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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 109  |  Issue : 1  |  Page : 16-20

Refractive stability of low-cost intraocular lens following Nd:YAG capsulotomy


Ophthalmology Department, Faculty of Medicine, Al-Minia University, Al-Minia, Egypt

Date of Submission08-Aug-2015
Date of Acceptance27-Nov-2015
Date of Web Publication21-Oct-2016

Correspondence Address:
Heba R AttaAllah
32 Adnan El Maleky Str, Al-Minia 61111
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2090-0686.192745

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  Abstract 

Introduction
Low-cost intraocular lenses (IOLs) have been used in developing countries for many years. In a recent randomized trial, they were found comparable to high-end IOLs in terms of safety, visual outcomes, and posterior capsule opacification (PCO) formation. Our team observed occasional significant refractive changes following Nd:YAG capsulotomy for patients implanted with these IOLs. We aimed to assess the changes in refraction and the anterior chamber (AC) depth induced by Nd:YAG capsulotomy for PCO following implantation of a low-cost IOL.
Patients and methods
This prospective study was conducted on a cohort of sequential patients with PCO following uncomplicated phacoemulsification and implant of in-the-bag low-cost IOL. Changes in refraction (spherical equivalence, cylinder power, and cylinder axis) were assessed by means of subjective verification of autorefraction. Changes in AC depth were assessed by means of ultrasound biomicroscopy. Changes in cylinder power and axis were included to assess IOL tilt.
Results
A total of 50 consecutive eyes were enrolled. However, five eyes of three patients were lost to follow-up. A total of 45 eyes of 36 patients completed the pre-YAG and post-YAG assessments. An overall 66.7% of patients were female. An overall 25% had bilateral capsulotomy. The mean age at capsulotomy was 62.4±7.46 years. The mean duration since cataract extraction was 13.3±17.15 months. The mean IOL power was 20.4±2.43 D. No significant changes were found in spherical equivalence, axis of cylinder, and AC depth. However, a significant change in the cylinder power (mean change: 0.36±0.93 D, P=0.039) was observed.
Conclusion
Our study adds further confirmation on low-cost IOLs being a suitable alternative to high-end IOLs in developing countries and in outreach settings.

Keywords: capsulotomy, low-cost intraocular lens, Nd:YAG, refractive stability


How to cite this article:
Nassar MM, AttaAllah HR. Refractive stability of low-cost intraocular lens following Nd:YAG capsulotomy. J Egypt Ophthalmol Soc 2016;109:16-20

How to cite this URL:
Nassar MM, AttaAllah HR. Refractive stability of low-cost intraocular lens following Nd:YAG capsulotomy. J Egypt Ophthalmol Soc [serial online] 2016 [cited 2023 Jan 28];109:16-20. Available from: http://www.jeos.eg.net/text.asp?2016/109/1/16/192745


  Introduction Top


The number of cataract extractions, in developing countries, is steadily increasing due to increase in patients’ visual needs, in addition to improved surgical techniques and visual outcomes of cataract extraction. In public hospitals of deprived areas in Upper Egypt, patients are partially funded, with the hospital providing up-to-date phaco consoles and qualified surgeons. However, patients are likely required to self-provide their consumables. Therefore, the use of low-cost intraocular lenses (IOLs) has become the new standard.

Low-cost IOLs have been used in developing countries for many years. Unfortunately, their properties and biocompatibility have been generally missed in published literature. In 2008, Aravind et al.[1] published a review article on cataract surgery and IOL manufacturing in India. They acknowledged the importance of low-cost IOLs in India's management to improve cataract surgery rates and outcomes. Later on, a literature review on cataract surgery in developing countries was published by Khanna et al.[2]; they investigated difficulties faced in providing the service; however, only ‘affordable consumables’ have been mentioned, without focusing on IOLs per se.

In 2013, Constantinou et al. [3] compared the outcomes of a low-cost IOL (Tecsoft Flex lens) and the AcrySof 5A60AT lens (Alcon Inc.) for the treatment of age-related cataracts. Both IOLs were found to be comparable in terms of safety, visual outcomes, and posterior capsule opacification (PCO) formation. They concluded that low-cost IOLs are considered a suitable alternative [3].

Working in Upper Egypt, we have been using low-cost IOLs for many years. With more than 400 procedures performed monthly, we also perform around 25 Nd:YAG capsulotomy procedures per month. Our team has observed occasional significant refractive changes following Nd:YAG capsulotomies. In this study, we aimed to assess the changes in refraction and the anterior chamber (AC) depth induced by Nd:YAG capsulotomy for PCO following implantation of a low-cost IOL.


  Patients and methods Top


A prospective cohort of sequential patients attending Nd:YAG Capsulotomy Clinic in Minia University Hospital, Al-Minia, Egypt, were identified during the period from May 2013 to December 2013.

We included all patients who had uncomplicated phacoemulsification in our department with in-the-bag implantation of a low-cost Acrylic Hydrophilic IOL (Aquafold; Omni Lens Pvt Ltd, Ahmedabad, India). Other inclusion criteria were PCO interfering with daily activities and relatively clear cornea to facilitate autorefraction.

Pre-YAG and post-YAG assessment included full clinical ophthalmology examination and automated refraction using the Nidek ARK 900 autorefractor/keratometer (Nidek Co. Ltd, Maehama Hiroishi-Cho Gamagori Aichi, Japan), with subjective verification. Central AC depth (distance between the center of the corneal endothelial surface and the center of the anterior surface of the IOL) was assessed by means of ultrasound biomicroscopy (UBM) using UBM plus, model P45, Paradigm(R), Inc., Salt Lake city, Utah, USA) on a dilated pupil. Scans were taken through the central cornea and pupil, lining the probe as perpendicular as possible to the central corneal area. Only scans with optimal images (bright reflection from the corneal surfaces and the IOL surface) were used for measurement and the average of three measurements was recorded.

The patients subsequently underwent Nd:YAG laser capsulotomy using the VISULAS YAG III (Carl Zeiss Meditec, Jena, Germany). The procedure was performed by a single investigator (H.R.A.). In all patients, 12 mm Ocular Abraham Capsulotomy Lens (Ocular Instruments, Bellevue, Washington, USA) was used, aiming for a 4 mm capsulotomy and energy ranging between 0.8 and 1.5 mJ/pulse. All patients received a stat dose of eye drops brimonidine tartrate 0.2% half an hour before the procedure and eye drops Dexamethasone 0.1% (Isopto-Maxidex), Alcon-COUVREUR-Belgium three times a day for the following 4 days. Post-YAG assessment was completed after 4 weeks.

We studied the effects of Nd:YAG capsulotomy on IOL stability by assessing changes induced by the procedure on central AC depth, spherical equivalent, and astigmatism of best-corrected visual acuity. Changes in astigmatism, cylinder power, and axis were included to assess IOL tilt.

Consent was obtained from all patients using the standard local Nd:YAG laser consent forms, with additional consent for pre-YAG and post-YAG UBM measurement. Approval was obtained from the Local Research Ethics Committee, Faculty of Medicine, Minia University Hospitals. Descriptive statistics were performed using SPSS statistics for Windows, version 17.0 (SPSS Inc., Chicago, Illinois, USA). Means were compared using the Wilcoxon signed-rank test.


  Results Top


A total of 50 consecutive eyes were enrolled. However, five eyes of three patients were lost to follow-up. A total of 45 eyes of 36 patients completed the pre-YAG and post-YAG assessments; there were 24 (66.7%) female and 12 (33.3%) male patients. Nine (25%) patients underwent bilateral capsulotomies and 27 (75%) patients underwent unilateral capsulotomy.

Average age at the time of Nd:YAG capsulotomy was 62.4 ± 7.46 years (range: 50–72 years). Average duration since cataract extraction was 13.3 ± 17.15 months (range: 3–60 months). The mean power of implanted IOL was 20.4 ± 2.43 D (range: 17–24 D). Our results are presented in [Table 1].
Table 1: Results

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Nd:YAG capsulotomy preformed following implantation of low-cost IOL has resulted in the changes outlined in [Table 2] and [Figure 1],[Figure 2],[Figure 3],[Figure 4]. However, all changes, but cylinder power, were found to be insignificant ([Table 2]).
Table 2: Mean change and statistics

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Figure 1: Pre-YAG and post-YAG spherical equivalence.

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Figure 2: Pre-YAG and post-YAG cylinder power.

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Figure 3: Pre-YAG and post-YAG axis of cylinder (cyl).

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Figure 4: Pre-YAG and Post-YAG central anterior chamber (AC) depth.

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  Discussion Top


Refractive changes following Nd:YAG capsulotomy have been observed by many ophthalmologists. This rose the question of how stable is the IOL following the procedure? IOL movement following Nd:YAG capsulotomy can be explained by the same forces that are expected to enlarge the capsulotomy opening following Nd:YAG. These include tractional forces in the posterior capsule from the contractile properties of the microfilaments and the metaplastic lens epithelial cells as well as the tension caused by the haptic loops in the equatorial region. These forces become realigned to cause a longitudinal displacement of the IOL following Nd:YAG capsulotomy.[4] This movement was demonstrated in a few studies.[5],[6] However, no significant change in refraction was found by most investigators [5],[6],[7],[8],[9],[10].

Refractive stability following Nd:YAG capsulotomy has been thoroughly investigated. In 1995, Thornval and Naeser [4] studied its effect following extracapsular cataract extraction and found no change in AC depth or refraction. Since then, multiple investigators have studied the stability of IOL and refraction following Nd:YAG capsulotomy. All [5],[7],[8],[9],[10] but one [11] found no significant change.

Our results were found comparable to previous studies on high-end IOLs. We found no significant change in central AC depth or spherical equivalent following Nd:YAG capsulotomy.

To our knowledge, the only contradicting results were found in a study by Zaidi and Askari.[11] Their results found a significant decrease in AC depth and an accompanying significant myopic shift. These results could be explained from their methodology as the AC depth was measured using a contact A-scan ultrasound while the intraocular pressure medically reduced[11].

Different variables were also considered. In 1999, Findl et al.[5] investigated the effect of Nd:YAG on three different IOLs and found more backward movement with the plate haptic IOL. However, they concluded as follows: ‘Since the magnitude of IOL movement in this study population was small, a hyperopic shift in refraction after capsulotomy will usually be small and not clinically relevant’. Yilmaz et al.[9] and Karahan et al.[6] investigated the effect of capsulotomy size. The former found no effect and the latter observed an initial shift with larger capsulotomy size, which later stabilized.[6],[9] In 2012, Vrijman et al.[12] studied the effect of Nd:YAG on diffractive IOLs and concluded that Nd:YAG capsulotomy in patients with multifocal pseudophakia did not result in a change in refraction. However, in their study, 7% of eyes experienced a significant change in subjective refraction. This change was only −0.10 ± 0.27 D and it was explained by the authors as follows: ‘This change was small and the standard deviation is below the repeatability of the autorefraction, therefore, the statistical significance of this change reflects the large sample rather than a clinically relevant difference’ [12].

We assessed the behavior of low-cost IOL following Nd:YAG capsulotomy and found an insignificant effect of the procedure on central AC depth (mean change: 0.02 ± 0.14 mm) and spherical equivalence (mean change: 0.07 ± 0.51 D) (P = 0.630 and 0.425, respectively).

Interestingly, a significant change in the cylinder power (mean change: 0.36 ± 0.93 D, P = 0.039) was noted. However, there was no change in spherical equivalence or axis of cylinder, indicating no actual IOL tilt. Changes in astigmatism were previously documented by Hu et al.[7], who found an initial decrease in astigmatism, which later stabilized, and by Levy et al.[13], who studied higher order abrasions and found a significant decrease in ocular wave front aberrations, which accounted for a better optical quality after the procedure.

We acknowledge the small number of patients in our cohort. This resulted from our inclusion criteria of uncomplicated in-the-bag implantation of only one type of low-cost IOL along with a clear cornea. In addition, the absence of a control group is acknowledged as another limitation.


  Conclusion Top


In summary, our study adds further confirmation to the findings of Constantinou et al.[3] on low-cost IOLs being a suitable alternative to high-end IOLs in developing countries and in outreach settings. In addition, our study adds further proof on the safety and predictability of Nd:YAG capsulotomy.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Aravind S, Haripriya A, Sumara Taranum BS. Cataract surgery and intraocular lens manufacturing in India. Curr Opin Ophthalmol 2008; 19:60–65.  Back to cited text no. 1
[PUBMED]    
2.
Khanna R, Pujari S, Sangwan V. Cataract surgery in developing countries. Curr Opin Ophthalmol 2011; 22:10–14.  Back to cited text no. 2
    
3.
Constantinou M, Jhanji V, Jing X, Lamoureux EL, Boffa U, Taylor HR, Vajpayee RB. A randomized, single-center study of equivalence of 2 intraocular lenses used in cataract surgery. Ophthalmology 2013; 120:482–488.  Back to cited text no. 3
    
4.
Thornval P, Naeser K. Refraction and anterior chamber depth before and after neodymium: YAG laser treatment for posterior capsule opacification in pseudophakic eyes: a prospective study. J Cataract Refract Surg 1995; 21:457–460.  Back to cited text no. 4
    
5.
Findl O, Drexler W, Menapace R, Georgopoulos M, Rainer G, Hitzenberger CK, Fercher AF. Changes in intraocular lens position after neodymium: YAG capsulotomy. J Cataract Refract Surg 1999; 25:659–662.  Back to cited text no. 5
    
6.
Karahan E, Tuncer I, Zengin MO. The Effect of ND:YAG laser posterior capsulotomy size on refraction, intraocular pressure, and macular thickness. J Ophthalmol 2014; 2014:846385.  Back to cited text no. 6
    
7.
Hu CY, Woung LC, Wang MC, Jian JH. Influence of laser posterior capsulotomy on anterior chamber depth, refraction, and intraocular pressure. J Cataract Refract Surg 2000; 26:1183–1189.  Back to cited text no. 7
    
8.
Chua CN, Gibson A, Kazakos DC. Refractive changes following Nd:YAG capsulotomy. Eye (Lond) 2001; 15 ((Pt 3)):304–305.  Back to cited text no. 8
    
9.
Yilmaz S, Ozdil MA, Bozkir N, Maden A. The effect of Nd:YAG laser capsulotomy size on refraction and visual acuity. J Refract Surg 2006; 22:719–721.  Back to cited text no. 9
    
10.
Ozkurt YB, Sengör T, Evciman T, Haboğlu M. Refraction, intraocular pressure and anterior chamber depth changes after Nd:YAG laser treatment for posterior capsular opacification in pseudophakic eyes. Clin Exp Optom 2009; 92:412–415.  Back to cited text no. 10
    
11.
Zaidi M, Askari SN. Effect of Nd:YAG laser posterior capsulotomy on anterior chamber depth, intraocular pressure, and refractive status. Asian J Ophthalmol 2004; 5:2–5.  Back to cited text no. 11
    
12.
Vrijman V, van der Linden JW, Nieuwendaal CP, van der Meulen IJ, Mourits MP, Lapid-Gortzak R. Effect of Nd:YAG laser capsulotomy on refraction in multifocal apodized diffractive pseudophakia. J Refract Surg 2012; 28:545–550.  Back to cited text no. 12
    
13.
Levy J, Lifshitz T, Klemperer I, Knyazer B, Ashkenazy Z, Kratz A, Belfair N. The effect of Nd:YAG laser posterior capsulotomy on ocular wave front aberrations. Can J Ophthalmol 2009; 44:529–533.  Back to cited text no. 13
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2]



 

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