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Journal Français d'Ophtalmologie
Volume 40, n° 9
pages 744-750 (novembre 2017)
Doi : 10.1016/j.jfo.2017.02.013
Received : 1 December 2016 ;  accepted : 8 February 2017
Central corneal thickness assessment after phacoemulsification: Subluxation versus Divide-and-Conquer
Souffrance cornéenne comparée pour deux modes de phacoémulsification : subluxation versus divide-and-conquer

A.-L. Jeancolas a, L. Lhuillier a, L. Renaudin b, M. Boiche a, C. Ghetemme a, C. Goetz b, N. Ouamara b, J.-M. Perone a,
a Department of ophthalmology, Mercy hospital, Metz-Thionville regional hospital center, 1, allée du Château, 57085 Metz cedex 03, France 
b Clinical research support unit, Mercy hospital, Metz-Thionville regional hospital center, 1, allée du Château, 57085 Metz cedex 03, France 

Corresponding author.

To compare the impact of two phacoemulsification techniques (subluxation versus divide-and-conquer) on postoperative corneal edema at postoperative hour 1 and day 4.


Comparative study.


Ninety-six consecutive patients (110 eyes; 43 men and 53 women, mean age 70.9±9.8 years) with equivalent cataract grades underwent cataract surgery and were followed up for 6 months. The presence of corneal edema was determined using central corneal thickness (CCT). CCT was measured preoperatively, and at postoperative hour 1 and day 4.

Main outcome measures

Ultrasound power (US %), duration of ultrasound (TPA), effective ultrasound time (TPE), surgical duration and final suture (%).


Eyes of participants were divided into two phacoemulsification technique groups: subluxation (n =50 eyes) and divide-and-conquer (n =60 eyes). Non-inferiority analysis revealed similar CCT increases at postoperative hour 1 in both groups, with 69.9±44.9μm and 64.4±42.9μm, observed in the subluxation and divide-and-conquer groups, respectively (P =0.033). TPE was similar in both groups, taking 6.2±3.4 and 7.3±4.5seconds in the subluxation and divide-and-conquer groups, respectively (P =0.150). No correlation was seen between TPE and edema at postoperative hour 1, or between TPE and day 4 edema. Rate of final suture use was similar between the subluxation and divide and conquer groups, at 36% and 30%, respectively.


The study findings suggest that cataract surgery performed using the subluxation technique does not result in greater CCT than the divide-and-conquer technique. CCT appears to normalize by postoperative day 4, regardless of the technique used.

The full text of this article is available in PDF format.

Notre étude a pour but d’évaluer la souffrance cornéenne en postopératoire immédiat et à j4 d’une chirurgie de la cataracte par phacoémulsifiaction en fonction de la technique opératoire employée (subluxation versus divide-and-conquer ).

Patients et méthodes

Quatre-vingt-seize patients (110 yeux) consécutifs présentant des cataractes de grades équivalents et opérés par phacoémulsification (microcoaxial 2,2mm) sous anesthésie topique ont été inclus de manière prospective dans notre service entre octobre 2013 et mars 2014. Deux groupes ont été analysés comprenant respectivement 50 yeux pour le groupe 1 (subluxation) et 60 yeux pour le groupe 2 (divide-and-conquer ). Tous les yeux ont été opérés par le même opérateur expérimenté avec phacoémulsificateur Stellaris (Bausch & Lomb, Inc.) et implantation par IOL souples pliables. Les épaisseurs cornéennes centrales (ECC) préopératoires, postopératoires immédiates et à j4 ont été mesurées à partir du tonopachymètre non contact Tonopachy™ NT-530P (Nidek CO, Ltd). Les paramètres relevés étaient : puissance d’ultrasons (US) (%), temps d’utilisation d’ultrasons (TPA), temps efficace d’ultrasons (TPE), durée d’intervention, % de suture finale.


Notre étude a porté sur 110 yeux de 43 hommes (39 %) et 53 femmes (61 %), l’âge moyen était de 70,9±9,8 ans, les temps opératoires moyens étaient similaires dans les deux groupes : 7,7±1,6min (groupe 1) et 7,3±1,5min (groupe 2). Pour l’augmentation d’ECC en postopératoire immédiat, on ne note pas de différence significative entre les deux groupes dans notre analyse de non-infériorité : 69,9±44,9μm (groupe 1) vs 64,4±42,9μm (groupe 2) (p =0,0328). Les temps efficaces d’US étaient similaires dans les deux groupes (6,2±3,4 secondes [groupe 1] vs 7,3±4,5 secondes [groupe 2] [p =0,15]). Le temps efficace d’US n’est pas corrélé à l’importance de l’œdème cornéen postopératoire immédiat et ne conditionne pas la récupération à j4. Le pourcentage de suture finale était comparable : 36 % (groupe 1) contre 30 % (groupe 2).


La technique de subluxation du cristallin lors d’une phacoémulsification est une méthode jusqu’alors peu décrite dans la littérature et qui semble redoutée pour son hypothétique retentissement sur l’endothélium cornéen. Or elle s’avère être une méthode fiable, efficace et rapide, sans majoration de l’œdème cornéen postopératoire par rapport à la méthode classique de divide-and-conquer . On retrouve même dans notre étude un œdème moins important en postopératoire immédiat. Ces données restent à être confrontées aux données de la littérature future, sur des échantillons à grande échelle.


Cette étude montre que la technique de subluxation n’engendre pas d’œdème postopératoire plus important que la technique du divide-and-conquer . À j4 postopératoire, on note un retour à la normale de l’ECC quelle que soit la technique utilisée.

The full text of this article is available in PDF format.

Keywords : Cataract surgery, Phacoemulsification, Cornea, Central corneal thickness

Mots clés : Cristallin, Cataracte, Phacoémulsification, Épaisseur cornéenne centrale, Œdème cornéen


Phacoemulsification is the procedure of choice for most surgeons performing cataract surgery [1]. Alternative techniques have been in development over the last twenty years, with the hope of optimizing operating times, total ultrasound energy used, patient safety, patient satisfaction (especially by maintaining the endothelium to minimize short and long term adverse effects on vision), and visual recovery associated with cataract surgery.

Advancements in surgical techniques and equipment have led to a dramatic increase in the popularity of phacoemulsification, along with increased safety and efficacy [2]. Divide-and-conquer is the parent nucleofracture technique. Since its original description by Gimbel in 1985, its improvement has remained a focus within the field. As such, numerous variations have been developed, allowing it to become the gold standard in cataract surgery [2]. It is a safe technique that is reliable, relatively simple to learn, and serves as a good fallback procedure. The technique was developed to facilitate subdivision of the nucleus into small pieces so that they could be removed more efficiently.

The subluxation technique is a newer technique that is less frequently used because of an increased risk of corneal endothelium damage. As a new technique, the potential advantages and disadvantages of this surgical procedure have not been investigated or described in existing literature. However, in our experience, the subluxation technique seems to be quicker and more efficient than other methods, and provides better management of fortuitous lens subluxation during hydrodissection — a technique involving nuclear extraction by phacoemulsification in two steps after the subluxation.

The aim of this comparative study was to evaluate corneal edema immediately after surgery performed with the subluxation technique versus divide-and-conquer. Corneal edema was determined by measuring central corneal thickness (CCT).

Patients and methods

This prospective study was conducted at Metz-Thionville Regional Hospital, Metz, France. A total of 96 patients were enrolled (110 eyes) and all underwent phacoemulsification cataract surgery over a 6-month period. Approval was obtained from the local ethics committee and all procedures were carried out in accordance with the guidelines of the Declaration of Helsinki. Written informed consent was obtained from all study participants.

Participants were divided into 2 groups: 50 eyes in group 1 where subluxation was performed, and 60 eyes in group 2, in which divide-and-conquer was performed. All the surgeries were carried out using the same phacoemulsification device (Stellaris, Bausch & Lomb. Inc.) and by the same senior surgeon (J.M.P.).

Patients were aged 54 to 87 years old (average±SD=71.0±9.9 years). Inclusion criteria were: the presence of a senile cataract with equivalent grades and history of visual acuity regression. Patients with total white cataract, history of ocular surgery and other eye diseases (corneal pathology, uveitis, glaucoma) or systemic diseases with the potential to affect vision were excluded from the study. Preoperative ocular assessment included: best corrected visual acuity, slit lamp biomicroscopy, fundus examination, biometry, air-puff tonometry and pachymetry using non-contact device Tonopachy™ NT-530P (Nidek CO., Ltd) [3].

Preoperatively, all patients received topical anesthaesia with 0.4% oxybuprocaine hydrochloride (Thea, France). Preoperative mydriasis was induced using an ophthalmic insert containing Tropicamide/Phenylephrine 0.28mg/5.4mg (Thea, France). Cataract removal involved a number of steps in the following order: insertion of a lid speculum to hold the eyelids open, creation of a mini-incision coaxial phacoemulsification (2.2mm) with two side-port stab incision (Beaver Visitec International, MA, USA), and creation of a second incision at 90° to the main incision using a 20-gauge needle. The anterior chamber was then filled with viscous dispersive (DuoVisc, Alcon, Belgium) to maintain a stable anterior chamber depth and protect the corneal endothelial cells from damage during the entire surgical procedure. Finally, a continuous curvilinear capsulorhexis (CCC) was made, followed by hydrodissection.

Figure 1, Figure 2 show the two phacoemulsification techniques used. At the end of the cataract surgery, a flexible intraocular lens was inserted into the capsule bag, the incision was closed with or without suture, and 0.1mL of intracameral cefuroxime (Thea, France) was injected.

Figure 1

Figure 1. 

Subluxation technique. I. During hydrodissection, push water to rotate the nucleus up, to place it into the pupillary area. II. Phacoemulsification of the part going over the pupillary area in the anterior chamber. III. Using the ultrasonic probe rotate the half of 180°. IV Phacoemulsificate the remaining half of nucleus.


Figure 2

Figure 2. 

Divide-and-conquer technique. I. Start a first wide groove. II. Rotate the nucleus. III. Make a second wide groove to create 4 quadrants. IV. Place instruments deep in the groove to crack and separate the 4 nuclear pieces. V. Phacoemulsification of the pieces one by one.


As shown in Figure 1, group 1 eyes were operated on using the following subluxation technique:

nucleus hydrodissection to subluxate it in the pupillary area;
emulsification of the upper part of nucleus;
rotation through 180-degree angle of the remaining half of nucleus;
emulsification of the remaining half of the nucleus.

As shown in Figure 2, group 2 eyes were operated on using the classic divide and conquer technique.

The main outcome parameters assessed in both groups were the mean ultrasound power or phacoemulsification time (% US power), ultrasound time or average phacoemulsification power (UST) and the effective phacoemulsification time (EPT). The UST represented the number of seconds the foot pedal remained in the third position. The EPT was the equivalent phacoemulsification time at 100% power (EPT=phacoemulsification time×average phacoemulsification power). The US power, UST and EPT values were automatically calculated by the device and displayed on the monitor of the machine [4]. Secondary outcomes assessed included surgery duration (min) and suture use.

CCT measurements were taken preoperatively, 1hour after surgery, and at postoperative day 4. Postoperative edema was assessed at 1hour using the formula: CCT1hourCCT preoperative and at day 4, using the formula: CCTday 4CCT preoperative.

Statistical analysis

An unpaired t -test was used to compare quantitative variables, while a χ 2-test was used to compare categorical variables between the two groups. A non-inferiority test using the two one-sided test approach was used to compare postoperative corneal edema. A P -value of less than 0.05 was used to define statistical significance. Statistical analysis was performed using SAS/S\TAT software version 9.3 (SAS Institute Inc.) software.


A total of 110 eyes of 96 patients were enrolled in this study. Of these, 50 eyes underwent surgery via the subluxation technique (group 1) and 60 eyes received the classic divide-and-conquer technique (group 2).

Group 1 included 19 men (38%) and 26 women (62%). Group 2 included 24 men (40%) and 27 women (60%). Mean patient age for group 1 and group 2 was 69.7 and 72 years, respectively, as shown in Table 1.

Patients in group 1 had a significantly shorter mean postoperative time than those in group 2, at 7.3±1.5min versus 8.2±1.6min (P =0.003). However, as shown in Table 2, no statistically significant difference was found between the US, UST and EPT of both groups.

Rates of postoperative suture use to seal the corneal incision were similar in both groups, with 18 eyes in group 1 (36%) needing postoperative suture and 18 eyes in group 2 (30%; P =0.500). However, no significant correlation was observed between suture application and postoperative corneal edema (P =0.330).

A non-inferiority study was conducted to compare postoperative edema rates. A mean 1-hour postoperative edema thickness of 68.8μm, 95% CI (56.0; 81.6) occurred in group 1 versus 64.4μm, 95% CI (53.3; 75.5) in group 2.

Mean postoperative day 4 edema thickness was 11.7μm, IC95% (5.2; 18.0) in group 1 and 9.1μm, IC95% (4.3; 13.9) in group 2.

As demonstrated in Table 3, non-inferiority tests showed that postoperative edema is not greater with subluxation than with divide and conquer at postoperative hour 1 and day 4.

Finally, no intraoperative or postoperative complications occurred in both groups during the study.


Phacoemulsification surgery is known to induce permanent or temporary corneal endothelial damage and is associated with endothelial cell loss [5]. Existing literature have shown a relationship between immediate corneal edema and endothelial cell loss [6, 7], (although it is worth noting that while corneal edema is a recognized complication of the surgery, it is usually short-lived and resolves spontaneously) [8, 9]. As corneal edema is a simple, reproducible and operator-independent outcome, it is an ideal study outcome for assessing postoperative corneal damage and thus comparing the safety and efficacy of different surgical techniques. Endothelial cell loss can be influenced by preoperative and postoperative factors, such as ultrasound power, hand-piece vibrations, nuclear fragments, irrigation solutions, air bubbles or mechanical trauma from surgical instruments [10, 11, 12, 13, 14, 15]. All of these parameters show that endothelial cell loss can vary according to the surgical technique [16, 17, 18].

The subluxation technique is a surgical method that is yet to be explored in detail by published literature. It is similar to the tilt-and-tumble technique described by Lindstrom in 2002, but performed in micro-coaxial mode [19]. It requires an experienced surgeon and appears to be fast and reliable.

The main aim of the current study was to compare postoperative corneal edema following use of two phacoemulsification techniques: subluxation versus divide-and-conquer. Measurements of CCT thickness were made, using the non-contact Scheimpflug camera system, which is a validated method [20, 21, 22, 23, 24, 25]. The Tonopachy™ NT-530P (Nidek CO., Ltd) is a device that has strong evidence for being highly accurate and reliable in existing literature, particularly in comparison with the measurements provided by ultrasonic pachymetry or corneal topography Orbscan [26, 27, 28]. It gives precise pachymetry measurements that are fast, reproducible, reliable, and operator-independent.

We were unable to compare our results to other studies due to the lack of studies conducted using the tilt-and-tumble technique, however, phacoemulsification studies have shown similar postoperative results in terms of corneal edema. The range of postoperative corneal edema reported in our study is comparable to that found in existing literature: at 1hour (76μm), day 1 (35μm), day 7 (3.8μm) [29].

Many studies have suggested that postoperative increase of CCT is an appropriate clinical criterion for assessing endothelial cell loss. Cheng et al. (1988) showed a direct positive linear correlation between the increase of postoperative corneal thickness at day 2 and day 5, and the percentage of endothelial cell loss at 1 and 6 months [5].

A few years later, in 2005, Lundberg et al. confirmed this hypothesis by demonstrating a direct relationship between the increase of CCT at day 1 and central endothelial cell loss at 3 months [7]. In contrast, Ventura et al. 2001 failed to identify a correlation between corneal thickness and endothelial cell density either preoperatively or postoperatively [30].

Based on the results of these studies, conducting a larger scale study comparing corneal edema and endothelial cell loss using specular microscopy measurements would be worthwhile. Furthermore, it has been shown that the duration of phacoemulsification intervention and high ultrasonic powers correlate with an increase in endothelial cell loss [31]. Our study suggests that EPT is related to postoperative corneal edema, but given the small number of participants in the current study, confirmation of this correlation was not possible. In light of this study limitation, we are currently conducting a large scale study (Clinical trial Identifier: NCT02535819) to compare the two phacoemulsification techniques. The primary outcomes will include endothelial cell density and central edema measurements.


In conclusion, the subluxation technique appears to be faster than divide-and-conquer, with comparable postoperative complication rates and immediate postoperative CCT increase.

At postoperative day 4, regardless of the used technique, all patients regained their initial CCT. Given hypotheses made in existing literature, we assume that endothelial cell loss is also not increased by this technique, but acknowledge that a specular microscopy study will be helpful in confirming this theory.

Disclosure of interest

The authors declare that they have no competing interest.


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