/50–20/20

20/30 20/50–20/20

P Value .271

.864

.688

.809

Figure 2. Distribution of median EPT (EPT Z effective phacoemulsification time).

.908

edema was unresolved in 4 eyes (10%) and 3 eyes (7%) had pupil distortion; no eye had fibrin. Other The rate of other intraoperative and postoperative complications (eg, iris defects, zonular tears, cracks in peripheral IOL optic, posterior capsule rupture, endothelial opacification) did not differ between groups, occurring in approximately 3% in both groups. No other complications (eg, vitreous prolapse, hyphema, IOL dislocation) occurred in either group. Visual Acuity Table 4 shows the median and the range of CDVA over time. There were no statistically significant differences between the biaxial group and the coaxial group at any postoperative visit. There was no correlation between intraoperative complications and postoperative CDVA. Laser Flare Photometry Preoperatively, there was no statistically significantly difference in laser flare values between the biaxial group and the coaxial group (P Z .311) (Table 2). Postoperatively, median laser flare values were higher in both groups. The median value in the biaxial group was 15 photon counts per millisecond (ph/ms) (range 11 to 20 ph/ms) at 1 day and 19 ph/ms (range 11 to 26 ph/ms) at 3 days, decreasing to 12 ph/ms (range 9 to 24 ph/ms) at 1 week and 11 ph/ms (range 8 to 15 ph/ ms) at 8 weeks. In the coaxial group, the median laser flare value was 11 ph/ms (range 8 to 22 ph/ms) at 1 day and 15 ph/ms (range 10 to 18 ph/ms) at 3 days,

decreasing to 11 ph/ms (range 8 to 20 ph/ms) at 1 week and 11 ph/ms (8 to 14 ph/ms) at 8 weeks. There were no statistically significant differences between the 2 groups. Effective Phaco Time and Phaco Power The EPT was statistically significantly shorter in the biaxial group than in the coaxial group (P!.001, Wilcoxon). The median EPT was 1.34 seconds (range 0.65 to 2.31 seconds) and 5.4 seconds (range 2.19 to 8.45 seconds), respectively (Figure 2). The mean phaco power was statistically significantly lower in the biaxial group than in the coaxial group (P!.001, Wilcoxon). The median power was 3.3% (range 3.0% to 4.6%) and 12.9% (range 9.2% to 16.7%), respectively (Figure 3). Endothelial Cell Count Preoperatively, there was no statistically significant difference in the median ECC between the biaxial group and the coaxial group (P Z .708) (Table 2). Postoperatively, there was a statistically significant decrease in the median ECC in both groups. At 8 weeks, the median ECC was 2444 cells/mm2 (range 2044 to 2902 cells/mm2) in the biaxial group (P Z .008) and 2632 cells/mm2 (range 2378 to 2969 cells/ mm2) in the coaxial group (P Z .074). There was no statistically significant difference between the groups in interindividual ECC loss (P Z .105, Wilcoxon). DISCUSSION In this study, biaxial microincision phacoemulsification was compared with conventional coaxial smallincision phacoemulsification in eyes with increased risk for intraoperative or postoperative complications.

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Figure 3. Distribution of median phaco power.

The most frequent risk factors were pseudoexfoliation, small pupil, zonulysis, and previous vitrectomy or other intraocular surgery. Patient-reported discomfort during surgery was not statistically significantly different between the 2 groups. The EPT was significantly shorter and the mean phaco power significantly lower with the biaxial technique than with the coaxial technique. There were no statistically significant differences in visual acuity between the 2 techniques. Because of underlying pathology, the postoperative visual acuity was expected to be lower than after cataract extraction in eyes without coexisting pathology; therefore, retinal visual acuity was measured preoperatively. No statistically significant differences were found between the 2 techniques in the laser flare values, IOP, or the endothelial cell loss. No statistically significant differences in intraoperative or postoperative complications were found between the biaxial group and coaxial group in our study. The main complications were early postoperative corneal edema surrounding the incision, fibrin reaction in the anterior chamber, and pupil distortion. The pupil distortion may have occurred when a preoperatively small pupil was dilated intraoperatively by stretching or synechialysis. Transient corneal edema, wound leakage, elevated IOP, and fibrin reaction are common complications after cataract surgery.5–11 In our study, there were no cases of wound leakage or elevated IOP. Olson12 evaluated 18 patients with dense cataract of (Rgrade 4 on the LOCS opalescence scale) who had biaxial microincision. He used a 21-gauge ultrasound aspiration needle and a 21-gauge horizontal irrigating

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chopper with a duty cycle of 33%. On the first postoperative day, 7 patients had a CDVA of 20/40 or better; all patients had a CDVA of 20/25 or better after 3 months. The mean EPT was 1.4 seconds (range 0.3 to 5.6 seconds) and the mean phaco power, 2.4% (range 1.5% to 4.8%). These EPT results are comparable to ours. Although the postoperative CDVA was better in Olson’s study, the treatment groups were very different from those in our study. Dada et al.13 performed biaxial microincision cataract surgery combined with silicone oil removal in a vitrectomized eye. They concluded that the technique can be a safe alternative to standard phacoemulsification and can be used for cataract extraction in vitrectomized eyes. Our study included 8 eyes with previous vitrectomy; none of these eyes had intraoperative or postoperative complications. In a previous study,14 we compared biaxial microphacoemulsification with conventional coaxial phacoemulsification in eyes with no coexisting pathology. The median EPT was lower in the biaxial group (1.34 seconds; range 0.65 to 2.31 seconds) than in the coaxial group (5.4 seconds; range 2.9 to 8.45 seconds). Patients in the biaxial group had faster recovery of visual acuity. In the present study, although the EPT was lower in the biaxial group than in the coaxial group, there were no statistically significant differences in visual acuity. However, comparison of the visual acuity results between the 2 studies is not possible given the heterogeneity of the diagnoses in the current study of complicated eyes. Alı´o et al.15 also compared conventional coaxial phacoemulsification and biaxial phacoemulsification in healthy eyes. They found significantly lower mean phaco times, mean total phaco percentages, mean EPTs, and surgically induced astigmatism in the biaxial group than in the coaxial group. These findings agree with the lower EPT and phaco power in the biaxial group in our study of complicated eyes. With any procedure, the surgeon must learn how to avoid and manage complications. One intraoperative complication of biaxial phacoemulsification is phaco tip occlusion, particularly when a highly viscous OVD is used. In addition, highly viscous OVDs are hard to remove completely and OVD remaining in the eye can increase IOP or occlude the anterior chamber. Another risk of the biaxial technique is thermal burn caused by the high temperatures obtained, although this did not occur in our study. Incision size is another factor in the outcomes of phacoemulsification. If an incision is too small, manipulations will stretch it, causing folds in the cornea and impairing the surgeon’s ability to visualize deeper structures. On the other hand, an incision that is too large can cause turbulence in the anterior chamber, possibly

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leading to anterior chamber instability. Surgeons performing biaxial phacoemulsification must take into consideration that the small irrigating probe can limit the rate at which irrigation can be provided to the eye. As a result, when high vacuum is used or after occlusion of the phaco tip, irrigation may not be sufficient to maintain a stable anterior chamber.16,17 Therefore, the biaxial technique has a longer learning curve than the coaxial technique. Recent studies comparing biaxial phacoemulsification and microcoaxial phacoemulsification18–22 describe both techniques as safe and effective with comparable advantages and disadvantages. It seems that at present, most surgeons prefer microcoaxial phacoemulsification over biaxial phacoemulsification based on their level of experience with the coaxial technique. In conclusion, the median EPT was shorter and the median phaco power lower during biaxial phacoemulsification than during coaxial phacoemulsification in complicated eyes. One explanation could be that a sleeve is not used in the biaxial technique, which allows better grooving of the phacoemulsification handpiece into the nucleus. Neither surgical technique was better at reducing intraoperative or postoperative complications in complicated cases.

8. 9. 10.

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First author: Sabine Kurz, MD Department of Ophthalmology, Johannes Gutenberg-University, Mainz, Germany