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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 17  |  Issue : 3  |  Page : 137-142

Effect of intraocular lens insertion speed on surgical wound structure during phacoemulsification


Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt

Date of Submission25-Mar-2016
Date of Acceptance15-Apr-2016
Date of Web Publication6-Dec-2016

Correspondence Address:
Mohamed B Goweida
Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-9173.195247

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  Abstract 

Purpose
The purpose of this study was to evaluate the difference in the effect of two speeds of intraocular lens (IOL) insertion on the clear corneal wound structure of two sizes: 2.4 and 2.2 mm.
Setting
This study was conducted in the Department of Ophthalmology, Faculty of Medicine, Alexandria University, Egypt.
Design
This is a prospective randomized clinical trial.
Patients and methods
Eyes that had phacoemulsification and Acrysof IQ IOL implantation using a screw-plunger-type injector were randomly divided into two equal-sized groups as follows. Group A included 40 eyes in which an incision of 2.4 mm size was used. These eyes were randomly divided into two equally sized subgroups: group AF with fast IOL insertion [1 revolution per second (rps)] plunger speed, and group AS with slow IOL insertion (1/4 rps). Group B included 40 eyes in which an incision size of 2.2 mm was used. These eyes were randomly divided into two equally sized subgroups: BF with fast IOL insertion (1 rps) and BS with slow IOL insertion (1/4 rps). The change in wound size before IOL insertion and after IOL insertion, need for corneal hydration, and surgically induced astigmatism were compared.
Results
The change in wound size was significantly larger in groups AS and BS than in groups AF and BF (P=0.002 and 0.008, respectively). Corneal hydration was required in 35% of cases in group AF and in 65.0% of cases in group AS. In group B, wound hydration was required in 30.0% of cases in group BF and 60% of cases in group BS. The differences were statistically not significant (P=0.057 and 0.736, respectively).
Conclusion
With an injector system, slow IOL insertion affected clear corneal wound size to a greater extent than fast insertion in the two wound sizes: 2.4 and 2.2 mm.

Keywords: change in wound size, corneal hydration, intraocular lens insertion speed, surgically induced astigmatism


How to cite this article:
El Massry AA, Shama A, Goweida MB, El Zawawi RA. Effect of intraocular lens insertion speed on surgical wound structure during phacoemulsification. Delta J Ophthalmol 2016;17:137-42

How to cite this URL:
El Massry AA, Shama A, Goweida MB, El Zawawi RA. Effect of intraocular lens insertion speed on surgical wound structure during phacoemulsification. Delta J Ophthalmol [serial online] 2016 [cited 2020 Feb 23];17:137-42. Available from: http://www.djo.eg.net/text.asp?2016/17/3/137/195247


  Introduction Top


The evolution of cataract surgical techniques over the past several decades has been associated with a progressive decrease in the size of the cataract incision.

The widespread use of foldable intraocular lenses (IOLs) has allowed the cataract wound to decrease to 3.0 mm or smaller [1].

The smaller the incision, the more stable the anterior chamber, with improved control during capsulorhexis and hydrodissection. It reduces surgically induced astigmatism (SIA), intraoperative and postoperative inflammation, and leads to more rapid visual rehabilitation [2],[3],[4],[5].

At the end of surgery, one of the main concerns is corneal sealing of the incisions. The cornea is less tolerant to stretching and distortion than the sclera. If the cataract incision is inadequate in width and subjected to stretching by surgical instrumentation or during the insertion of the IOL, it is less likely to maintain its integrity. An entry wound that is too narrow and distorted during surgery will be more apt to leak than a modestly larger but less traumatized incision [6].

The same concern arises with regard to the final integrity of the clear corneal incisions: namely, the distortion that may happen during the insertion of the IOL at the end of surgery.

When injector systems are used, the incision size for IOL implantation is determined by the outer diameter of the cartridges and the IOL [7],[8],[9],[10],[11].

Incisions are smaller with injector systems than with IOL implantation using forceps [12],[13].

During the use of the injector to introduce the IOL, we may adopt the direct implantation technique in which we attempt to insert the complete cartridge tip of the injector ∼15% through the limbal incision to allow direct implantation of the leading haptic and IOL optic in the capsular bag. In the ‘wound-assisted’ technique, the cartridge tip is placed bevel down in the incision tunnel, and it does not go through the limbal incision. The patient is asked to look toward the injector system during IOL implantation [14].

A clear corneal wound is considered vulnerable to the stress caused by an IOL injector. Thus, it is reasonable to assume that the time required for an IOL to pass through the wound during insertion may affect wound damage. It could be argued that the slower injection may be less traumatic because it allows the cornea stroma to mold and stretch to accommodate passage of the IOL rather than possibly tearing the incision, which may result from rapid insertion. An alternative hypothesis was that the more rapidly the IOL could be injected through the incision, the less time there would be for the IOL to begin to re-expand (in the incision) toward its natural shape once it leaves the mouth of the cartridge [15].

The purpose of this study was to examine the impact of two speeds of IOL insertion on two surgical wound sizes (WS): 2.4 and 2.2 mm.


  Patients and methods Top


The study included 80 eyes scheduled for phacoemulsification and IOL implantation of a hydrophobic acrylic lens (Acrysof SN60WF) (Alcon laboratories Inc., Fortworth, Texas, USA) using a screw-plunger-type injector Monarch III attached with a D cartridge (both Alcon laboratories Inc.).

The included eyes were divided into two groups.

Group A: included 40 eyes

Surgery was performed through a posterior limbal 2.4-mm clear corneal incision using a steel knife (Slit Knife 2.4 DB; Alcon laboratories Inc.). Eyes were randomly divided into two equally sized subgroups:

  1. Group AF: fast IOL insertion. The screw of the plunger was rotated 1 revolution per second (rps).
  2. Group AS: slow IOL insertion. The plunger speed was 1/4 rps.


Group B: included 40 eyes

Surgery was performed through a posterior limbal 2.2-mm clear corneal incision using a steel knife (Slit Knife 2.2 DB; Alcon laboratories Inc.). Patients were randomly divided into two equally sized subgroups:

  1. Group BF: fast IOL insertion (1 rps).
  2. Group BS: slow IOL insertion (1/4 rps).


Phacoemulsification was performed using the Infinity Vision System (Alcon laboratories Inc.) with an attached 45° Kelman 0.9 mm miniflare ABS phaco tip and Ultrasleeve (Alcon laboratories Inc.).

Exclusion criteria

Exclusion criteria were as follows:

  1. An implanted IOL power less than 17.50 diopter or greater than 28.50 diopter.
  2. Compromised corneas: cicatricial corneal disease, autoimmune diseases, and previous refractive surgery.


Randomization

Each surgery was randomly assigned to group AF, group AS, group BF, or group BS by the envelope method. The envelopes include a memo note denoting the assigned group. The surgeon randomly picked one envelope before every surgery, and opened it to ascertain which incision size and which IOL insertion speed will be used. The envelope was then immediately discarded.

Outcome measures

In all eyes

  1. The WS before and after IOL insertion was measured using a Tsuneoka microincision gauge (American Surgical Instruments Corp., Westmont, Illinois, USA).
  2. Corneal astigmatism was measured preoperatively and 1 week postoperatively to calculate the SIA. Corneal astigmatism was measured using an ARK-560A autorefractor keratometer (Nidek, Gamagori-shi, Japan).


The SIA was measured using doctor-hill website with the following link: http://www.sia-calculator.com.

Statistical analysis

The Mann–Whitney U-test was used to compare patients’ age, IOL power, wound enlargement after IOL insertion, and SIA. Discrete variables between the two groups were compared using the Fisher exact probability test. The results were presented as the mean±SEM unless otherwise noted. Differences with a P less than 0.05 were considered statistically significant.


  Results Top


Eighty patients, 20 in each subgroup, were enrolled in this study. All patients completed the examinations. [Table 1] shows the baseline characteristics in the four subgroups of patients (group AF, group AS, group BF, and group BS) regarding sex and age. There was no statistically significant difference between the four subgroups regarding male and female enrollment. The mean age in the four groups was 69.05±7.65, 68.30±7.97, 66.0±8.80, and 68.60±7.76 years, respectively. There was no statistically significant difference regarding age in the four subgroups. Similarly, there was no statistically significant difference between the four groups as regards right and left eyes ([Table 2]).
Table 1 Comparison between the four studied subgroups according to demographic data

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Table 2 Comparison between the four studied subgroups according to eye

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The mean IOL power implanted in the four subgroups was 21.53±2.36, 21.42±2.37, 21.55±2.57, and 21.73±2.65 diopter, respectively. The least IOL power was +17.5 diopter, and the highest IOL power was +28.0 diopter. There was no statistically significant difference comparing the four subgroups according to the power of the implanted IOL, as shown in [Table 3].
Table 3 Comparison between the four studied subgroups according to IOL power

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[Table 4] compared the clinical data by IOL insertion speed. In group A with original WS of 2.4 mm, the mean WS before IOL insertion was 2.41±0.03 in the fast subgroup and 2.42±0.04 in the slow subgroup, with no significant difference (P=0.955). The mean WS after IOL insertion in group A was 2.43±0.06 in the fast subgroup and 2.46±0.06 in the slow subgroup, with no statistically significant difference (P=0.504).
Table 4 Comparison between the four studied subgroups according to WS

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In subgroup AF, the WS before IOL insertion was 2.41±0.03 mm and after IOL insertion was 2.43±0.06 mm; there was no statistically significant difference (P=0.104).

In subgroup AS, the WS before IOL insertion was 2.42±0.04 mm and after IOL insertion was 2.46±0.06 mm, which is a statistically significant difference (tP=0.002*).

In group B, with original designated WS of 2.2 mm, the mean WS before IOL insertion was 2.21±0.03 mm in the fast subgroup and 2.21±0.02 mm in the slow subgroup, with no statistically significant difference (P=0.955). The mean WS after IOL insertion was 2.23±0.05 mm in subgroup BF and 2.25±0.06 mm in subgroup BS, with no statistically significant difference (P=0.836) ([Table 4]).

By comparing WS in subgroup BF before IOL insertion (2.21±0.03 mm) and after IOL insertion (2.23±0.05 mm), there was a statistically significant difference (tP=0.042).

By comparing WS in subgroup BS before IOL insertion (2.21±0.02 mm) and after IOL insertion (2.25±0.06 mm), there was a statistically significant difference (tP=0.008).

[Table 5] compared the need for hydration of the wound to ensure sealing between the four studied subgroups. In group A, there was a need for wound hydration in 35% of cases in the fast subgroup and in 65% of cases in the slow subgroup. The difference was not statistically significant (P=0.058). In group B, there was a need for wound hydration in 30% of cases in the fast subgroup and in 60% of cases in the slow subgroup. The difference was not statistically significant (P=0.057). Also, when comparing the AF and BF subgroups, the difference was not statistically significant (P=0.736). In addition, when comparing the AS and BS subgroups, the difference was not statistically significant (P=0.744). When the four subgroups were compared together regarding the need for hydration, there was no statistically significant difference (P=0.060).
Table 5 Comparison between the four studied groups according to hydration

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[Table 6] compared the SIA between the four studied subgroups. In group A, the SIA was 0.57±0.14 diopter in the fast subgroup and 0.59±0.14 diopter in the slow subgroup. The difference was not statistically significant (P=0.965). Similarly in group B, the SIA was 0.58±0.16 diopter in the fast subgroup and 0.60±0.18 diopter in the slow subgroup. The difference was not statistically significant (P=0.956). In addition, there was no statistically significant difference comparing SIA between the four subgroups (P=0.913).
Table 6 Comparison between the four studied groups according to astigmatism

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  Discussion Top


The effect of the speed of injection of the IOL on the wound was studied in two groups: group A with a 2.4-mm WS and group B with a 2.2-mm incision size.

The demographic data were almost homogeneous between the four subgroups, with no significant difference regarding age, sex, and laterality.

In addition, when the four subgroups were compared regarding the IOL power implanted, there was no statistically significant difference. This ensured homogeneity between the four subgroups regarding the effect of IOL power on wound enlargement.

In the present study, it was found that there is less impact on the surgical incision with fast IOL insertion than with slow insertion. This was found in the two studied groups (A and B).

In group A, there was no statistically significant difference when comparing the mean WS in the fast subgroup just before IOL insertion (2.41±0.03 mm) and just after IOL insertion (2.43±0.06 mm), whereas there was a statistically significant difference when comparing the mean WS in the slow subgroup just before IOL insertion (2.42±0.04 mm) and just after IOL insertion (2.46±0.06 mm). This means that the slow pass of the IOL through the wound enlarged it significantly, whereas the fast pass did not affect it.

In group B, there was a statistically significant difference when comparing the mean WS in the fast subgroup just before IOL insertion (2.21±0.03 mm) and just after IOL insertion (2.23±0.05 mm). The same was found in the slow subgroup, which was 2.21±0.02 mm before IOL insertion and 2.25±0.06 mm after IOL insertion, with a statistically significant difference. This means that in the 2.2-mm group both fast and slow insertion speeds caused a significant enlargement in the WS, although the degree of enlargement was more in the slow subgroups.

Other studies found wound construction and wound enlargement to be affected by various injector cartridges or insertion methods [8],[14]. Those studies found that the stress to the wound structure was greatest when the IOL passed through the wound.

A study conducted in Japan evaluated the effect of the speed of insertion of the IOL on the clear corneal wound structure [16]. This study found that the change in WS was significantly larger in the slow group when compared with the fast group. The studied WS was 2.4 mm only.

In a trial to understand the factors causing wound stretch and enlargement, several issues were postulated [15]. First, there is the issue of discontinuous movement of the IOL through the incision. By watching videos of IOL insertion using manual Monarch III injector, we can notice up to five brief pauses with no forward movement of the IOL along the incision. These pauses might allow the IOL to begin to re-expand within the incision.

At a slower speed of injection, there is more time for the IOL for more expansion, hence stretching the wound and causing enlargement. Second, we noticed that as we turned the screw handle of the manual injector we sometimes caused a small amount of rotation about the long z-axis of the device.

In the present study, we needed to hydrate the wound to achieve sealing in 65% of the slow subgroup in group A compared with only 35% of the fast subgroup. This was also the case in group B; we needed hydration in 60% of the slow subgroup compared with only 30% of the fast subgroup. Although all the comparisons were statistically nonsignificant, there were definitely more leaky wounds in the slow subgroups in both incision sizes, 2.4 and 2.2 mm, that needed hydration to ensure sealing. This is in accordance with the study by Ouchi, in which he found that the percentage of eyes that required corneal hydration to seal the wound was significantly higher in the slow insertion group than in the fast insertion group [16].

In the present study, the SIA ranged from 0.35 diopter as a minimum to 0.93 diopter as a maximum in both groups A and B and the two speeds fast and slow. There was no statistically significant difference among the four studied groups. This means that even with wound stretching and enlargement the effect on astigmatism induction was very little and nonsignificant.

In a study comparing the effect of rapidity of introduction of IOL on the SIA using 2.4-mm incision size, the mean SIA 4 weeks postoperatively was found to be 0.64±0.41 diopter in the fast group and 0.68±0.30 diopter in the slow group; this was not statistically significant [16]. This is in accordance with the present study results in group A with a 2.4 mm wound in which the mean SIA 1 week postoperatively was 0.57±0.14 diopter in the fast group and 0.59±0.14 diopter in the slow group, with no statistically significant difference.


  Conclusion Top


The present data indicate that in regard to IOL insertion using the injector system slow-speed IOL insertion induced more damage to the surgical wound than fast-speed insertion. Thus, the surgeon should insert the IOL quickly to lessen such damage.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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Mamalis N. From the editor: is smaller better? J Cataract Refract Surg 2003; 29:1049–1050.  Back to cited text no. 1
    
2.
Kohnen T, Dick B, Jacobi KW. Comparison of the induced astigmation after temporal clear corneal tunnel incision of different sizes. J Cataract Refract Surg 1995; 21:417–424.  Back to cited text no. 2
    
3.
Masket S, Wang L, Belani S. Induced astigmation with 22 and 3.0 mm coaxial phacoemulsification incisions. J Refract Surg 2009; 25:21–24.  Back to cited text no. 3
    
4.
Hayashi K, Yoshida M, Hayashi H. Postoperative corneal shape changes: microincision versus small-incision coaxial cataract surgery. J Cataract Refract Surg 2009; 35:233–239.  Back to cited text no. 4
    
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6.
Nichamin LD, Chang DF, Johnson SH, Mamalis N, Masket S, Packard RB, Rosenthal KJ, American Society of Cataract and Refractive Surgery Cataract Clinical Committee ASCRS white paper: what is the association between clear corneal cataract incisions and postoperative endophthalmitis? J Cataract Refract Surg 2006; 32:1556–1559.  Back to cited text no. 6
    
7.
Moreno-Montañés J, Maldonado MJ, García-Layana A, Aliseda D, Munuera JM Final clear corneal incision size for AcrySof intraocular lenses. J Cataract Refract Surg 1999; 25:959–963.  Back to cited text no. 7
    
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Kohnen T, Lambert RJ, Koch DD. Incision sizes for foldable intraocular lenses. Ophthalmology 1997; 104:1277–1286.  Back to cited text no. 8
    
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Kohnen T, Koch DD. Experimental and clinical evaluation of incision size and shape following forceps and injector implantation of a three-piece high-refractive-index silicone intraocular lens. Graefes Arch Clin Exp Ophthalmol 1998; 236:922–928.  Back to cited text no. 9
    
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Kohnen T, Kasper T. Incision sizes before and after implantation of 6-mm optic foldable intraocular lenses using Monarch and unfolder injector systems. Ophthalmology 2005; 112:58–66.  Back to cited text no. 10
    
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Kohnen T. Incision sizes with 5.5 mm total optic, 3-piece foldable intraocular lenses. J Cataract Refract Surg 2000; 26:1765–1772.  Back to cited text no. 11
    
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Mamalis N. Incision width after phacoemulsification with foldable intraocular lens implantation. J Cataract Refract Surg 2000; 26:237–241.  Back to cited text no. 13
    
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Kohnen T, Klaproth OK. Incision sizes before and after implantation of SN60WF intraocular lenses using the Monarch injector system with C and D cartridges. J Cataract Refract Surg 2008; 34:1748–1753.  Back to cited text no. 14
    
15.
Allen D, Habib M, Steel D. Final incision size after implantation of a hydrophobic acrylic aspheric intraocular lens: new motorized injector versus standard manual injector. J Cataract Refract Surg 2012; 38:249–255.  Back to cited text no. 15
    
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Ouchi M. Effect of intraocular lens insertion speed on surgical wound structure. J Cataract Refract Surg 2012; 38:1771–1776.  Back to cited text no. 16
    



 
 
    Tables

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



 

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