Liquefaction versus Torsional IP: A Comparative

Original Paper Ophthalmic Res DOI: 10.1159/000342974

Received: January 23, 2012 Accepted after revision: July 2, 2012 Published online: $ $ $

Liquefaction versus Torsional IP: A Comparative Study on Endothelial Cells, Corneal Edema and Corneal Sensitivity Georgios Labiris a Zisis Gatzioufas b Athanassios Giarmoukakis a Haris Sideroudi a Vassilios P. Kozobolis a a b

Department of Ophthalmology, University Hospital of Alexandroupolis, Alexandroupolis, Greece; Department of Ophthalmology, University Clinics Saarland UKS, Homburg/Saar, Germany

Key Words Liquefaction ! Torsional IP ! Endothelial cells ! Corneal edema ! Corneal sensitivity

Abstract Background/Aims: To compare the impact of liquefaction and torsional IP cataract extraction methods on endothelial cell count (ECC), central corneal edema, and central corneal sensitivity (CCS) in a sample of cataract patients. Methods: The liquefaction (LG) and torsional IP (TG) group consisted of 47 and 48 grade 2 cataract eyes, respectively. Uncorrected and best spectacle-corrected visual acuity, ECC, central corneal thickness (CCT), and CCS were measured 1 day prior to surgery, 10 days, 1 and 3 months postoperatively. Results: Significant difficulties in the nucleus fragmentation were encountered in 2 LG eyes, and they were excluded from the study. Both techniques provided excellent refractive outcomes (LG, p ! 0.001; TG, p = 0.02). Nonsignificant differences were detected in CCT values at the final postoperative examination; however, TG patients presented higher CCT on the first postoperative day (p = 0.04). Both groups presented comparable significant reductions in ECC (LG, p ! 0.001; TG,

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p ! 0.001) and CCS (LG, p = 0.02; TG, p = 0.02). Conclusion: Both methods provide excellent refractive outcomes, with comparable impact on ECC and CCS. Liquefaction seems to provide less corneal edema; however, difficulties in nucleus fragmentation may be encountered even in grade 2 cataracts. Copyright © 2012 S. Karger AG, Basel

Introduction

Cataract extraction is considered the most prevalent ophthalmological operation both in developing and developed societies. Moreover, phacoemulsification is the primary choice in elective cataract surgery for a vast majority of surgeons [1]. Despite advances in cataract extraction techniques and cataract-related technology, a series of intraoperative and postoperative adverse effects and complications have been associated with this prevalent surgical modality. Among the mild ones are transient corneal edema and reduced corneal sensitivity [2]. More severe ones include permanent corneal decompensation due to endothelial cell damage [2–4]. Georgios Labiris, MD, PhD Department of Ophthalmology University Hospital of Alexandroupolis GR–68100 Alexandroupolis (Greece) E-Mail labiris @ usa.net

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To minimize a phacoemulsification’s impact on endothelial cells and prospectively on the cornea as a whole, a series of improvements have been developed aiming to reduce the amount of energy that is emitted in the anterior chamber [1, 4–7]. Among these improvements is the torsional technology, introduced for the Infiniti Vision System Platform (Alcon, Inc.). The torsional technology uses a customized hand piece that produces rotary oscillations with a frequency of 32 kHz. It actually breaks up the cataract by shearing and not by inducing the conventional jackhammer effect [1]. The torsional IP mode is an upgrade for the torsional phacoemulsification that improves the system’s response upon occlusion of dense nuclear parts. Another alternative to conventional phacoemulsification is liquefaction. The liquefaction technology also uses a customized hand piece which propels warmed micropulses into the lens material. These micropulses are supposed to fragment the nucleus into small pieces which are continuously irrigated. It becomes obvious that the liquefaction mode requires no mechanical motion of the tip [5]. The reduction in corneal sensitivity following cataract extraction surgery has been described by previous investigators [8]. The location and length of the incision and the quality of the preoperative tear film have been associated with the postemulsification sensitivity of the cornea [8, 9]. However, extensive research of the literature provided no data, neither for after torsional nor for after liquefaction cataract extraction. Given this context, the primary objective of this study was the comparative assessment of the impact of the torsional and liquefaction technologies on endothelial cells, corneal edema and corneal sensitivity in a sample of cataract patients. Material and Methods Setting This was a prospective, clinic-based, randomized trial. The study protocol adheres to the tenets of the Helsinki Declaration and written informed consent was obtained from all participants. The Institutional Review Board of the Democritus University of Thrace approved the protocol. The study was conducted at the University Hospital of Alexandroupolis, in Greece, between April and August 2011. Participants The participants were recruited from the Cataract Service of the University Hospital of Alexandroupolis on a consecutive-ifeligible basis. The eligibility criteria included a diagnosis of senile cataract with stage 2 nuclear opalescence according to the Lens Opacities Classification System III (LOCS-3) grading scale [10]. By means of a customized computer randomization program, all

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participants were randomly assigned to 2 study groups according to the cataract extraction technology used: (a) the torsional (TG) and (b) the liquefaction (LG) group. The exclusion criteria for all participants were: an endothelial cell count (ECC) !1,900/mm2, glaucoma, IOP-lowering medications, former incisional surgery, former diagnosis of corneal disease, diabetes or autoimmune diseases. Surgical Technique All operations were performed by the same surgeon (G.L.) in a consistent way using the Alcon Infiniti Vision System platform. The pupils were dilated with tropicamide 0.5% (tropixal, Demo, Greece) and phenylephrine hydrochloride 5% (phenylephrine, Cooper, Greece). The periorbital skin and the lids were cleaned and the conjuctival cul-de-sac was irrigated with povidone iodine (betadine). The patients received topical anesthesia with propacaine hydrochloride 0.5% drops (3 drops prior to surgery). By means of a 2.75-mm, superior-temporal (eleven o’clock), self-sealing, clear-cornea incision, sodium hyaluronate 1.5% and lidocaine hydrochloride 1%, an ophthalmic viscosurgical device (Visthesia, Carl Zeiss, Germany) was injected into the anterior chamber. Capsulorrhexis was done with forceps, and hydrodissection with balanced salt solution. In the TG participants, an 80% continuous amplitude with 350 mm Hg vacuum limit and 40 ml/min aspiration flow rate was applied. On the other hand, in the LG participants, the following parameters were set: 70% linear power, 36 ml/min aspiration flow and 350 mm Hg vacuum limit. In all participants, the foldable hydrophilic acrylic intraocular lens SN60WF (Alcon) was inserted into the capsular bag and the ophthalmic viscosurgical device was thoroughly aspirated. The same postoperative regime was prescribed to all patients which included: a fixed combination of tobramycin 0.3% and dexamethasone 0.1% (tobradex, Alcon, Greece) six times daily, gradually tapered in a month. Data Collection All preoperative and postoperative assessments were done by the same ophthalmologist who was not involved in the study. ECC was measured using a non-contact specular microscope SP-2000P (Topcon, Inc.). Three images were taken with at least 100 endothelial cells in each session and mean values were calculated. Central corneal sensitivity (CCS) was assessed by the Cochet-Bonnet esthesiometer. Central corneal thickness (CCT) measurements were obtained with anterior segment optical coherence tomography (Visante OCT, Carl Zeiss Meditec, Dublin, Calif., USA). Statistical Analysis The normality of the measured data was evaluated by the Kolmogorov-Smirnov test. Normal distribution data were assessed by Student’s t test. Nonparametric data were assessed with the Mann-Whitney U test. Within-group differences on different examination days were evaluated with repeated measures analysis of variance (ANOVA). Bonferroni’s correction was applied as necessary. The measured data were collected 1 day prior to surgery and on the 1st and 10th day, at 1 and 3 months postoperatively. All statistical analyses were performed with Medcalc version 9.6.2.0 (Medcalc Software, Mariakerke, Belgium).

Labiris /Gatzioufas /Giarmoukakis / Sideroudi /Kozobolis

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p = 0.29 p = 0.31

0.8 0.7

0.5

560

CCT (µm)

UVA

0.6

Color version available online

p = 0.24

0.9


1.0

570

p = 0.13

0.4

550 p = 0.04

0.3 0.2

p = 0.08

p = 0.09 LG TG

0.1 0 preoperative BSCVA

1st day

10th day

30th day

p = 0.12

540

p = 0.24

p = 0.45 LG TG

90th day 530 preoperative

Fig. 1. Uncorrected visual acuity (UVA) chart.

Results

1st day

10th day

30th day

90th day

Fig. 2. Central corneal thickness (CCT) chart.

Table 1. Demographics and preoperative data for all study par-

ticipants

95 patients (53 men and 42 women, mean age 73.4 8 11.5 years) were recruited and divided into the TG (47 eyes) and LG (48 eyes) study group. Detailed demographics and preoperative best spectacle-corrected visual acuity (BSCVA) are presented in table 1. Nonsignificant differences were detected for age (p = 0.45, Student’s t test) and BSCVA (p = 0.09, Mann-Whitney U) among the groups. Furthermore, study groups were homogeneous for the preoperative values of ECC (p = 0.324), CCT (p = 0.442) and CCS (p = 0.245, all Mann-Whitney U). Significant difficulties were encountered in 2 LG eyes during liquefaction (inability to fragment the nucleus); therefore, the operation was converted to torsional extraction surgery. Despite uneventful surgical outcomes, these eyes were excluded from the study. TG participants required an average of 4.65 8 1.9 cumulative dissipated energy (CDE), while LG participants required an average of 2,825 8 322 pulses. Following cataract extraction surgery, a significant improvement was detected in the uncorrected visual acuity (UVA) compared to the preoperative BSCVA (LG, p ! 0.01; TG, p = 0.02; ANOVA). On the other hand, nonsignificant UVA differences were detected between the study groups on all postoperative examination days (all p 1 0.05, Mann-Whitney U; fig. 1). Regarding the CCT parameter, nonsignificant differences were detected be-

Study group

Number

Age, years

LOCS

BSCVA

TG LG

37 38

72.8810.9 74.4812.1

stage 2 stage 2

0.2280.17 0.2880.14

p

NA

0.453

NA

0.09

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TG = Torsional group; LG = liquefaction group; LOCS = Lens Opacities Classification System; BSCVA = best spectacle-corrected visual acuity; NA = not applicable.

tween the preoperative and postoperative values for both groups (p 1 0.05, ANOVA). However, TG participants presented higher CCT values on the first postoperative day (p = 0.04, Mann-Whitney U). Nonsignificant differences were detected on the final examination day (p = 0.24, Mann-Whitney U; fig. 2). Regarding the ECC parameter, a significant reduction of endothelial cells was detected in both groups (LG, p ! 0.001; TG, p ! 0.001; ANOVA). A reduction of 7.9 8 3.7% and 9.5 8 4.5% in ECC was detected in the LG and TG eyes on the final examination day, respectively. Nonsignificant differences were detected within the groups for all examination days (fig. 3). On the other hand, nonsignificant differences in the CCS parameter were detected between the LG and TG 3

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2,350 p = 0.16 2,300

p = 0.34

p = 0.31

5.4 5.2 5.0 CCS

ECC (n/mm2)

2,400

5.6


LG TG


2,450

p = 0.23

4.8

p = 0.29

4.6

2,250

4.4 2,200 p = 0.17

p = 0.14

4.2

p = 0.18

p = 0.09

LG TG

p = 0.08

4.0

2,150 preoperative 1st day

10th day

30th day

preoperative

90th day

Fig. 3. Endothelial cell count (ECC) chart.

1st day

10th day

30th day

90th day

Fig. 4. Central corneal sensitivity (CCS) chart.

Table 2. Group comparisons on different examination days Para- Preoperative meter LG TG

1st day p

CCT ECC CCS UVA

0.45 552825 569831 0.16 2,2998465 2,3028470 0.31 4.4481.12 4.2181.21 0.09 0.5980.23 0.5280.29

538829 540829 2,3458443 2,4018435 5.4880.92 5.4580.99 0.2880.14* 0.2280.17*

LG

10th day TG

p

LG

30th day TG

0.04 544827 555832 0.34 2,2018398 2,2558456 0.08 4.6881.01 4.4181.13 0.13 0.8980.18 0.8880.21

p

LG

90th day TG

p

0.08 545828 542834 0.17 2,1658401 2,1998334 0.14 4.8580.94 4.7681.01 0.24 0.9080.16 0.8980.19

LG

TG

p

0.12 542818 543826 0.09 2,1598378 2,1728299 0.23 4.8880.76 4.7980.91 0.29 0.9080.16 0.9080.21

0.24 0.18 0.29 0.31

* Best spectacle-corrected visual acuity.

participants on all examination days. However, neither of the groups regained the preoperative corneal sensitivity (LG, p = 0.02; TG, p = 0.02; ANOVA; fig. 4). All group comparisons are presented in table 2. Potential correlations of the amount of pulses (in the LG group) or CDE (in the TG group) with the ECC, CCT and CCS parameters were nonsignificant (all p 1 0.05). Discussion

The liquefaction technology was developed in an attempt to address known vulnerabilities of other more popular phacoemulsification technologies; among them the negative impact on endothelial cells and on corneal sensitivity and the postoperative corneal edema. Researchers have previously suggested that the Aqualase hand piece induces no incisional thermal damage even at full power [5, 11]. Furthermore, the absence of mechani4

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cal motion of the tip within the eye might suggest less overall impact on the surrounding structures. The torsional technology attempts to address the same vulnerabilities of the conventional longitudinal phacoemulsification. Studies have shown that torsional cataract extraction provides better thermal intraoperative protection [12] and utilizes lower CDE for the same cataract density [1, 13, 14]. Moreover, the new IP software that we used in our study reduces the incidence of clogged tips applying alternating torsional and longitudinal pulses upon occlusion of a dense nuclear part [15]. Therefore, the operation time is reduced primarily due to better followability and better overall behavior of the nuclear parts during emulsification. Concerning our study methodology, we attempted to compare the efficacy of these new technologies in grade 2 cataracts using a homogenous sample of patients. We did not extend our comparisons to harder cataracts, since both literature [2, 5] and personal experience indicate an Labiris /Gatzioufas /Giarmoukakis / Sideroudi /Kozobolis

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average performance of Aqualase in these cases. In fact, 2 LG eyes were eventually operated with torsional ultrasound despite the significant experience of the surgeon in liquefaction. Regarding the refractive outcomes, both technologies demonstrated excellent results with no differences on all examination days. However, a significant reduction in ECC was detected on the final postoperative examination day. In fact, LG eyes have lost 7.9% of their endothelial cells by the final examination day. Ryu and coworkers [11] indicated in their report a total ECC reduction of 4.5%; however, their group consisted of younger patients and their final examination day was 2 months postoperatively. It is well-known that older people present higher endothelial cell losses following cataract extraction [16]. On the other hand, our TG eyes have lost 9.5% of their endothelial cells which is slightly more than in the studies by Reuschel et al. [13] and Storr-Paulsen et al. [17] who reported an average loss of 7.2 and 6.3%, respectively. However, neither study used Visthesia in their patients. In fact, the literature provides conflicting evidence regarding the potential cytotoxic role of lidocaine hydrochloride 1% on endothelial cells. While Poyales-Galan and Pirazzoli [18] in their report suggested no additional cytotoxic effect of Visthesia, Perone et al. [19] indicated a significant impact on ECC when using Visthesia. Moreover, Moschos et al. reported an ECC reduction of 9.6% in their Visthesia group of cataract patients [20]. Nevertheless, regardless of the role of Visthesia, both study groups presented similar endothelial cell loss patterns, suggesting that both technologies have an equal impact on ECC. In accordance with the ECC results, both technologies presented a similar nonsignificant impact on CCT at the final examination time point. However, TG patients presented higher CCT values on the first postoperative day. The aforementioned finding suggests that torsional phacoemulsification might exert a transient negative impact on endothelial cells that becomes nonsignificant during the rest of the postoperative period. However, Nakano and coworkers did not report any association of liquefaction with CCT on any postoperative examination day in their comparative study [21]. Nonsignificant differences between the study groups were detected regarding the corneal sensitivity. Both groups presented a similar reduction in the CCS parameter that did not regain preoperative values on the final examination day of one month. It is known that corneal incision might disrupt the normal pathway of the corneal nerves, especially when located at the temporal side of the eye [8]. Further to the incision, the surgical ma-

nipulation induces an inflammation process, both at the corneal level and in the anterior chamber, which contributes to the reduction of corneal sensitivity [22]. In our case, a clear corneal incision was performed at the eleven o’clock position in order to minimize the impact on the large nerve fibers that run in the nine-to-three o’clock direction [23]. Since no within-group differences were detected, we assume that the impact of cataract extraction technology on CCS is negligible in comparison to the incision itself. However, it should be mentioned that we only evaluated CCS and did not elaborate on potential differences at the incision area for the assessment of a potential thermal effect. Summarizing, to our knowledge this is the first study to compare liquefaction with the new improved torsional IP technology in mild cataracts. Our results suggest that both technologies are equally efficient with excellent refractive outcomes. It seems that liquefaction produces less corneal edema in the immediate postoperative period; however, difficulties in nucleus fragmentation may be encountered even in these cataracts. On the other hand, both techniques induce a comparable impact on endothelial cells and corneal sensitivity. Further studies with larger cohorts of patients are necessary for confirmation of our results and evaluation of these prevalent surgical modalities.

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Acknowledgements We received no financial support for this study. None of the authors has any proprietary interests or conflicts of interest related to the submission of this paper. The manuscript is not simultaneously being considered for publication at any other journal. ClinicalTrials.gov Identifier: NCT01480557.

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