Endothelial cell loss: Biaxial small-incision torsional phacoemulsification versus biaxial small-incision longitudinal phacoemulsification

ARTICLE

Endothelial cell loss: Biaxial small-incision torsional phacoemulsification versus biaxial small-incision longitudinal phacoemulsification Tansu Gonen, MD, Ozkan Sever, MD, Fatih Horozoglu, MD, Mustafa Yasar, MD, Kadircan H. Keskinbora, MD, PhD

PURPOSE: To compare clinical results of biaxial small-incision torsional phacoemulsification and biaxial small-incision longitudinal phacoemulsification. SETTING: Department of Ophthalmology, School of Medicine, Namik Kemal University, Tekirdag, Turkey. DESIGN: Randomized controlled clinical trial. METHODS: Eyes with high-density nuclear cataract were assigned to have biaxial longitudinal (microburst mode) or biaxial torsional phacoemulsification. The main outcomes included corrected distance visual acuity (CDVA), central corneal thickness (CCT), central endothelial cell density (ECD), total ultrasound time (UST), cumulative dissipated energy (CDE), percentage total equivalent power in position 3, and balanced salt solution volume. Postoperative follow-up was at 1 day, 1 week, and 1 and 3 months. RESULTS: Each group comprised 35 patients (35 eyes). Three months postoperatively, the mean CDVA for each group was 0.02 logMAR and the mean CCT returned to the preoperative level (PZ.589 and PZ.554, respectively). During the postoperative follow-up, the percentage of mean endothelial cell loss in both groups was between 35.4% and 39.1%; there was no statistically significant difference between the groups (P>.05). The mean CDE, UST, percentage total equivalent power in position 3, and balanced salt solution volume values were similar in the 2 groups (P>.05). CONCLUSION: The risk for high endothelial cell loss should be considered when the phacoemulsification of high-density nuclear cataracts is performed using either method. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2012; 38:1918–1924 Q 2012 ASCRS and ESCRS

The aim of phacoemulsification surgery is to aspirate the crystalline lens using low ultrasonic energy, to protect the surrounding tissues from the thermal and fluidic effects using a smaller corneal incision, and to implant an intraocular lens (IOL) through the same incision. Technical developments now allow phacoemulsification to be performed using a biaxial or microcoaxial approach.1,2 Recent advances in IOL technology and the use of cartridge systems allow IOL implantation in the capsular bag through small corneal incisions. The biaxial phacoemulsification method has several advantages over the coaxial phacoemulsification method. Small corneal incisions may prevent the loss 1918

Q 2012 ASCRS and ESCRS Published by Elsevier Inc.

of the ophthalmic viscosurgical device (OVD) in the eye. This maintains anterior chamber stability and pupil dilation. In addition, the capsulorrhexis can be created and hydrodissection performed more easily, and the risk for posterior capsule rupture may be reduced. The other important advantages of small incisions are less surgically induced astigmatism and faster wound healing.3,4 The sleeveless phaco tip used in the biaxial method obscures the intraocular view less than the coaxial handpiece.5 On the other hand, the separate phaco handpiece captures the lens fragments much easier than the coaxial phaco handpiece. The reason is that with the coaxial phaco handpiece, irrigation from the sleeve tends to push 0886-3350/$ - see front matter http://dx.doi.org/10.1016/j.jcrs.2012.06.051

BIAXIAL PHACOEMULSIFICATION: TORSIONAL VERSUS LONGITUDINAL

fragments away from the phaco tip, making aspiration more difficult.6 In the biaxial method, the irrigation and aspiration (I/A) handpieces are interchangeable; thus, subincisional cortical and nuclear materials can be aspirated easily.3,7 Especially in eyes with highdensity nuclear cataract, the torsional method allows aspiration of the lens with less energy and endothelial cell loss than coaxial torsional phacoemulsification.8 Enhanced torsional phaco software (Ozil IP, Alcon Laboratories, Inc.) prevents phaco-tip occlusion and increases the efficiency of torsional phacoemulsification of hard nuclear cataracts.9 When biaxial phacoemulsification methods do not use a sleeve, it is a significant disadvantage; however, innovations in ultrasonic energy use and phaco-tip technology allow aspiration of the lens with less energy and corneal damage. In this study, we evaluated the intraoperative and postoperative outcomes of biaxial phacoemulsification using the torsional method with enhanced phaco software and the longitudinal method in eyes with high-density nuclear cataract. PATIENTS AND METHODS From June 2011 to August 2011, patients who had senile cataract were included in this prospective randomized observer masked study. The study protocol was approved by the local ethics committee of the University of Namik Kemal and performed according to the Declaration of Helsinki. All patients provided written informed consent. Inclusion criteria were age older than 50 years, age-related grade 4 or 5 nuclear cataract according to the Lens Opacities Classification System III (LOCS III),10 and central corneal endothelial cell density (ECD) higher than 1500 cells/mm2. Exclusion criteria were corneal pathology (eg, stromal or endothelial dystrophy); zonular weakness; pseudoexfoliation; dilated pupil size less than 7.0 mm; high myopia; diabetic retinopathy or senile macular degeneration; and a history of intraocular surgery, glaucoma, or uveitis. The patients were randomly assigned to 1 of 2 equal groups (torsional or longitudinal) using a computer-generated random number table.

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3 times at 5-minute intervals before surgery. Two clear corneal incisions were made at 2 o'clock and 10 o'clock with a 20-gauge MVR knife and 19-gauge MVR knife (BeaverVisitec International), respectively. To minimize fluid leakage, a 2-step corneal tunnel incision method was used. To achieve stability and protect the corneal endothelium, a cohesive OVD (sodium hyaluronate [Microvisc 1.4%]) was injected into the anterior chamber. A 27-gauge cystotome needle (Beaver-Visitec International) was used to initiate the anterior capsulotomy, and a 5.0 to 6.0 mm continuous curvilinear capsulorrhexis was created with a 23-gauge coaxial capsulorrhexis forceps (Geuder GmbH). A 0.9 mm sleeveless phaco tip and 19-gauge irrigating chopper (Geuder GmbH) were inserted through the clear corneal incision at 2 o'clock and 10 o'clock, respectively. After hydrodissection, phacoemulsification was performed using the standard quick-chop technique.11 Residual cortical material was removed using a 20-gauge bimanual I/A system (Alcon Laboratories, Inc.). After OVD was injected into the capsular bag and anterior chamber, a self-closing 2.8 mm wide temporal clear corneal incision was created. A foldable IOL (Acriva UD 613, VSY Biotechnology) was implanted in the capsular bag with a cartridge system. The OVD was removed from the anterior chamber and the capsular bag using the I/A system. For endophthalmitis prophylaxis, 0.1 mL moxifloxacin ophthalmic solution 0.5% (Vigamox) was injected into the anterior chamber after closure of the port incisions by stromal hydration using a balanced salt solution. After surgery, all patients used topical prednisolone acetate 1.0% 6 times a day and moxifloxacin 0.5% 6 times a day. The prednisolone acetate was tapered over 3 weeks. In the torsional group, an Ozil torsional handpiece (Alcon Laboratories, Inc.) and 0.9 mm mini-flared 30-degree Kelman Advanced Bypass System tips were used. The phacoemulsification settings were linear torsional amplitude, 100%; dynamic rise, 0; vacuum, 250 mm Hg; aspiration flow rate, 30 mL/minute; bottle height, 110 cm. The software was enabled with the parameters of longitudinal onset at 95% maximum vacuum, 15 millisecond pulses, and a torsional-to-longitudinal ratio of 1 to 1. In the longitudinal group, phacoemulsification was performed using the same handpiece and phaco tip. The phacoemulsification settings were microburst width, 30 milliseconds; preset power, 40%; dynamic rise, 0; vacuum, 250 mm Hg; aspiration flow rate, 30 mL/minute; bottle height, 110 cm.

Surgical Technique

Ophthalmic Evaluation

All operations were performed using the Infiniti phacoemulsification system with the enhanced phaco software by the same experienced left-handed surgeon (T.G.). Proparacaine hydrochloride 0.5% eyedrops were administered

All measurements were performed by the same masked observer (O.S.). The patients had a complete ophthalmic examination including corrected distance visual acuity (CDVA) (measured on a Snellen chart and converted to logMAR units), slitlamp evaluation, and central corneal thickness (CCT) measurement by ultrasonic pachymetry (Pacscan 300P, Sonomed, Inc.) preoperatively and 1 day and 1 and 3 months postoperatively. The measurement range of CCT for the pachymetry device was between 125 mm and 1000 mm. Central corneal ECD was measured by noncontact specular microscopy (SP-01, Costruzione Strumenti Oftalmici) preoperatively and 1 and 3 months postoperatively. The measurements were performed using a semiautomated method. First, the endothelial cells were counted automatically. Thereafter, marked errors were corrected and counting was performed again. For each measurement, at least 50 adjacent cells were counted. Endothelial

Submitted: February 29, 2012. Final revision submitted: June 21, 2012. Accepted: June 22, 2012. From Namik Kemal University, School of Medicine, Department of Ophthalmology, Tekirdag, Turkey. Corresponding author: Tansu Gonen, MD, Degirmenalti Mah. Gundogan Sitesi B Blok, Daire 6, 59100 Tekirdag, Turkey. E-mail: [email protected].

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cell loss was calculated as follows: endothelial cell loss (%) Z [(preoperative ECD – postoperative ECD)/preoperative ECD]  100. Before the measurements, the pachymetry and specular microscopy devices were calibrated according to the user manuals. At the end of surgery, the total ultrasound time (UST), phaco time, torsional time, cumulative dissipated energy (CDE), percentage total equivalent power in position 3, and balanced salt solution volume (mL) were recorded. The UST is the total time the foot pedal is kept in the third position. The CDE indicates the mean percentage of power spent during the UST. The CDE calculation formula is as follows: CDE Z (torsional time  0.4  average torsional amplitude/100) C (phaco time  average phaco power/ 100) in the torsional group and CDE Z phaco time  average phaco power/100 in the longitudinal group. The percentage total equivalent power in position 3 is the average percentage of equivalent ultrasound power in foot position 3. These values are automatically calculated by the phaco unit's software and are shown on the device's screen.

Table 1. Patient characteristics. Group Parameter Sex, n Male Female Eye, n Right Left Age (y) Mean G SD Range NO, n (%) Grade 4 Grade 5

Torsional

Longitudinal

20 15

18 17

19 16

15 20

69.6 G 7.7 54, 82

72.6 G 8.9 51, 87

25 (57.1) 10 (42.9)

22 (62.9) 13 (37.1)

P Value .546

.339

.134 .358

NO Z nuclear opacity (Lens Opacities Classification System)

Statistical Analysis Based on current data, an ECD of 2500 cells/mm2 with a standard deviation of 300 cells/mm2 was assumed. The expected cell loss after phacoemulsification was 200 cells/mm2 in the torsional group and 400 cells/mm2 in the longitudinal group. With a Z 0.05 and a power of 80% (b Z 0.20), a sample size of 32 eyes per group was calculated. Statistical analysis was performed using SPSS for Windows software (version 16.0, SPSS, Inc.). The differences between groups were assessed using the independent-sample t test and the chi-square test. The relationship between parameters was evaluated using Pearson correlation analysis. A P value less than 0.05 was considered statistically significant.

RESULTS

14 eyes in the torsional group on the first day postoperatively because of severe corneal edema; the difference between groups was not statistically significant (PZ.094). There was no statistically significant difference in the mean CDVA between groups at any time postoperatively (PO.32) (Table 3). The postoperative CDVA was 0.30 logMAR or better in 13 eyes (37%) in the torsional group and 10 eyes (29%) in the longitudinal

Table 2. Intraoperative parameters.

Each group included 35 patients (35 eyes). There was no statistically significant difference in age, sex, operated eye, or nuclear opacification grade between the 2 groups (PO.13) (Table 1). No complications occurred during or after surgery. There were no cases of phaco burn of the corneal incision. In all patients, the corneal incisions at 2 o'clock and 10 o'clock were closed with stromal hydration and the anterior chamber was formed. The mean UST was longer in the torsional group; however, the difference between the 2 groups was not statistically significant (PZ.281). In contrast, the mean CDE and balanced salt solution volume values were lower in the torsional group, although there was no significant difference between the groups (PO.19). The mean percentage total equivalent power in position 3 values were similar in the 2 groups (PO.123) (Table 2). There was no significant between-group difference in the CCT measurements preoperatively or 1 day, 1 week, 1 month, or 3 months postoperatively (PO.53) (Table 3). A CCT measurement could not be obtained in 21 eyes in the longitudinal group and

Group Parameter

Torsional

UST (sec) Mean G SD 80.4 G 57.8 Range 7, 290 Phaco time (sec) Mean G SD 2.5 G 1.5 Range 0.5, 6.9 Torsional time (sec) Mean G SD 77.6 G 57.0 Range 5, 283 CDE Mean G SD 14.2 G 9.8 Range 2.4, 49.3 %TEPiP3 Mean G SD 12.8 G 4.1 Range 5.5, 22.8 Balance salt solution volume (mL) Mean G SD 123.7 G 64.3 Range 39, 261

Longitudinal

P Value

67.8 G 39.0 15, 162

.281

67.8 G 39.0 15, 162

d

d d

d

6.9 G 10.5 2.9, 43.8

.271

11.4 G 3.4 3.6, 22

.123

149.3 G 69.7 60, 343

.116

CDE Z cumulative dissipated energy; %TEPiP3 Z percentage total equivalent power in position 3; UST Z total ultrasound time

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Table 3. Between-group comparison of CDVA, CCT, ECD, and endothelial cell loss over time. Torsional Group Parameter CDVA (logMAR) Preoperative Postoperative 1 day 1 week 1 month 3 months CCT (mm) Preoperative Postoperative 1 day 1 week 1 month 3 months ECD (cells/mm2) Preoperative Postoperative 1 month 3 months ECL (%) Postoperative 1 month 3 months

Longitudinal Group

Mean G SD

Range

Mean G SD

Range

P Value

0.74 G 0.53

0.15, 2.00

0,84 G 0.60

0.15, 2.00

.466

0.77 G 0.66 0.23 G 0.31 0.09 G 0.15 0.02 G 0.05

0.00, 2.00 0.00, 1.30 0.00, 0.70 0.00, 0.15

0.69 G 0.50 0.19 G 0.22 0.06 G 0.09 0.02 G 0.06

0.00, 2.00 0.00, 1.00 0.00, 0.40 0.00, 0.20

.568 .537 .322 .589

554 G 35

502, 657

549 G 37

493, 640

.571

664 G 63 611 G 35 568 G 33 558 G 34

554, 816 534, 705 497, 660 505, 664

650 G 69 606 G 59 566 G 49 552 G 42

540, 798 522, 801 485, 718 490, 670

.532 .657 .787 .554

2543 G 355

1875, 3393

2599 G 338

1862, 3162

.501

1542 G 600 1557 G 533

427, 2627 650, 2612

1654 G 614 1676 G 556

547, 2800 626, 2881

.454 .378

39.1 G 22.0 38.6 G 18.9

5.0, 83.6 5.5, 74.4

36.5 G 21.1 35.4 G 18.8

7.1, 75.7 6.6, 76.9

.626 .490

CCT Z central corneal thickness; CDVA Z corrected distance visual acuity; ECD Z endothelial cell density; ECL Z endothelial cell loss

group at 1 day (PZ.485); in both groups, the CDVA was 0.30 logMAR or better in 27 eyes (77%) at 1 week, 34 eyes (97%) at 1 month, and 35 eyes (100%) at 3 months (PO.650). At 1 month and 3 months, the endothelial cell loss exceeded 35% in both groups. The preoperative and postoperative ECD and endothelial cell loss were not significantly different between the 2 groups (PO.37) (Table 3). Table 4 shows the correlations between the endothelial cell loss after surgery and intraoperative power and fluidics for both methods. DISCUSSION To our knowledge, this is the first randomized controlled clinical study to compare biaxial smallincision torsional phacoemulsification with enhanced phaco software and biaxial small-incision longitudinal phacoemulsification. The purpose was to evaluate phaco machine dynamics and changes in the ECD, CCT, and CDVA after cataract surgery performed with topical anesthesia by the same surgeon using the same surgical technique, OVD, balanced salt solution, and IOLs in patients who had similar nuclear cataract (moderate to hard) and ECD but did not have

cornea pathology, pseudoexfoliation, zonular dialysis, or a history of eye surgery. The CDE, which is the mean percentage of ultrasound power used during UST, has a positive linear correlation with nuclear cataract density.12 In eyes with high-density nuclear cataract, the UST is longer, higher ultrasound power is used, and the balanced salt solution volume increases. Because of advanced phaco-tip designs, the specific chopping technique used, and advances in software (eg, second pulse burst and millisecond-level microburst), the nucleus is efficiently emulsified and aspirated by ultrasound power in eyes with high nuclear cataract density.13 In the longitudinal method, the forward movement and backward movement of the phaco tip tends to push the nucleus at every stroke. Therefore, ultrasound power is interrupted and the efficiency of phacoemulsification decreases. Furthermore, the nuclear fragmentation effect of the phaco tip is higher during forward movement than during backward movement.13 In the torsional method, which came into use in 2006 after software and hardware updates to the Infiniti machine, the phaco tip does not push the nucleus and the conventional jackhammer effect is not observed while rotary oscillation movement is

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Table 4. Correlation between endothelial cell loss and intraoperative parameters in each group. % Endothelial Cell Loss

Parameter

Longitudinal Group

Torsional Group

1 Mo

1 Mo

3 Mo

CDE r value 0.612 0.621 P value !.001 !.001 UST r value 0.610 0.630 P value !.001 !.001 %TEPiP3 r value 0.182 0.141 P value .303 .426 Balanced salt solution volume r value 0.549 0.589 P value .001 !.001

3 Mo

0.264 .137

0.247 .166

0.118 .514

0.139 .442

0.246 .168

0.274 .122

0.458 .007

0.481 .005

CDE Z cumulative dissipated energy; %TEPiP3 Z percentage total equivalent power in position 3; UST Z total ultrasound time

performed with 32 kHz frequency of a curved Kelman tip.13–16 Thus, the phaco tip fragments the nucleus in each direction of its movement (side to side) and enables more efficient use of power. Because a 30degree Kelman mini-flared tip, which is used in the torsional method, is liable to become occluded, especially in eyes with a hard nucleus, it decreases the efficiency of the ultrasound power.17 With the software developed to prevent this, the phaco tip is occluded with nuclear material; when the vacuum percentage (90% to 100%), which is set previously, is attained, serial longitudinal power pulses are produced. In this way, the occluded phaco tip is opened, the time spent on occlusion decreases, the peristaltic pump operates without slowing down, followability increases, the use of balanced salt solution decreases, and unnecessary use of ultrasound power is avoided.9,17 Compared with the coaxial torsional method without the software, the coaxial torsional method with enhanced phaco software provides lower CDE and percentage of total equivalent power in position 3 values in eyes with moderate-density nuclear cataract.17 Hard nuclear cataracts can be aspired with less ultrasound power using the coaxial torsional method than using the coaxial longitudinal method.13 Nonetheless, in soft to hard nuclear cataracts, there is no difference in UST and CDE between the 2 techniques, whereas the percentage total equivalent power in position 3 has been reported to be low with the torsional method.12 It has been reported that in soft nuclear cataracts, lower CDE values are obtained with the biaxial microburst longitudinal method than with

the coaxial microburst longitudinal method, whereas in moderate nuclear cataracts, higher CDE values are obtained with the biaxial torsional method.13,18 In our study of patients with modarate to hard nuclear cataract, the CDE and balanced salt solution volume values were lower and the percentage total equivalent power in position 3 and UST values were higher with biaxial torsional with the enhanced phaco method than with biaxial longitudinal microburst method. However, there was no significant betweengroup difference in these values (PO.05). High vacuum is required to capture and fragment the nucleus in the quick-chop technique. Whereas anterior chamber stability is maintained by a high flow rate and vacuum in the coaxial method, it may not be maintained in the biaxial method. Corneal incisions of the same size with I/A tips were created to prevent this, and fluid leakage was reduced. Bottle height was raised to the maximum level the system allows (110 cm). A 19-gauge irrigating chopper was used for irrigation, and a 20-gauge phaco tip was used for aspiration. The vacuum was set at 250 mm Hg and the flow rate was set at 30 mL/min to allow the surgeon to use the quick-chop technique. Anterior chamber stability was maintained with these parameters during surgery. A disadvantage of small corneal incisions in the biaxial method is that there is no sleeve protection to cool the phaco tip and the phaco tip may cause a corneal burn because of frictional heating.7 If irrigation or aspiration is interrupted or decreases, phaco power can spread to surrounding tissues and cause thermal injury.19 With the help of advanced power techniques, such as the longitudinal microburst method and the torsional method, the risk for corneal burn is reduced.20,21 A way to prevent corneal burn is to create a corneal incision 1-gauge wider than the phaco tip, allowing fluid to flow around the phaco tip and exit, which cools the cornea.6 Although the heat of the incision line steadily rises with continuous longitudinal power, it rises for 5 to 10 sec and then plateaus and remains constant with continuous torsional power.20 In the torsional method, the rotary oscillation movement of the phaco tip allows fluid to flow around the phaco tip and cools the phaco tip and corneal incision. In our study, no burn was observed in any corneal incision and all incisions were closed with stromal hydration. It was thought that high phaco power and fluidic values obtained in both groups were linked to the high-density nuclear cataracts. High ultrasound power, long UST, and high total balanced salt solution volume are the most important intraoperative phaco machine–related factors in excessive endothelial cell loss after phacoemulsification in healthy eyes without a history of intraocular surgery, pseudoexfoliation, or corneal dystrophy.2,22 High-

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density nuclear cataract, increased infusion volume, and a large nucleus are independent predictors of endothelial cell loss in coaxial torsional phacoemulsification.23 Studies8,9,12,24 have shown that the total power applied within the eye is lower with the torsional method than with the longitudinal method and less surgery-related endothelial cell damage occurs. In a study by Wang et al.,18 the endothelial cell loss with the biaxial torsional method was 25% in eyes with grade 4 nuclear cataract (LOCS III grading system) 1 month postoperatively. In another study,2,25 the endothelial cell loss with the biaxial burst-mode longitudinal method was 9.27% in eyes with a nuclear cataract of grade 2 or less (LOCS II grading system) in the first month after surgery. Kurz et al.26 found endothelial cell loss of 14.5% in eyes with nuclear cataract of grade 4 or less (LOCS III) after phacoemulsification with the biaxial pulse-mode longitudinal method. In our study, the endothelial cell loss at 1 month and 3 months was 35% to 40% in both groups. However, the difference between groups was not statistically significant. In the longitudinal group, the endothelial cell loss in the first month and third months showed a significant positive correlation with UST, CDE, and balanced salt solution volume, whereas in the torsional group, the endothelial cell loss in the first month and third month showed a significant positive correlation with balanced salt solution volume. Endothelial cells play a vital role in maintaining corneal transparency.27 There is a close relationship between corneal edema and ECD after phacoemulsification.28 Furthermore, edema formation in the corneal matrix layer due to intraoperative heating can also cause corneal edema.27 A high balanced salt solution volume in the longitudinal method may be a reason for excessive corneal edema.8 On the first day after surgery, the CCT could not be measured in a significant number of patients in the longitudinal group and the torsional group because of excessive edema. Nevertheless, there was not a significant difference in CCT between the 2 groups at any time after surgery. In our study, excessive endothelial cell loss, a high CDE, and a high balanced salt solution volume seemed to cause excessive edema. Three months postoperatively, the mean CCT returned to the preoperative level in both groups. The CDVA in the 2 groups was similar during the postoperative follow-up, and there was no significant difference between the groups. In the longitudinal group and the torsional group, the CDVA was 0.30 logMAR (20/40 Snellen) or better in 29% of patients and 37% of patients, respectively, on the first postoperative day as a result of excessive corneal edema. In a study of eyes with nuclear cataract grade 3 or more (LOCS III) that had surgery with the biaxial

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longitudinal method,29 the uncorrected visual acuity was 20/40 in 39% of patients 1 day postoperatively. In eyes with low-grade cataract that had surgery with the biaxial longitudinal method, the CDVA was reported to be better than 20/40 in 75% to 94% of the patients on the first postoperative day.30,31 The major limitations of our study are that the thickness and morphologic changes of the corneal incisions were not examined and the use of the 2 methods in eyes with soft nuclear cataracts was not be evaluated. The dispersive property of the OVD was not adequate, although it was used in every step of phacoemulsification; this can be regarded as factors in the high rate of endothelial cell loss. It may be more difficult to occlude the nucleus and pull it to the center with a 30-degree mini-flared Kelman tip than with a 45-degree mini-flared Kelman tip.17 We had no difficulty with the 30-degree mini-flared Kelman tip in our study. In conclusion, the effects of biaxial torsional with intelligent phaco and longitudinal methods on CDVA, CCT, and endothelial cell loss were comparable. Whereas balanced salt solution volume was lower in the torsional group, there was no significant difference between the 2 groups in any other perioperative phacoemulsification parameter. The risk for high endothelial cell loss should be considered when phacoemulsification of moderate to hard nuclear cataract is performed using either method. WHAT WAS KNOWN  In eyes with soft to moderate nuclear cataract, the effect of phacoemulsification with both biaxial torsional and biaxial longitudinal techniques on the corneal endothelium is limited. WHAT THIS PAPER ADDS  The biaxial torsional with enhanced phaco software and the biaxial longitudinal phacoemulsification methods may be associated with significant corneal endothelial cell loss in eyes with moderate to hard nuclear cataract.

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J CATARACT REFRACT SURG - VOL 38, NOVEMBER 2012

First author: Tansu Gonen, MD Namik Kemal University, School of Medicine, Department of Ophthalmology, Tekirdag, Turkey