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 Table of Contents  
ORIGINAL ARTICLE
Year : 2013  |  Volume : 106  |  Issue : 3  |  Page : 123-128

The visual outcome of anisometropic amblyopia after laser-assisted in-situ keratomileusis surgery


Department of Ophthalmology, Faculty of Medicine, Suez Canal University Hospital, Ismailia, Egypt

Date of Submission05-Feb-2013
Date of Acceptance15-Aug-2013
Date of Web Publication28-Feb-2014

Correspondence Address:
Mervat E Elgharieb
Department of Ophthalmology, Faculty of Medicine, Suez Canal University Hospital, Ismailia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2090-0686.127344

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  Abstract 

Purpose
To evaluate the visual outcomes of patients with anisometropic amblyopia after laser in-situ keratomileusis (LASIK) surgery.
Patients and methods
LASIK was performed in 24 anisometropic amblyopic eyes of 24 patients. All eyes were amblyopic and received the standard amblyopia treatment (occlusion and/or optical penalization). The mean age of the patients was 21.62 ± 9.55 SD years, ranging from 6 to 42 years. The mean myopic error ± SD was -5.7 ± 2.25 (range from −11.5 to −3.25) and the mean hypermetropic ± SD was +3.5 ± 0.95.
Results
The preoperative mean uncorrected visual acuity ± SD was 0.11 ± 0.06 and became 0.56 ± 0.18, whereas the preoperative mean best corrected visual acuity was 0.39 ± 0.13 and became 0.57 ± 0.17 6 months postoperatively. Uncorrected visual acuity of all patients improved significantly about three or more lines in Snellen's chart. The best corrected visual acuity of about 79% of the patients improved by one or more lines in Snellen's chart.
Conclusion
LASIK is an effective option for the correction of high myopic or hypermetropic anisometropia.
Recommendations
LASIK surgery could be recommended in all types of anisometropic amblyopic patients in whom traditional management failed and who were intolerable to glasses or contact lenses. Amblypoia management should be continued postoperatively. Further studies are recommended to assess factors affecting anisometropic amblyopia management by LASIK, such as age, refraction, depth of amblyopia and response to conventional therapy.

Keywords: Amblyopia, failed traditional treatment of amblyopia, LASIK and anisometropia


How to cite this article:
El-Nahas HS, Elgharieb ME, Khalifa YM, Abou El-Ela SA. The visual outcome of anisometropic amblyopia after laser-assisted in-situ keratomileusis surgery. J Egypt Ophthalmol Soc 2013;106:123-8

How to cite this URL:
El-Nahas HS, Elgharieb ME, Khalifa YM, Abou El-Ela SA. The visual outcome of anisometropic amblyopia after laser-assisted in-situ keratomileusis surgery. J Egypt Ophthalmol Soc [serial online] 2013 [cited 2017 Dec 17];106:123-8. Available from: http://www.jeos.eg.net/text.asp?2013/106/3/123/127344


  Introduction Top


Amblyopia refers to a decrease in the best corrected visual acuity in an eye having no organic pathology [1]. One of the most important types of amblyopia is anisometropic amblyopia [2]. Anisometropic amblyopia is a unilateral decrease in visual acuity occurring with unequal, uncorrected refractive error that is present before 6 years of age [3]. Usually, the amount of amblyopia is determined by the depth of anisometropia [4]. The traditional treatment consists of the following:

  1. Correcting the refractive anomaly with spectacles or contact lenses.
  2. Occlusion therapy.
  3. Penalization therapy.


As the traditional treatment has many problems [5], a new option was introduced in the management of anisometropic amblyopia, which is laser in-situ keratomileusis (LASIK). This study was conducted to evaluate the visual outcome of patients with anisometropic amblyopia after LASIK surgery.


  Patients and methods Top


Patients with anisomertopic ambylopia visiting the Ophthalmic Out-patient Clinic, Suez Canal University Hospital, for excimer laser correction, who fulfilled the following criteria were included in the study: age above 5 years, all eyes were amblyopic and received the standard amblyopia treatment (occlusion and/or optical penalization), intolerant to contact lenses and spectacles, have a best corrected visual acuity (BCVA) of 6/6 (1.0) in the dominant eye and anisometropia with the difference between the two eyes more than three lines in Snellen's chart. Informed consent was obtained from all patients included in the study, conforming to local laws and in compliance with the principles of the Declaration of Helsinki and WHO guidelines. The research protocol was approved by the Faculty of Medicine Ethics Committee, Suez Canal University, Ismailia, Egypt.

Examinations included

  1. Visual acuity assessment by landolt C type chart: unaided and aided with spectacles.
  2. Manifest refraction and cycloplegic refraction (streak retinoscope and autorefractometer NIDEK AR 1600).
  3. BCVA.
  4. Slit-lamp examination for anterior segment evaluation.
  5. Intraocular pressure measurement by a Goldmann applanation tonometer.
  6. Fundus examination using an indirect ophthalmoscope with +20 or +30 D condensing noncontact lenses.
  7. Keratometry (Shin-Nippon).
  8. Schirmer's test.
  9. Ultrasound pachymetry.
  10. Corneal topography.


Procedure

Uncooperative children received general anaesthesia (intravenous without intubation with ketamine), whereas cooperative children, adults and middle-aged patients received topical anaesthesia using topical benoxinate hydrochloride 0.4% eye drops. LASIK was performed in 24 anisometropic amblyopic eyes of 24 patients with Hansatome microkeratome.

Postoperative treatment

Topical antibiotic and steroid eye drops were given in the form of gatifloxacin 0.3% (Zymar; Allergan), prednisolone acetate 1% (Pred Forte; Allergan) and Refresh Tears (Allergan) four times a day started immediately after LASIK; the topical steroids will then be withdrawn gradually over 1 month. Frequent use of artificial tears (Refresh Tears) was recommended for the first 3 months after LASIK surgery.

Follow-up examinations and outcome measures

Patients were followed up postoperatively on the first day, the first week, and the first month, and then every month up to 6 months. The follow-up examinations include the following:

  1. Uncorrected visual acuity (UCVA) and BCVA.
  2. Slit-lamp examination for anterior segment evaluation.
  3. Manifest refraction in the spherical equivalent. The residual error measured and full correction by glasses prescribed (if needed) based on the cycloplegic refraction.


Occlusion therapy continued postoperatively by occlusion of the dominant eye for about 4-6 h daily as long as possible until no further improvement could be obtained.


  Results Top


This study included 24 eyes of 24 patients with a mean age of 21.62 ± 9.55 SD years, ranging from 6 to 42 years. There were 14 male and 10 female patients. Sixteen of them were myopic and eight hypermetropic with or without astigmatism [Table 1].
Table 1: Age and sex distribution among the studied patients

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On comparing the UCVA and the BCVA of the target amblyopic eye and the fellow eye, a highly statistically significant difference was found [Table 2].
Table 2: A comparison of the preoperative uncorrected and the best corrected visual acuity between the target (amblyopic) and the fellow eye (nonamblyopic) among the studied patients

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On comparing the preoperative manifest refraction between both of the target myopic (amblyopic), the target hyperopic (amblyopic) and the sound eyes (fellow) among the studied patients, a highly statistically significant difference was found [Table 3].
Table 3: A comparison of the preoperative manifest refraction between both of the target myopic (amblyopic), target hyperopic (amblyopic) and sound eyes (fellow) among the studied patients

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The changes achieved in the UCVA over a follow-up period of 6 months revealed that there was a statistically significant difference between different stages of follow-up and the preoperative values [Table 4] and [Figure 1].
Figure 1:

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Table 4: The uncorrected visual acuity before and after operation among the studied patients

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The changes achieved in the BCVA over the 6 months of follow-up revealed that there was no statistically significant difference in the first day and the first week of follow-up as compared with the preoperative values, whereas there was a statistically significant difference noticed in the first month and the sixth month of follow-up [Table 5] and [Figure 2].
Figure 2:

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Table 5: The best corrected visual acuity before and after operation among the studied patients

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Uncorrected visual acuity of all patients improved significantly about three or more lines in Snellen's chart. The BCVA of about 79% of the patients improved by one or more lines in Snellen's chart [Table 6].
Table 6: A comparison of the best corrected visual acuity preoperatively and the uncorrected visual acuity 6 months postoperatively

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After 6 months, the postoperative manifest refraction of either the target myopic eye or the target hyperopic eye and the fellow eyes show no statistically significant difference [Table 7].
Table 7: Manifest refraction of either the target myopic eye or the target hyperopic eye and the fellow eyes 6 months postoperatively

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The keratometric and pachymetric readings changed obviously 6 months postoperatively [Table 8] and [Table 9].
Table 8: The keratometric reading before and after operation among the studied patients

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Table 9: Pachymetry before and after the operation among the studied patients

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The difference between anisometropia before and after LASIK showed extremely statistically significant differences [Table 10], which means that LASIK surgery helped in the reduction of anisometropia significantly.
Table 10: The difference between anisometropia before and after operation

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  Discussion Top


Amblyopia is a significant public health problem. It is one of the most common causes of preventable visual loss [6],[7]. One of the common causes of amblyopia is anisometropia. If the refractive error is corrected with glasses, improved vision in the amblyopic eye is usually associated with intolerable aniseikonia and may be diplopia [8],[9]. Contact lenses provided a better visual quality, a larger visual field and improved contrast sensitivity [5]. However, long-term use of contact lenses has potential infection risks and it is also not feasible for children. Therefore, the effect of traditional therapy for these patients is often poor.

In recent years, some researchers began to explore the application of excimer LASIK in the treatment of anisometropic amblyopia [10],[11],[12],[13],[14],[15],[16],17.

In this study, we evaluated the visual outcome of 24 patients with anisometropic amblyopia after LASIK surgery. The preoperative mean UCVA ± SD was 0.11 ± 0.06 and became 0.56 ± 0.18, whereas the preoperative mean BCVA was 0.39 ± 0.13 and became 0.57 ± 0.17 6 months postoperatively. Uncorrected visual acuity of all patients improved significantly about three or more lines in Snellen's chart. The BCVA of about 79% of the patients improved by one or more lines in Snellen's chart.

Dedhia and Behl [10], evaluated the efficacy and benefit of LASIK for the correction of anisometropic amblyopia. LASIK was performed in 21 eyes of 21 anisometropic amblyopes with a mean age of 27.71 ± 12.24 years. Three patients were less than 18 years of age and the follow-up period was 3 months, whereas in our study, the mean age of the patients was lower (21.62 ± 9.55 years) and the follow-up period was 6 months. The preoperative mean manifest spherical equivalent refraction in their study was −13.20 ± 3.84 D, and it significantly reduced to −0.78 ± 1.63 D, whereas the postoperative UCVA improved by two or more lines in all patients. It was the same as or better than the preoperative best spectacle-corrected visual acuity (BSCVA) in 95.2% of the eyes. In our study, the mean manifest spherical equivalent refraction was -5.7 ± 2.25 D for myopic patients and became −0.72 ± 0.8 D postoperatively. The postoperative UCVA also improved by two or more lines in all patients and was the same as or better than the preoperative BSCVA in 92% of the patients.

Sakatani et al. (11) evaluated the improvement in the BSCVA after LASIK in adult patients with amblyopia. Seven eyes (33.3%) experienced more than a one-line improvement in the postoperative UCVA compared with the preoperative BSCVA and nine eyes (42.8%) experienced more than a one-line improvement in postoperative BSCVA compared with the preoperative BSCVA. The BSCVA was unchanged in 11 eyes (52.4%) and was worse by two lines in one eye (4.8%); however, in our study, we had better results as five eyes (21%) experienced a two-line improvement in their postoperative UCVA compared with the preoperative BSCVA, 14 eyes (58%) experienced a one-line improvement in their postoperative UCVA compared with the preoperative BSCVA, three eyes had no improvement or worse UCVA compared with the preoperative BSCVA and two eyes were worse by one line.

In addition, the efficacy of LASIK in facilitating amblyopia management in children from 6 to 14 years of age was assessed in another study [12]. Their study included a higher percentage of hyperopic patients (56.7%) than our study (33.3%) as they worked on 42 children with hyperopic anisometropic amblyopia and 32 children with myopic anisometropic amblyopia. The hyperopic anisometropia correction ranged from +3.50 to +7.75 D (higher than our value of +2.25 to +5.0 D), and the mean postoperative anisometropia at 3 years was +0.56 ± 0.75 D (also higher than our value of +0.31 ± 0.51). The myopic anisometropia correction ranged from −15.75 to −5.00 D (higher than our value of −11.5 to −3.25), and the mean postoperative anisometropia at 3 years was −2.20 ± 1.05 D (also higher than our value of −0.83 ± 0.65).

Astel et al. [13] assessed the refractive error, the visual acuity and binocular results of laser-assisted subepithelial keratectomy (LASEK) for anisomyopia, anisohyperopia and anisoastigmatia in children with various levels of amblyopia secondary to anisometropic causes. In their study, 53 children with anisometropia underwent LASEK to correct the refractive difference between the eyes. The mean age at treatment was 8.4 years, and the mean preoperative anisometropic difference was 9.48 D in the anisomyopic group and 5.50 D in the anisohyperopic group, which reduced significantly to 2.43 and 2.33 D, respectively. 63.6% of the children had an improvement in the BCVA and the remainder had no noted change. Our study differs in using LASIK, and not LASEK, for the correction of anisometopic error. Our mean preoperative anisometropic difference was -5.03 ± 2.15 D in the anisomyopic group and +3.15 ± 0.77 D in the anisohyperopic group, which reduced significantly to −0.83 ± 0.65 D and +0.31 ± 0.51 D, respectively. Postoperative improvement in BCVA occurred in 79% of the patients.

In the study of Lin et al. [14], they concluded that LASIK for the correction of high anisometropia in children with monocular amblyopia may be safe and effective. Their study was conducted on 24 eyes (five myopes and 19 hypermetropes) with high unilateral anisometropic amblyopia, who underwent LASIK. The mean age of these children was 7.4 ± 1.9 years and ranged from 5 to 14 years. The mean preoperative UCVA was 0.06 ± 0.05 and was elevated significantly to 0.43 ± 0.33 postoperatively, whereas the mean preoperative BCVA was 0.26 ± 0.22 and was elevated postoperatively to 0.67 ± 0.40. The mean myopic spherical equivalent refraction was -8.01 ± 2.70 D for myopic anisometropic patients, whereas the postoperative value reduced significantly to -1.32 ± 2.47 D. For patients with hyperopic anisometropia, the preoperative mean spherical equivalent refraction was +7.35 ± 1.55 D, whereas the postoperative value reduced significantly to +3.30 ± 0.86 D.

Comparing their results with those of our study, our patients had a higher age range of 6-42 years. The mean preoperative UCVA in our study was slightly higher than that in the Lin and colleagues's study. It was 0.11 ± 0.06 preoperatively and was elevated postoperatively to 0.56 ± 0.18, which is also higher than their results. Our mean preoperative BCVA was 0.39 ± 0.13 and was elevated postoperatively to 0.57 ± 0.17, which was also higher than the Lin and colleagues's results. The preoperative mean myopic spherical equivalent refraction was -5.7 ± 2.25 D and became -0.72 ± 0.78 D postoperatively; however, the preoperative mean hyperopic spherical equivalent refraction was +3. 5 ± 0.95 D and became +0.68 ± 0.4 D postoperatively, which was lower than in the Lin and colleagues's study [14].

Assad et al. [15], evaluated the effects of LASIK in decreasing myopic anisometropia in 25 children, whose mean spherical equivalent refraction in the operated eye had reduced significantly from −9.08 ± 1.86 D preoperatively to −0.97 ± 1.16 D at 2 years postoperatively. The mean spherical equivalent myopic anisometropia was −7.75 ± 2.25 D preoperatively and −0.50 ± 0.21 D at 2 years postoperatively, representing a 93.5% reduction in anisometropia; however, in our study, 16 myopic patients had a mean spherical equivalent myopic anisometropia was -5.03 ± 2. 15 D preoperatively and −0.83 ± 0.65 D at 6 months postoperatively, which represented an 83.49% reduction in anisometropia. It seems that it was lower than the Assad et al. [15], percentage. Nine eyes gained five or more lines in BCVA, five eyes gained three or four lines, nine eyes gained two lines and two eyes that had no change in BCVA; however, in our study, four eyes gained two lines, 10 eyes gained one line, one eye had no change and one eye worsened by one line.

In another study [16], the correction of refractive error by LASIK to improve the BCVA in anisometropic amblyopic eyes was assessed. It included 20 anisometropic amblyopic eyes of 20 patients who had undergone the LASIK procedure. The average age of the patients was 28.00 ± 7.91 years, ranging from 16 to 42 years (a wider range in our study: '6-42 years'). Sixteen eyes (80%) gained one to five lines of best corrected Snellen's visual acuity, whereas the remaining four eyes (20%) had the same BCVA as preoperatively. No eye had lost any line of best corrected visual acuity; however, in our study, 19 eyes (79%) gained one to two lines of best corrected Snellen's visual acuity, three eyes (13%) had the same BCVA as preoperatively and two eyes (8%) lost one line.

All previous studies concluded that LASIK surgery for anisometropic amblyopia could be a safe and effective choice in children after failed conventional therapy and that it decreased anisometropia in the adult group. In all cases, amblypoia management in the form of occlusion and/or penalization was continued in conjunction to anisometropic treatment by LASIK.


  Conclusion Top


In this study, we concluded that LASIK is an effective option for the correction of high myopic or hypermetropic anisometropia. It improved visual acuity in anisometropic patients who were unable to tolerate conventional methods of treatment or in whom these methods failed, eliminating anisometropia and alleviating aniseikonia, leading to more effective reversal of any residual amblyopia with patching and atropine, and finally, it has a high success rate.


  Recommendations Top


It is important to start amblyopia management as early as possible with traditional methods to prevent its severity from increasing. LASIK surgery could be recommended to be a line of treatment in all types of anisometropic amblyopic patients in whom traditional amblypoia management failed to correct amblypoia and in all patients who are intolerable to glasses or contact lenses. Amblypoia management should be continued postoperatively if possible to correct any residual amblyopia. Further studies are recommended to assess factors affecting amblyopia management by LASIK, such as age, refraction, depth of amblyopia and response to conventional therapy.


  Acknowledgements Top


Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.Von Noorden GK. Amblyopia: a multidisciplinary approach. Proctor lecture. Invest Ophthalmol Vis Sci 1985; 26 :1704-1716.  Back to cited text no. 1
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2.Von Noorden GK Classification of amblyopia. Am J. Ophthalmol 1967; 63 :238-244.  Back to cited text no. 2
    
3.Ciuffreda KJ, Levi D, Selenow A. Amblyopia: basic clinical aspects. Stoneham: Butterworth-Heinemann. 1991. p. 1-38.  Back to cited text no. 3
    
4.Townstead AM, Holmes JM, Evans LS. Depth of anisometropic amblyopia and difference in refraction. Am J Ophthalmol 1993; 116 :431-436.  Back to cited text no. 4
    
5.Freeman MI. Spectacles vs contact lenses in the correction of unilateral axial myopia. Arch Ophthalmol 1992; 110 :180.  Back to cited text no. 5
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6.Weakley DJr. The association between nonstrabismic anisometropia, amblyopia, and subnormal binocularity. Ophthalmology 2001; 108 :163-171.  Back to cited text no. 6
    
7.Sjöstrand J, Abrahamsson M. Prevention of amblyopia and the concept of cure. Eur J Ophthalmol 1997; 7 :121-129.  Back to cited text no. 7
    
8.Cobb DJ, Russell K, Cox A. Factors influencing visual outcome in anisometropic amblyopes. Br J Ophthalmol 2002; 86 :1278-1281.  Back to cited text no. 8
    
9.Woodruff G, Hiscox F, Thompson JR, et al. The presentation of children with amblyopia. Eye 1994; 8 :623-626.  Back to cited text no. 9
[PUBMED]    
10.NC Dedhia, S Behl. Laser in situ keratomileusis for anisometropic amblyopia. J Refract Surg 2000; 16(Suppl) :S264-S267.  Back to cited text no. 10
    
11.Sakatani K, Jabbur NS O′Brien TP. Improvement in best corrected visual acuity in amblyopic adult eyes after laser in situ keratomileusis. J Cataract Refract Surg 2004; 30 :2517-2521.  Back to cited text no. 11
    
12.Yin ZQ, Wang H, Yu T, Ren Q, Chen L. Facilitation of amblyopia management by laser in situ keratomileusis in high anisometropic hyperopic and myopic children. J AAPOS 2007; 11 :571-576.  Back to cited text no. 12
[PUBMED]    
13.Astle WF, Rahmat J, Ingram AD, Huang P. Laser-assisted subepithelial keratectomy for anisometropic amblyopia in children. J Cataract Refract Surg 2007; 33 :2028-2034.  Back to cited text no. 13
    
14.Lin XM, Wang Z, Yang B, et al. Long-term efficacy of excimer laser in situ keratomileusis in the management of children with high anisometropic amblyopia. Chin Med J 2009; 122 :813-817.  Back to cited text no. 14
[PUBMED]    
15.Assad AG, Ashraf IM, Ehab HN, et al. Laser in situ keratomileusis for treated myopic anisometropic amblyopia in children. Saudi J Ophthalmol 2010; 24 :3-8.  Back to cited text no. 15
    
16.Tamer AR, Olfat AH. Evaluation of improvement of best corrected visual acuity following LASIK treatment in anisometropic amblyopia. Aust J Basic Appl 2011; Sci 5:23-29.  Back to cited text no. 16
    


    Figures

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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10]



 

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Abstract
Introduction
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