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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 114  |  Issue : 1  |  Page : 1-12

Comparative study of conventional versus torsional phacoemulsification in management of hard nucleus


1 Benha Teaching Hospital, Faculty of Medicine, Ain Shams University, Cairo, Egypt
2 Professor of Ophthalmology, Faculty of Medicine, Ain Shams University, Cairo, Egypt
3 Assistant Professor of Ophthalmology, Ain Shams University, Cairo, Egypt

Date of Submission22-Mar-2020
Date of Acceptance24-Jun-2020
Date of Web Publication31-Mar-2021

Correspondence Address:
MSc, MD, PhD Mervat S Mourad
Professor of Ophthalmology, Faculty of Medicine, Ain Shams University, 27 Zaker Hussien st Nasr City, flat 4, Cairo, 11471
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ejos.ejos_43_20

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  Abstract 

Background Phacoemulsification acoenergy and shortening the phacotime can decrease this risk.
Aim The aim of this work is to compare the safety and the efficiency of phacoemulsification using conventional and torsional ultrasound modalities for hard nucleus cataracts.
Settings and design This was a prospective randomized interventional study.
Patients and methods A total of 30 eyes of 29 patients having hard nuclear cataract (grades IV and V) were divided into two groups. Group A included 15 eyes whose cataract was operated on by conventional phacoemulsification using the Infiniti machine. Group B included 15 eyes whose cataract was operated on by torsional phacoemulsification using the OZil technology of the Infiniti machine. Intraoperative ultrasound time and cumulative dissipated energy were recorded. Postoperative central corneal thickness (CCT) was measured at days 1, 7, and 30, and specular microscopy was done at 1 month.
Statistical analysis The collected data were coded, tabulated, and statistically analyzed.
Results The mean ultrasound time and cumulative dissipated energy and the amount of irrigating fluid were significantly higher in group A. There was a highly significant decrease in endothelial cell count (ECC) in both groups. ECC was significantly lower in the conventional group than in the torsional group at 1 month postoperatively. CCT in both groups was significantly increased at day 1 and then decreased at 1 week and 1 month but was still significantly higher than the preoperative level. CCT became higher in the conventional group than in the torsional group at all follow-up times, but this was significant only at day 1 and week 1 and not significant at 1 month.
Conclusion Both ultrasound modalities can be used in hard nucleus phacoemulsification. However, the torsional ultrasound proved to be safer. The choice between these technologies is of particular importance when operating eyes with low ECC.

Keywords: conventional phacoemulsification, hard cataract, hard nucleus, torsional phacoemulsification


How to cite this article:
Salman SH, Mourad MS, ElGhazawy RM, Rihan RA. Comparative study of conventional versus torsional phacoemulsification in management of hard nucleus. J Egypt Ophthalmol Soc 2021;114:1-12

How to cite this URL:
Salman SH, Mourad MS, ElGhazawy RM, Rihan RA. Comparative study of conventional versus torsional phacoemulsification in management of hard nucleus. J Egypt Ophthalmol Soc [serial online] 2021 [cited 2021 Jul 30];114:1-12. Available from: http://www.jeos.eg.net/text.asp?2021/114/1/1/313078


  Introduction Top


Phacoemulsification is the main procedure of modern cataract surgery. Over the years, cataract surgery has become safer, with ongoing improvements in power modulation, pulse shaping, and fluidics [1]. However, phacoenergy is still the main risk factor for surgical-induced trauma, especially for corneal endothelial cells [2]. The aim of the recent phacoemulsification research is to reduce phacoenergy and shorten the phacotime [3].

In the conventional ultrasound mode, the phacotip moves forward and backward, and this longitudinal movement produces a jackhammer effect causing repulsion as the phacotip pushes the nuclear fragments away when it moves forward [4].

The OZil torsional hand-piece of the Infiniti vision system replaced the axial movement of a traditional phaconeedle with the sideways oscillation of Kelman tip, which eliminates longitudinal repelling forces at the phacotip, dramatically improving followability and reducing the chatter of fragments [5].

Although the frequency of torsional phacoemulsification is lower (32 kHz) than traditional phacoemulsification (40 kHz), the reduction of the repulsive effect and the added cutting in the lateral direction by torsional phacoemulsification make it more efficient. However, there have been debates about the comparative efficacy and safety of torsional mode ultrasound in hard nucleus cataracts, as compared with longitudinal mode [6].

The loss of endothelial cells is greater with hard than soft nuclei. This is because the increased particulate turbulence occurring with hard nuclear fragments causes the most damage to endothelial cells. This and the added stroke length of higher ultrasound power settings increase the chatter and turbulence of nuclear particles within the anterior chamber [5].


  Aim Top


The aim of this work is to compare the safety and the efficiency of phacoemulsification using the conventional and torsional ultrasound modalities for hard nucleus cataracts.


  Patients and methods Top


This prospective study was done at Ain Shams University Hospitals on 30 eyes of 29 patients with senile cataract. The adult patients and the children parents, included in this study were clearly informed about the purpose of the study, the steps of examination and had to sign an informed consent before inclusion. Data collection was following the laws of Egypt and was compliant with the principles of the Declaration of Helsinki.

The patients were divided into two groups:
  1. Group A included 15 eyes whose cataract was operated on by conventional phacoemulsification using the Infiniti machine.
  2. Group B included 15 eyes whose cataract was operated on by torsional phacoemulsification using the OZil technology of the Infiniti machine.


Patient selection

The patient should be suitable for phacosurgery and have a hard cataract.

The following were the inclusion criteria:
  1. Age-related cataract.
  2. Hard nuclear cataract (grades IV and V) according to Lens Opacities Classification System III (LOCS III).
  3. Centrally clear cornea.


The grading of cataracts was determined according to the LOCS III. Cataracts ranging from NO4/NC4 to NO5/NC5 were included.

Patients were excluded if they had the following:
  1. Corneal guttata or central stromal opacities.
  2. Previous intraocular surgery.
  3. Increased intraocular pressure.
  4. Lens subluxation or zonular dehiscence.
  5. Preoperative anterior or posterior uveitis.
  6. Patients who develop intraoperative surgical complications.
  7. Pathological cataract.


This was a single-blinded study, where the preoperative and postoperative evaluations were done by a doctor who did not know to which group the patient belonged.

Preoperative evaluation

This was done for all patients in the two groups and included the following:
  1. Full history taking.
  2. Full ophthalmic examination including the following:
    1. Slit-lamp examination of the anterior segment.
    2. Intraocular pressure measurement using a Goldmann applanation tonometer.
    3. Fundus examination by indirect ophthalmoscopy and slit-lamp biomicroscopy.
  3. Preoperative central corneal thickness (CCT) using ultrasound contact pachymetry.
  4. Preoperative specular microscopy using Tomey EM-3000 specular microscope.


Operative technique

The surgical technique was fixed in the two groups regarding the following:
  1. Corneal wound size: 2.4 mm.
  2. Viscoelastic substance used: hydroxyl-propyl-methyl cellulose 2.4%.
  3. Irrigating solution: lactated ringer.
  4. Nucleus fracturing technique: stop and chop.
  5. Implanted intraocular lens: foldable acrylic hydrophobic.


In the two groups, phacoemulsification was done as follows:
  1. Creating two paracenteses using a 20-G microvitreoretinal knife.
  2. Viscoelastic injection (hydroxyl-propyl-methyl-cellulose 2.4%).
  3. 2.4-mm main corneal incision.
  4. Capsulorhexis was created using a bent 27-G needle.
  5. Hydrodissection and hydrodelineation were performed using a flattened tip cannula, and then free rotation of the nucleus was done.
  6. Phacoemulsification was performed in all with the Infiniti machine using a microtip (20 G) 0.9-mm 45° Kelman miniflared ABS tip.


A stop-and-chop technique was used:
  1. In group A (conventional group):
    1. During sculpting, we used ultrasound pulse mode with maximum power of 60–80%, pulse frequency of 60 pulses per second, vacuum limit of 60 mmHg, and aspiration flow rate of 30 mmHg.
    2. During quadrant removal, we used ultrasound pulse mode with maximum power of 60%, pulse frequency of 60 pulses per second, vacuum limit of 400 mmHg, and aspiration flow rate of 40 mmHg.
  2. In group B:
    1. During sculpting, continuous linear torsional phacoemulsification was used with maximum setting of 100%, vacuum limit of 60 mmHg, and aspiration flow rate of 30 mmHg.
    2. During quadrant removal, continuous linear torsional phacoemulsification was used with maximum setting of 100%, vacuum limit of 400 mmHg, and aspiration flow rate of 40 mmHg.
    3. Then cortical removal was done using bimanual irrigation-aspiration, followed by foldable intraocular lens implantation, then washing the viscoelastic, and closure of the wound by stromal hydration.


Intraoperative evaluation

In both groups, the following data were collected:
  1. Ultrasound time (UST):
    1. Total time in seconds that conventional or torsional ultrasound remained active which represents how many seconds the foot pedal remained in position three.
  2. Cumulative dissipated energy (CDE):
    1. This reflects the effective phacopower with special correcting factor for the torsional motion and the modified frequency, calculated by the machine as follows:


In conventional ultrasound:

In torsional mode:

The CDE and UST are automatically calculated and displayed on the machine monitor. The frequency of the phacotip in torsional mode is 80% of that in standard phaco (32 kHz in torsional versus 40 kHz in conventional phaco), and the stroke distance of the phacotip in torsional mode is half than in standard phaco. This helps justifying the coefficient of 0.4 [2].
  1. The amount of irrigating fluid:
    1. This is automatically calculated by the phacomachine.


Postoperative evaluation

Routine postoperative examination was done on postoperative days 1 and 7, then at 1 month with measurement of the following:
  1. CCT at days 1, 7, and 30.
  2. Specular microscopy at 1 month.


The amount of endothelial cell loss (ECL) was calculated as a percentage from the initial preoperative endothelial cell count (ECC) as follows:



Statistical analysis

The collected data were coded, tabulated, and statistically analyzed using IBM SPSS statistics (Statistical Package for Social Sciences) (V. 22.0) software, version 22.0 (2013; IBM Corp., Chicago, Illinois, USA).

Descriptive statistics were done for quantitative data as minimum and maximum of the range as well as mean±SD for quantitative parametric data, whereas it was done for qualitative data as number and percentage.

Inferential analyses were done for quantitative variables using independent t test in cases of two independent groups with parametric data and paired t test in cases of two dependent groups with parametric data. In qualitative data, inferential analyses for independent variables were done using χ2 test for differences between proportions. However, correlations were done using Pearson correlation for numerical parametric data.

The level of significance was taken at P value less than 0.05 as significant, otherwise as nonsignificant. The P value is a statistical measure for the probability that the results observed in a study could have occurred by chance.


  Results Top


Our study included 30 eyes of 29 patients. Demographic data showed the mean age in group A (the conventional ultrasound group) was 59.8±4.1 years, whereas in group B (the torsional ultrasound group) the mean age was 58.5±3.0 years, with no significant difference (P=0.342) between the two groups.

Regarding the degree of nuclear opalescence, the mean nuclear density in group A was 4.6±0.5, whereas in group B, the mean was 4.5±0.5, with no significant difference (P=0.724) between the two groups. These data are shown later in [Table 1].
Table 1 Comparison between two groups regarding age and nuclear opalescence

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The mean UST in group A was 141.2±24.5 s (range, 92.0–173.0 s), whereas it was 91.5±22.1 s in group B (range, 56.0–135.0 s). Independent t test used to compare both groups showed that this difference is statistically significant (P<0.001), with UST being shorter in group B, as shown in [Table 2].
Table 2 Comparing ultrasound time (s) among the two groups

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[Table 2] and [Figure 1] show that UST was significantly longer in conventional group than in torsional group.
Figure 1 Comparing UST among the two groups. UST, ultrasound time.

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The mean CDE was 33.4±8.5 in group A, whereas it was 23.8±9.2 in group B. The difference between the two groups was statistically significant (P=0.006), being higher in the conventional group ([Table 3]).
Table 3 Comparing cumulative dissipated energy in the two groups

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[Table 3] and [Figure 2] show that CDE was significantly higher in the conventional group than in the torsional group.
Figure 2 Comparing CDE in the two groups. CDE, cumulative dissipated energy.

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The mean amount of irrigating fluid used was 186.6±39.1 ml in group A, whereas it was 153.7±29.8 ml in group B. The difference between the two groups was statistically significant (P=0.015), being higher in the conventional group ([Table 4]).
Table 4 Irrigation fluid (ml) among the studied groups

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[Table 4] and [Figure 3] show that the amount of irrigation fluid used was significantly higher in the conventional group than in the torsional group.
Figure 3 Irrigation fluid among the studied groups.

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Analyzing the preoperative endothelial between the two groups, there was no significant difference between them.

[Figure 4] shows the preoperative specular microscopy of a 69-year-old patient in group A, where the machine analyzed 176 endothelial cells of an average size of 397 μm each. The endothelial cell density is 2521 cell/mm2. The coefficient of variation, which represents the amount of variation in endothelial cell size or polymegathism, is 41. The pleomorphism or the difference in cell shape is measured and represented by the percentage of hexagonal cells (6 A), which is here 49%.
Figure 4 Preoperative specular microscopy of patient in group A.

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[Figure 5] represents the preoperative specular microscopy of a 56-year-old patient in group B, with ECC of 2572 cell/mm2.
Figure 5 Preoperative specular microscopy of patient in group B.

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Noticing the ECC preoperatively and at 1 month postoperatively and analyzing it by paired sample t test, we revealed the following:
  1. In group A, there was a highly significant (P<0.001) decrease in ECC from a mean of 2442.9±238.8 cell/mm2 preoperative to a mean of 1805.7±209.4 cell/mm2 at 1 month, and this is shown in [Table 5] and [Figure 6].
    Table 5 Endothelial cell count (cell/mm2) and endothelial cell loss (%) in the two groups

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    Figure 6 Comparing the two groups regarding endothelial cell count.

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  2. In group B, there was a highly significant (P<0.001) decrease in ECC from a mean of 2448.9±261.1 cell/mm2 preoperatively to a mean of 2102.1±220.4 cell/mm2 at 1 month, and this is shown in [Table 5] and [Figure 6].


Using independent t test, there was no significant difference between preoperative ECC values between the two groups, which became significantly lower (P<0.001) in conventional group than in torsional group at 1 month postoperatively.

Studying the percentage of ECL between both groups, we found that group A showed a loss of 25.6%±9.8 (range, 3.5–45.2%) compared with 14.0±5.4% (range, 6.1–27.4%) in group B at 1 month. The difference between the two groups was statistically significant (P<0.001) ([Table 5] and [Figure 7]).
Figure 7 Endothelial cell loss (%) at 1 month among the two groups.

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[Figure 8] shows the preoperative and postoperative specular microscopy of a 58-year-old patient from group A with cataract grade IV nuclear density. The preoperative ECC was 2699 cell/mm2, which decreased at 1 month postoperative to 2369 cell/mm2, with an ECL of 12.2% at 1 month. In this patient, the CDE was 25.75 and the UST was 105 s, and the amount of irrigating fluid was 155 ml. Pachymetric measurements taken were 530 μm preoperatively, which increased to 590 at day 1, then reached 580 μm at 1 week, and remained 560 μm at 1 month (pachymetry was done by ultrasound contact pachymetry, that is why the measurements are slightly different from the specular readings of corneal thickness).
Figure 8 Preoperative and 1-month postoperative specular microscopy of a 58-year-old patient with grade IV nuclear density from group A.

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[Figure 9] shows the preoperative and 1-month postoperative specular microscopy of a 57-year-old patient with nuclear density grade IV from group B. The preoperative ECC was 2961 cell/mm2 compared with 2668 cell/mm2 at 1 month postoperative, with an ECL of 9.8%. In this patient, the CDE was 19, UST was 80 s, and the amount of irrigating fluid was 130 ml. CCT was measured, being 520 μm preoperatively, which increased to 590 μm at postoperative day 1, 580 μm at 1 week, and decreased to reach 565 μm at 1 month.
Figure 9 Preoperative and 1-month postoperative specular microscopy of a 57-year-old patient with grade IV nuclear density from group B.

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[Figure 10] shows the preoperative and postoperative specular microscopy of a 60-year-old patient with grade V nuclear density from group A. The preoperative ECC was 2483 cell/mm2 which decreased at 1 month postoperatively to 2048 cell/mm2, with an ECL of 17.5% at 1 month. In this patient, the CDE was 30.23, the UST was 125 s, and amount of irrigating fluid was 160 ml. Pachymetric measurements were taken, being 455 μm preoperatively, which increased to 520 μm at day 1, then reached 490 μm at 1 week, and 480 μm at 1 month (pachymetry was done by ultrasound contact pachymetry, which is why the measurements are slightly different from the specular readings of corneal thickness).
Figure 10 Preoperative and 1 month postoperative specular microscopy of a 60-year-old patient with grade V nuclear density from group A.

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[Figure 11] shows the preoperative and 1-month postoperative specular microscopy of a 55-year-old patient with nuclear density grade V from group B. The preoperative ECC was 2963 cell/mm2 compared with 2300 cell/mm2 at 1 month postoperatively, with an ECL of 13.6%. In this patient, the CDE was 29.3, UST was 93 s, and the amount of irrigating fluid was 150 ml. CCT was measured preoperatively at 522 μm, which increased to 570 μm at postoperative day 1, 528 μm at 1 week, and decreased to reach 520 μm at 1 month.
Figure 11 Preoperative and 1-month postoperative specular microscopy of a 55-year-old patient with grade V nuclear density from group B.

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Studying the change in CCT during the follow-up, we found that the mean preoperative CCT was 531.5±40.9 and 515.5±36.7 μm in groups A and B, respectively, with no significant difference between them ([Table 6]).
Table 6 Central corneal thickness between the two groups

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The mean CCT during the postoperative follow-up in group A was 660.5±93.8, 583.1±40.2, and 547.5±30.1 μm at 1 day, 1 week, and 1 month, respectively, and in group B, it was 587.8±40.0, 549.1±40.3, and 527.7±27.4 μm at 1 day, 1 week, and 1 month, respectively.

Comparing preoperative and postoperative CCT in each group, we found a significant increase in CCT postoperatively compared with preoperative values. CCT in both groups significantly increased at day 1 and then decreased at 1 week and 1 month but was still significantly higher than the preoperative level ([Table 6] and [Figure 12]).
Figure 12 Comparing two groups regarding progression of CCT in um. CCT, central corneal thickness.

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Comparing the two groups using independent t test, there was no significant difference between the two groups regarding CCT before operation; the CCT became higher in conventional group than in torsional group at all follow-up times, but this was significant only at day 1 and week 1 and not significant at 1 month.

Calculating the amount of increase in CCT, at day 1, group A showed a mean increase of 129.1±79.0 μm (24.3±14.6%) in contrast to 72.3±36.7 μm (14.3±7.4%) in group B. At 1 week, it was 51.6±31.1 μm (9.9±6.4%) in group A versus 33.6±30.7 μm (6.7±5.9%) in group B. At 1 month, CCT showed a residual increase of 16.0±28.8 μm (3.3±5.4%) and 12.2±16.5 μm (2.5±3.5%) in groups A and B, respectively. The conventional group showed higher CCT changes than in torsional group at all follow-up times, but this was significant only at 1 day and 1 week but not statistically significant at 1 month ([Table 6] and [Figure 13]).
Figure 13 CCT change (%) from preoperative among the two groups (conventional group in blue and torsional group in yellow). CCT, central corneal thickness.

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  Discussion Top


In this prospective randomized interventional study, we studied two mechanisms of ultrasound phacoenergy in the Infiniti machine. One is the conventional ultrasound modality in which the phacotip moves forward and backward, whereas the other is the torsional ultrasound (OZil) where rotatory movement of the tip occurs, which when combined with a bent Kelman tip produces an arc like movement at the tip end.

The reduction of the repulsive effect and the added cutting in the lateral direction by torsional phacoemulsification make it more efficient. However, there have been debates about the comparative efficacy and safety of torsional mode ultrasound in hard nucleus cataracts, as compared with the longitudinal mode [6].

Results are mainly owing to intraoperative factors. We compared the demographic criteria of our patients, and we found no statistically significant difference in age between both groups, with a mean age of 59.8±4.1 years in group A compared with 58.5±3.0 years in group B. This was important because the degree of lens hardness is influenced by the patients’ age.

We compared the degree of nuclear opalescence, which was 4.6±0.5 in group A, whereas in group B, the mean was 4.5±0.5, with no significant difference between the two groups.

Moreover, comparing the preoperative ECC and CCT, we found no statistically significant difference between both groups, with a mean ECC of 2442.9±238.8 cells/mm2 in group A and a mean of 2448.9±261.1 cells/mm2 in group B, and a mean CCT of 531.5±40.9 μm in group A and a mean of 515.5±36.7 μm in group B.

We also fixed most of the operative factors that could affect the ECC, so the two groups had the following same features:
  1. Corneal wound size: 2.4 mm.
  2. Viscoelastic substance used was hydroxyl-propyl-methyl cellulose.
  3. Irrigating solution: lactated Ringer’s solution.
  4. Nucleus fracturing technique: stop and chop.
  5. Implanted intraocular lens: foldable acrylic hydrophobic.


Studying the UST in the two groups, we found that group A (conventional) needed longer time to emulsify the nucleus than group B (torsional). Mean UST for conventional was 141.2±24.5 s, whereas for torsional, it was 91.5±22.1 s, which means statistically significant lower UST in the torsional group. This was different from what Gonen and colleagues proved in 2012 in their study. In their study, they operated 70 eyes and compared UST between biaxial micro-incision conventional and biaxial micro-incision torsional ultrasound and stated that there was an insignificant difference between both groups. However, in their study, they reported much longer UST in torsional than conventional group (67.8±39 and 80.4±57.8 s for conventional and torsional groups, respectively). Although they included the same nuclear density cataracts and they used machine settings that were very much similar to ours, but in the conventional group, they used microburst ultrasound with an average power of 40% and they used quick chop and bimanual micro-incision techniques in both groups [7].

Supporting our study, Kim et al. [6] included 102 eyes in their study and used the same machine settings as ours and proved that UST was significantly shorter in the torsional group for nuclear opalescence grades II, III, and IV, according to locus III, but was insignificantly shorter in the torsional group for grade V nuclear opalescence. The mean UST for grades II, III, and IV was 61.3±10 and 39.1±9.1 for conventional and torsional groups, respectively, and for grade V was 189.0±13.0 and 148.3±40.1 for the conventional and torsional groups, respectively.

Moreover, Zeng et al. [2] performed their study on 198 patients comparing the UST in hard density cataracts and found significantly lower UST in the torsional group than conventional group, with a P value less than 0.001.

More CDE was used than in group B. Mean CDE in group A was 33.4±8.5, whereas in torsional group it was 23.8±9.2. This might be rendered to the fact that the OZiL torsional oscillation effect reduces the amount of phacoemulsification energy and increases the efficiency required to emulsify nucleus, because it does not produce repulsion and breaks up the cataract by shearing and not by the conventional jackhammer effect. Our numbers are close to what Kim et al. [6] found in 2010 comparing conventional and torsional ultrasound on nuclear grade V (LOCS III). They reported a mean CDE of 30.2±5.1 in the conventional group and 27.9±9.0 in the torsional group, with a P value of 0.324.

However, Liu et al. [8] performed their study on 525 eyes and reported that their mean CDE was 16.51±9.6 in conventional ultrasound and 14.08±8.3 in torsional ultrasound. They included nuclear IV density cataracts. They used similar machine settings compared with our study, but they used quick chop technique, which reflects their lower CDE values.

Moreover, Gonen et al. [7] reported a lower CDE in the torsional group with a mean of 16.9±10.5 in the conventional and 14.2±9.8 in the torsional groups, respectively, using the quick chop technique. Rekas et al. [9] in 2009 included 400 patients in their study with moderate and hard density cataracts and compared longitudinal and torsional ultrasound of the Infiniti machine. They reported slightly lower CDE in the torsional group, which was statistically insignificant.

Regarding the amount of irrigating fluid used, we found in group A statistically significant more fluid was used than in group B. Mean amount used in group A was 186.6±39.1 ml, whereas for torsional, it was 153.7±29.8 ml. This might be rendered to the longer UST used in group A. Our numbers were comparable to Kim et al. [6] comparing conventional and torsional ultrasound on nuclear grades II, III, and IV (LOCS III). They used a mean of 251.3±31.6 ml in the conventional group and 140.4±17.0 in the torsional group, with a P value of 0.01. However, in the same study, they compared also the amount of irrigating fluid on grade V and found no statistically significant difference between the two groups, with a P value of 0.152, and the mean amount was 287.5±12.5 and 295.0±67.2 ml in the conventional and torsional groups, respectively.

In addition, Gonen et al. [7] reported lower amount of irrigating fluid in the torsional group, with a mean of 149.3±69.7 and 123.7±64.3 in the conventional and torsional groups, respectively, but this difference was statistically insignificant, with a P value of 0.116.

In our study, the ECL 1 month after surgery ranged from 3.5 to 45.2%, with a mean of 25.6±9.8% in group A (conventional ultrasound), and ranged from 6.1 to 27.4%, with a mean of 14.0±5.4%, in group B (torsional ultrasound). This shows statistically significant lower ECL in the torsional group at 1 month. Our percentages of ECL were less than the values reported from Gonen et al. [7], who included the same nuclear density as in our study (grades IV and V by LOCS III), which were slightly lower in the conventional group but with no statistically significant difference between the two groups. The mean ECL was 36.5±21.1% in the conventional group and 39.1±22.0% in the torsional group.

Our percentages were higher than those reported in other studies such as Liu et al. [8], where the ECL was 19% in the conventional group and 12.5% in the torsional group, probably because they used less CDE owing to their quick chop technique, and also Zeng et al. [2], which demonstrated ECL of 13.6 and 10.5% in the conventional and torsional groups respectively, but they did not mention their nuclear fracturing technique.

Kim et al. [6] proved that ECL at 1 month was insignificantly less in the torsional group for nuclear opalescence grades II, III, and IV according to locus III, but was insignificantly less in the conventional group for grade V nuclear opalescence. The mean ECL for grades II, III, and IV was 7.92±7.24 for conventional and 3.19±3.62 for torsional group and for grade V was 13.45±16.22 and 23.52±22.16 for the conventional and torsional groups, respectively.

The risk factors for ECL includes older age, small pupil, high nuclear grade, large nucleus, type of IOL implanted, contact of nuclear material to the endothelium, surgical technique, incision size, and viscoelastic type (9, 15, 46, and 47), and so the wide range of ECL between different studies is explained by these multifactors.

Analyzing the CCT during the follow-up, the mean difference in CCT at day 1 postoperatively compared with preoperatively was 129.1±79.0 μm (24.3%) for conventional and 72.3±36.7 μm (14.3%) for torsional ultrasound, with significant difference between both groups, and then at day 7, this difference decreased to 51.6±31.1 μm (9.9%) in conventional and 33.6±30.7 μm (6.7%) in torsional, with significant difference between both groups. However, at 1 month, CCT showed a residual increase of 16.0±28.8 μm (3.3%) and 12.2±16.5 μm (2.5%) in conventional and torsional groups, respectively, with no statistical difference.

Our results were similar to the study by Christakis et al. [13] which reported lower increase in CCT in the torsional group than the conventional group at day 1, and the difference between both groups was significant. Liu et al. [8] and Kim et al. [6] reported similar results to our study, with significant difference between both groups in day 1 and day 7, being lower in the torsional group; this difference became nonsignificant at 1 month but was still lower in the torsional group. The CCT change (μm) at 1 month was −2±12 μm for conventional and −4±13 μm for torsional in the study by Liu et al. [8], whereas in the study by Kim et al. [6], CCT change (%) at 1 month was 4.18±2.84% for the conventional and 3.92±3.09% for the torsional groups for nuclear grades II, III, and IV LOCS III and was 1.78±1.37% for conventional and 4.98±4.69% for the torsional group in grade V LOCS III.

In our study, we tried to find the difference between conventional and torsional ultrasound modalities and their effect on ECL and postoperative CCT in eyes with hard nuclei.

In this study, we reported significantly lower ECL in the torsional group. Moreover, the difference was significantly lower in the torsional group regarding postoperative CCT at day 1 and day 7 only but was not significant at 1 month. Regarding intraoperative parameters such as CDE, UST, and amount of irrigating fluid, they were significantly lower in the torsional group. This proves that torsional ultrasound is more safe and effective for performing cataract surgery for dense nuclei.

Together with active fluidics and intrepid balanced tip, torsional mode appeared to be a more efficient mode with a significant reduction of mean UST and CDE across all NO grades, as compared with the longitudinal mode. Torsional mode was also found to reduce ECL, CCT-change, and BCVA-change as compared with longitudinal mode, but the difference was not found to be statistically significant [10].

Many studies were done to study the effect of torsional ultrasound on corneal endothelium compared with longitudinal ultrasound. Some of these studies figured out that torsional ultrasound causes less ECL than longitudinal ultrasound. This was thought to be owing to the increased effectiveness and the decreased UST and CDE when the tip moves side to side [2],[8],[11]. Some other studies found no significant difference between torsional and longitudinal ultrasound regarding the amount of ECL [6],[7],[12]. This difference in results between studies can be rendered to the fact that endothelial loss is multifactorial and could be attributed to many intraoperative operative factors.

Although both torsional and longitudinal ultrasound are still safe methods of removing uncomplicated senile cataract in a patient with healthy corneal endothelium as healthy endothelium is able to maintain pump function and corneal dehydration over a large range of cell counts, these results are particularly important to consider when planning surgery in eyes with low ECC [12].


  Conclusion Top


Both ultrasound modalities can be used in hard nucleus phacoemulsification as there was no significant difference between them regarding the amount of increased CCT at 1 month. However, the torsional ultrasound proved to be safer as it was associated with lower ECL and less increase in CCT in first day and first week postoperatively and more effective as it was associated with lower UST and CDE. The choice between these technologies is of particular importance when operating eyes with low ECC.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Roger FS. Next generation transversal phaco. A Supplement to EyeWorld 2008; 7:666–667.  Back to cited text no. 1
    
2.
Zeng M, Liu X, Liu Y, Xia Y, Luo L, Yuan Z, Zeng Y. Torsional ultrasound modality for hard nucleus phacoemulsification. Br J Ophthalmol 2008; 92:1092–1096.  Back to cited text no. 2
    
3.
Domingues FG, Moraes HVJr, Yamane R. Comparative study of the density of corneal endothelial cells after phacoemulsification by the ‘divide and conquer’ and ‘quick chop’ techniques. Arq Bras Oftalmol 2005; 68:109–115.  Back to cited text no. 3
    
4.
Davison JA. Cumulative tip travel and implied followability of longitudinal and torsional phacoemulsification. J Cataract Refract Surg 2008; 34:986–990.  Back to cited text no. 4
    
5.
David FC. Improving surgical safety with modern phacotechnology. Cataract Refract Surg Today 2008; 1:120–124.  Back to cited text no. 5
    
6.
Kim DH, Wee WR, Lee JH, Kim MK. The comparison between torsional and conventional mode phacoemulsification in moderate and hard cataracts. Korean J Ophthalmol 2010; 24:336–340.  Back to cited text no. 6
    
7.
Gonen T, Sever O, Horozoglu F, Yasar M, Keskinbora KH. Endothelial cell loss: biaxial small-incision torsional phacoemulsification versus biaxial small-incision longitudinal phacoemulsification. J Cataract Refract Surg 2012; 38:1919–1924.  Back to cited text no. 7
    
8.
Liu Y, Zeng M, Liu X, Luo L, Yuan Z, Xia Y, Zeng Y. Torsional mode versus conventional ultrasound mode phacoemulsification: randomized comparative clinical study. J Cataract Refract Surg 2007; 33:287–292.  Back to cited text no. 8
    
9.
Rekas M, Montes-Mico R, Krix-Jachym K, Klus A, Stankiewicz A, Ferrer-Blasco T. Comparison of torsional and longitudinal modes using phacoemulsification parameters. J Cataract Refract Surg 2009; 35:1719–1724.  Back to cited text no. 9
    
10.
Dasgupta S, Mehra R. Comparative studies between longitudinal and torsional modes in phacoemulsification, using active fluidics technology along with the intrepid balanced tip. Indian J Ophthalmol 2018; 66:1417–1422.  Back to cited text no. 10
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11.
Fishkind W, Bakewell B, Donnenfeld ED, Rose AD, Watkins LA, Olson RJ. Comparative clinical trial of ultrasound phacoemulsification with and without the White Star system. J Cataract Refract Surg 2006; 32:45–49.  Back to cited text no. 11
    
12.
Reuschel A, Bogatsch H, Barth T, Wiedemann R. Comparison of endothelial changes and power settings between torsional and longitudinal phacoemulsification. J Cataract Refract Surg 2010; 36:1855–1861.  Back to cited text no. 12
    
13.
Christakis PG, Rosa MBM. Intraoperative performance and postoperative outcome comparison of longitudinal, torsional and transversal phacoemulsification machines. J Cataract Refract Surg 2012; 38:234–241.  Back to cited text no. 13
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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